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  • 1
    Digitale Medien
    Digitale Medien
    Differential capacitance studies of the specific adsorption of thiosulfate on silver (1998)
    Springer
    Journal of applied electrochemistry 28 (1998), S. 993-998 
    Details
    ISSN: 1572-8838
    Schlagwort(e): thiosulfate ; silver ; adsorption ; differential capacitance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract The differential capacitance of a polycrystalline Ag electrode was measured in a NaClO4 electrolyte containing Na2S2O3 at concentrations ranging from 0.1 to 20mm and at electrode potentials ranging from −0.9 to −0.3V vs SCE. The differential capacitance measurements were analysed to obtain the surface coverage of specifically adsorbed thiosulfate (S2O32−) as a function of both electrode potential and bulk concentration. The various forms for the adsorption isotherm at an electrochemical interface which are commonly employed are reviewed and discussed. The adsorption behaviour is best explained by the formation of image dipoles by the specifically adsorbed ions, whose energetic interactions are then dominated by repulsion of like dipoles. The adsorption data is quantitatively fit to an adsorption isotherm for interacting dipoles, yielding an effective dipole moment of 0.72D for the system S2O32−/Ag.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1003405329562
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  • 2
    Digitale Medien
    Digitale Medien
    Modelling of cyclic voltammograms for two-step metal deposition on an inert electrode with adsorption (1998)
    Springer
    Journal of applied electrochemistry 28 (1998), S. 819-825 
    Details
    ISSN: 1572-8838
    Schlagwort(e): adsorption ; experimental design ; metal electrodeposition ; modelling ; voltammetry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract Chromium deposition on an inert electrode is a complex process. To gain a better understanding of phenomena involved in multistep reactions we have studied such a mechanism and developed Voltasim, a new software that simulates cyclic voltammograms for a two-step metal deposition with adsorption. In addition, Voltasim is suitable for either reversible or quasi-reversible or irreversible reactions. The software was validated with experimental results obtained for the chromium deposition case. Data fitting was achieved using a screening design of experiments involving 12␣parameters.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1003424123260
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  • 3
    Digitale Medien
    Digitale Medien
    An integrated flow reactor-membrane filtration system for heterogeneous photocatalysis. Part I: Experiments and modelling of a batch-recirculated photoreactor (1999)
    Springer
    Journal of applied electrochemistry 29 (1999), S. 533-539 
    Details
    ISSN: 1572-8838
    Schlagwort(e): adsorption ; dye photooxidation ; titanium dioxide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract A two-part study was undertaken to examine the feasibility of combining a batch-recirculated photoreactor with a hollow-fibre membrane based ultrafiltration unit for heterogeneous photocatalysis applications. Methylene Blue (MB) and titanium dioxide (Degussa, P-25) were used as the test substrate and photocatalyst respectively for this study. This paper, which forms Part I of this study, describes the influence of MB concentration, recirculation flow rate, TiO2 dose, solution volume in the reservoir and solution pH on the photocatalytic reaction rate. The dark adsorption of MB on the TiO2 particle surface was also analysed. The combination of the reservoir and the annular reaction vessel could be modelled as a continuous flow stirred tank in series with a plug-flow reactor. This model predicts that the reaction rate should increase with a decrease of solution volume in the reservoir, both in the low and high substrate concentration regimes of the Langmuir–Hinshelwood kinetics formalism. This prediction was borne out by the experimental data for the low concentration regime. Part II of this series will describe experiments and modelling of the UF unit, and the operation of the combined system, respectively.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026418208733
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  • 4
    Digitale Medien
    Digitale Medien
    3,5-bis(n-Hydroxyphenyl)-4-amino-1,2,4-triazoles and 3,5-bis(n-aminophenyl)-4-amino-1,2,4-triazoles: a new class of corrosion inhibitors for mild steel in 1m HCl medium (1999)
    Springer
    Journal of applied electrochemistry 29 (1999), S. 1073-1078 
    Details
    ISSN: 1572-8838
    Schlagwort(e): acidic media ; adsorption ; corrosion inhibitors ; electrochemical impedance spectroscopy ; mild steel ; triazoles
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract A new class of corrosion inhibitors, namely, 3,5-bis(n-hydroxyphenyl)-4-amino-1,2,4-triazoles and 3,5-bis(n-aminophenyl)-4-amino-1,2,4-triazoles which have been labelled n-HPAT and n-APAT has been synthesized. The influence of aminotriazoles on the corrosion of mild steel in 1m HCl has been studied using weight loss and electrochemical impedance spectroscopy. Results obtained show that these compounds are very good anodic inhibitors. The adsorption of these aminotriazoles is found to obey Langmuir adsorption isotherm.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1003421111890
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  • 5
    Digitale Medien
    Digitale Medien
    Adsorption of SO2 from Wet Mixtures on Hydrophobic Zeolites (1998)
    Springer
    Adsorption 4 (1998), S. 25-33 
    Details
    ISSN: 1572-8757
    Schlagwort(e): hydrophobic zeolites ; breakthrough curves ; adsorption ; binary mixtures ; modeling ; overall mass transfer ; roll-up
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract Breakthrough curve measurements of SO2 and water vapor were carried out on a number of selected mordenite and pentasil zeolites from their binary and ternary mixtures with CO2 at 50 and 100°C. SO2 capacities of these samples were found to be significantly reduced by the presence of water. Competitive adsorption led to unusually high overshoot peaks of SO2 breakthrough curves. On the other hand, SO2 was found to displace water on the samples with very high silica to alumina ratio. A linear driving force, isothermal model was used to predict the breakthrough curves. Langmuir and extended Langmuir equilibrium models were used to describe the equilibrium properties of water and SO2, respectively. The overall mass transfer resistance obtained from the model was compared to the values calculated from a simplified biporous adsorbent model to shed some light on the adsorption kinetics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008883219403
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  • 6
    Digitale Medien
    Digitale Medien
    Neural Network Modeling of Adsorption of Binary Vapour Mixtures (1999)
    Springer
    Adsorption 5 (1999), S. 183-192 
    Details
    ISSN: 1572-8757
    Schlagwort(e): adsorption ; activated carbon ; neural network ; ideal adsorption solution theory
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract Three neural network models were used for prediction of adsorption equilibria of binary vapour mixtures on an activated carbon. The predictions were compared both with published experimental data and calculated values from the Ideal Adsorption Solution (IAS) model. The neural network was trained using both binary and single component experimental adsorption data. Even for a limited number of data points (about 60) the network models were capable of approximating experimental data very precisely.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008977528474
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  • 7
    Digitale Medien
    Digitale Medien
    Pressure Effects in Adsorption Systems (1999)
    Springer
    Adsorption 5 (1999), S. 261-278 
    Details
    ISSN: 1572-8757
    Schlagwort(e): adsorption ; concentrated systems ; pressure transients ; flow transients
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract A study of the occurrence of large pressure and flow transients when a strongly adsorbed gas is fed to a column which is initially loaded with a lightly adsorbed gas is presented here. Under certain conditions, these transients can cause premature breakthrough and change the shape of the breakthrough curve. This will result in improper estimation of adsorption parameters by the dynamic column loading method and lower apparent adsorption capacity in a full scale unit. A data acquisition system was used to record the pressure and flow transients. An isothermal PDE model developed to study these transients agreed reasonably well with the nonisothermal experimental results. The PDE model predicts that pressure and flow transients will occur during step and pulse~tests conducted to obtain adsorption and mass transfer parameters by the chromatographic method. For instance, lower adsorption capacity will be realized during step tests due to lowering in column pressure. Oscillations were observed when columns are connected in series. The PDE model also predicts these oscillations. Simulations indicate that the extent of oscillations is dependent on the dead volume between columns.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008955828900
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  • 8
    Digitale Medien
    Digitale Medien
    Adsorption and reduction of CO2 on 12-tungstophosphoric and 12-molybdophosphoric acids in the absence of added reductants (1998)
    Springer
    Catalysis letters 52 (1998), S. 163-170 
    Details
    ISSN: 1572-879X
    Schlagwort(e): carbon dioxide ; adsorption ; reduction ; dissociation ; 12-tungstophosphoric acid ; 12-molybdophosphoric acid
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract 12-tungstophosphoric and 12-molybdophosphoric acids are capable of sorbing and reducing CO2 without the presence of added reductants. The adsorbed CO2 (physisorbed as CO2) desorbs from the acids and salts at low temperatures (50–200°C). Carbon dioxide also desorbs only from the acids at high temperatures (500–600°C), suggesting the direct or indirect involvement of the protons in the process and the importance of the Keggin unit as well. Raman and DRIFTS results show that the species responsible for the evolution of CO2 (at high temperatures) are carbonaceous in nature. Carbon deposits extract the anionic oxygen atoms from the Keggin units during the high-temperature desorption process. The extraction of anionic oxygen atoms by carbon is confirmed using labeled carbon dioxide. The spectroscopic data imply that carbon exists on the surface as such but, additionally, as either carbon or CO2 bound to the terminal oxygen atoms of the Keggin anion.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019048209735
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  • 9
    Digitale Medien
    Digitale Medien
    IR study of reaction of 2‐butene adsorbed on deuterated ZSM‐5 and mordenite (1998)
    Springer
    Catalysis letters 53 (1998), S. 215-220 
    Details
    ISSN: 1572-879X
    Schlagwort(e): FT‐IR ; adsorption ; butene ; ZSM‐5 ; mordenite
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Reactions of cis‐ and trans‐2‐butene adsorbed on deuterated ZSM‐5 and mordenite were studied by IR spectroscopy below 300 K. 2‐butene molecules hydrogen‐bonding to Brønsted acid sites (OD) reacted when the temperature was increased above 250 and 230 K on D‐ZSM‐5 and D‐mordenite, respectively. H/D isotope exchange reaction of Brønsted acidic hydroxy groups accompanied the isomerization of cis‐ to trans‐2‐butene, and then dimerization of trans‐2‐butene followed on ZSM‐5, while rapid formation of paraffinic alkoxy groups was dominantly observed on mordenite.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019086712887
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  • 10
    Digitale Medien
    Digitale Medien
    Sorption Equilibria and Kinetics of Hydrocarbons onto Activated Carbon Samples Having Different Micropore Size Distributions (1999)
    Springer
    Adsorption 5 (1999), S. 25-37 
    Details
    ISSN: 1572-8757
    Schlagwort(e): micropore size distribution ; activated carbon ; adsorption ; desorption ; equilibrium ; kinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract This paper deals with the prediction of adsorption equilibrium and kinetics of hydrocarbons onto activated carbon samples having different micropore size distribution (MPSD). The microporous structure of activated carbon is characterised by the distribution of slit-shaped micropores, which is assumed to be the sole source of surface heterogeneity. The interaction between adsorbate molecule and pore walls is described by the Lennard-Jones potential theory. Different adsorbates have access to different pore size range of activated carbon due to the size exclusion, a phenomenon could have a significant influence on both multicomponent equilibria and kinetics. Activated carbons with three different MPSDs are studied with ethane and propane as the two model adsorbates. The Heterogeneous Macropore Surface Diffusion model (HMSD) is employed to simulate adsorption kinetics. The simulation results show that the MPSD is an important factor affecting both the multicomponent equilibria and kinetics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026481704926
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  • 11
    Digitale Medien
    Digitale Medien
    Propane and oxygen action on NOx adspecies on low-exchanged Cu-ZSM-5 (1998)
    Springer
    Catalysis letters 51 (1998), S. 27-40 
    Details
    ISSN: 1572-879X
    Schlagwort(e): NO ; adsorption ; Cu-ZSM-5 ; TPD ; nitrosopropane ; N2O
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A surface intermediate with a C/N ratio close to 3 has been shown by TPD to form at co-adsorption of NO and propane as well as NO, propane and O2 on low-exchanged Cu-ZSM-5. The adsorption of NO, propane and oxygen has been studied to evaluate their effect on the formation of this complex. Its formation is accompanied by a decrease in the concentration of surface nitrite–nitrate. The kinetics of nitrite–nitrate adspecies formation as a function of the reagents concentration and temperature has been investigated. Some NO adspecies have been found to decompose yielding N2O.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019024715245
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  • 12
    Digitale Medien
    Digitale Medien
    Density functional theory (DFT) and microcalorimetric investigations of CO adsorption on Pt clusters (1998)
    Springer
    Catalysis letters 51 (1998), S. 139-147 
    Details
    ISSN: 1572-879X
    Schlagwort(e): microcalorimetry ; carbon monoxide ; adsorption ; platinum ; DFT
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Microcalorimetric measurements were conducted at 573 K of CO adsorption on Pt clusters supported in L-zeolite. The measured heat of CO adsorption is 175 kJ/mol, and the heat decreases to 90 kJ/mol near saturation coverage. Quantum chemical calculations were performed using density functional theory to study the interaction of CO with 10-atom Pt clusters. The heat of CO adsorption on atop-sites is calculated to be 209 kJ/mol, while a lower heat of 142 kJ/mol is calculated for CO on bridge-sites. These values decrease to 197 and 102 kJ/mol for population of two atop-sites and two bridge-sites, respectively, on the same Pt10 cluster. The heat of adsorption decreases to 157 kJ/mol when six CO molecules adsorb on six atop-sites of the cluster. The calculated initial heat of CO adsorption on Pt10 clusters is in agreement with experimental and theoretical values reported for CO adsorption on Pt single-crystal surfaces. The higher heat of CO adsorption at atop-sites may be caused by more σ-donation from CO to sp orbitals of Pt for atop-sites. The heat of CO adsorption on bridge-sites becomes higher on negatively charged platinum clusters. The calculated C-O stretching frequencies for charged and neutral platinum clusters agree with experimental data.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019038512945
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  • 13
    Digitale Medien
    Digitale Medien
    Partial oxidation of propene over metal oxide catalysts pretreated with NO2 (1998)
    Springer
    Catalysis letters 53 (1998), S. 73-76 
    Details
    ISSN: 1572-879X
    Schlagwort(e): nitrogen dioxide ; titania ; propene ; selective oxidation ; adsorption
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Titania pretreated with NO2 has been found to catalyze the partial oxidation of propene into oxygenates such as acetone and acrolein at around 623 K, while fresh TiO2 produces only carbon oxides. Temperature‐programmed desorption (TPD) revealed that nitrogen oxides adsorbed on TiO2 are stable at temperatures below 673 K. Even after the propene oxidation at 573 K for 2 h, nitrogen oxides were confirmed still to exist on the TiO2 surface. At temperatures higher than 673 K, however, the desorption and/or the reduction of the adsorbed nitrogen oxides took place, and concomitantly the catalytic ability giving oxygenates disappeared.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019010023365
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  • 14
    Digitale Medien
    Digitale Medien
    FTIR spectroscopic evidence of formation of geminal dinitrogen species during the low-temperature N2 adsorption on NaY zeolites (1999)
    Springer
    Catalysis letters 58 (1999), S. 21-26 
    Details
    ISSN: 1572-879X
    Schlagwort(e): adsorption ; adsorption isotherms ; dinitrogen ; FTIR spectroscopy ; geminal species ; NaY ; nitrogen ; zeolites
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Adsorption of N2 on NaY zeolites at 85 K and equilibrium pressures higher than 1 kPa results in the formation of geminal dinitrogen complexes characterized by an IR band at 2333.5 cm−1 (2255.4 cm−1 after adsorption of 15N2). With decreasing equilibrium pressure the complexes tend to loose one N2 ligand, thus forming linear species characterized by an IR band at 2336.8 cm−1 (2258.7 cm−1 after adsorption of 15N2). All species disappear completely after evacuation. Co-adsorption of N2 and CO revealed that the dinitrogen complexes are formed on Na+ cations. The changes in the concentrations of the linear and geminal N2 species with the changes in the equilibrium pressure are excellently described by equations of adsorption isotherms proposed earlier for mono- and di-carbonyls.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019040825491
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  • 15
    Digitale Medien
    Digitale Medien
    The detailed kinetics of the adsorption of hydrogen on polycrystalline copper studied by reactive frontal chromatography (1999)
    Springer
    Catalysis letters 59 (1999), S. 151-155 
    Details
    ISSN: 1572-879X
    Schlagwort(e): hydrogen ; copper ; activation energy ; adsorption ; sticking probability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The coverage-dependent sticking probabilities of molecular hydrogen on polycrystalline copper supported on alumina have been determined in the temperature range 213–273 K by analysis of the hydrogen frontal adsorption line shape. In this temperature range the initial sticking probabilities increase from 8× 10−13 (213 K) to 1.3× 10−10 (273 K). The overall activation energy to adsorption has been found to be 42 kJ mol−1. The application of reactive frontal chromatography for the measurement of hydrogen sticking probabilities on copper is a novel variant of the N2O reactive frontal chromatographic method, developed for the measurement of copper surface areas. Its use here shows that reactive frontal chromatography may be applied generally to any adsorbate/adsorbent system involving activated adsorption and low sticking probabilities.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019028806778
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  • 16
    Digitale Medien
    Digitale Medien
    Ethylene adsorption on Pt/Au/SiO2 catalysts (1999)
    Springer
    Catalysis letters 60 (1999), S. 1-9 
    Details
    ISSN: 1572-879X
    Schlagwort(e): microcalorimetry ; IR ; platinum ; gold ; ethylene ; CO ; adsorption ; quantum chemical calculations ; DFT
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Ethylene adsorption on a Pt/Au/SiO2 catalyst (2 wt% Pt; Au/Pt atomic ratio of 10) was studied using adsorption microcalorimetry and FTIR spectroscopy. Ethylene adsorption at 300 K on Pt/Au/SiO2 produced π‐bonded, di‐σ‐bonded, and ethylidyne species with an initial heat of 140 kJ/mol, compared to a heat of 157 kJ/mol for Pt/SiO2 on which only ethylidyne species formed. At 203 and 263 K, ethylene adsorbed on Pt as well as on Au surface atoms for the Pt/Au/SiO2 catalyst. Quantum chemical, DFT calculations indicate that Au exerts a significantly smaller electronic effect on Pt than does addition of Sn to Pt.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019038503569
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  • 17
    Digitale Medien
    Digitale Medien
    Prospects for detecting metal–adsorbate vibrations by sum‐frequency spectroscopy (1999)
    Springer
    Catalysis letters 61 (1999), S. 7-13 
    Details
    ISSN: 1572-879X
    Schlagwort(e): sum‐frequency spectroscopy ; Pt(111) ; carbon monoxide ; adsorption ; far‐infrared ; free‐electron laser
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Sum‐frequency spectroscopy (SFS) was used in an attempt to detect the platinum–carbon vibration of CO adsorbed on Pt(111). The international free‐electron laser FELIX at the FOM Institute, Rijnhuizen, provided the required tunable far‐infrared (19–23 µm) source, while complementary measurements in the C–O stretch region (4.7–5.1 µm) were performed at the University of Oxford with a conventional nanosecond laser system. Ordered Pt(111) surfaces were prepared by the H2/O2 flame annealing approach and CO monolayers were produced by exposure of the Pt crystal to gaseous CO in a flow reactor. The monolayers were characterized by sum‐frequency (SF) measurements of the v C-O vibrational frequency. The CO adsorbed primarily in the terminal (atop) configuration, with a v C-O frequency of around 2078 cm−1. In the far‐IR region, the non‐resonant background from the Pt substrate could readily be detected by SFS, but there was no evidence for the v Pt-CO mode. Direct laser‐induced desorption and thermal desorption of CO are unlikely under the experimental conditions. It is therefore probable that the intrinsic cross‐section of the Pt–CO mode is too low for easy detection by SFS. The implications for the use of SFS to detect metal–adsorbate vibrational modes are discussed in light of these findings.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019056402177
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  • 18
    Digitale Medien
    Digitale Medien
    Effect of water on the reduction of NOx with propane on Fe‐ZSM‐5. An FTIR mechanistic study (1999)
    Springer
    Catalysis letters 62 (1999), S. 35-40 
    Details
    ISSN: 1572-879X
    Schlagwort(e): Fe‐ZSM‐5 ; carbon monoxide ; FTIR spectroscopy ; nitrates ; nitrogen monoxide ; selective catalytic reduction ; adsorption ; zeolites
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Adsorption of NO on Fe‐ZSM‐5 leads to formation of Fen+–NO (n = 2 or 3) species (1880 cm-1), Fe2+(NO)2 complexes (1920 and 1835 cm-1) and NO+ (2133 cm-1). Water strongly suppresses the formation of NO+ and Fen+(NO)2 and more slightly the formation of Fen+ –NO. Introduction of oxygen to NO converts the nitrosyls into surface nitrates (1620 and 1575 cm-1) and this process is almost unaffected by water. The nitrates are thermally stable up to ca. 300°C, but readily interact with propane at 200°C, thus forming surface C–H–N–O deposit (bands in the 1700–1300 cm-1 region). Here again, water does not hinder the process. The C–H–N–O deposit is relatively inert (it does not interact with NO or NO + O2 at ambient temperature) but, at temperatures higher than 250 °C, it is decomposed to NCO- species (bands at 2215 (Fe–NCO) and 2256 cm-1 (Al–NCO)). In the presence of water, however, the Fe–NCO species only are formed. At ambient temperature the NCO- species are inert towards NO and O2, but easily react with a NO + O2 mixture. The mechanism of the selective catalytic reduction of nitrogen oxides on Fe‐ZSM‐5 and the effect of water on the process are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019034619440
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  • 19
    Digitale Medien
    Digitale Medien
    A Study of Adsorption of Water Vapour on Wool under Static and Dynamic Conditions (1998)
    Springer
    Adsorption 4 (1998), S. 63-73 
    Details
    ISSN: 1572-8757
    Schlagwort(e): wool ; water vapour ; adsorption ; diffusion ; column dynamics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract Adsorption of water vapour on wool provides not only textile comfort, but also convenience in transportation due to increase in its bulk density. The adsorption and desorption isotherms of water vapour for wool were determined by both volumetric technique using a Coulter Omnisorp 100CX instrument and gravimetric method employing a Cahn 2000 electronic microbalance. Adsorption isotherm fitting to B.E.T. model and hysteresis on desorption was observed. The average effective diffusion coefficient of water in wool was found to be 8.4 × 10-14 m2s-1 at 25°C from gravimetric data. The effects of packing height and air velocity on the breakthrough curves were also investigated in the wool packed columns. For pseudo first order model, k values changing between 0.33 × 10-6 − 69 × 10-6 s-1 was obtained for 2.2–6.4 cm s-1 air velocity and 0.05–0.20 m packing height ranges.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008839404382
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  • 20
    Digitale Medien
    Digitale Medien
    Effects of Surface Oxygen of Activated Carbon on Alkaloid Adsorption: A Molecular Dynamics Simulation Study (1999)
    Springer
    Adsorption 5 (1999), S. 97-108 
    Details
    ISSN: 1572-8757
    Schlagwort(e): adsorption ; molecular simulation ; activated carbon ; surface oxygen ; alkaloids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract The influence of the density and the type of surface oxygen on the adsorption of berberine alkaloid onto activated carbon was investigated using the molecular dynamics simulation method in vacuum. The carbon surface consisted of a basal plane of graphite and surface oxygen groups which were bonded on the graphite plane in a regular square array with various densities. Two types of surface oxygen groups, =O and —OH, were employed. The simulation results showed that the berberine alkaloids were favorable to be adsorbed on the negative charged carbon surfaces. It was indicated that the vdw attraction of the carbon surface to the alkaloid molecule dominates the adsorption only at the lower surface density of oxygen. It is also indicated that a good adsorptive selectivity for a certain berberine alkaloid can be obtained by controlling the density of surface oxygen. The adsorption simulation of berberine alkaloids onto activated carbon in the presence of water was also carried out by using a dome-shape molecular model for presenting the alkaloid/water/carbon system. It was found that the adsorption of berberine alkaloids on the activated carbon which has a higher density of surface oxygen was strongly inhibited by the presence of water.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026479130851
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  • 21
    Digitale Medien
    Digitale Medien
    Pure and Binary Gas Adsorption Equilibria and Kinetics of Methane and Nitrogen on 4A Zeolite by Isotope Exchange Technique (1999)
    Springer
    Adsorption 5 (1999), S. 145-158 
    Details
    ISSN: 1572-8757
    Schlagwort(e): kinetics ; isotope-exchange ; nitrogen ; adsorption ; methane ; zeolite ; equilibria
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract The Isotope Exchange Technique (IET) was used to simultaneously measure pure and binary gas adsorption equilibria and kinetics (self-diffusivities) of CH4 and N2 on pelletized 4A zeolite. The experiment was carried out isothermally without disturbing the adsorbed phase. CH4 was selectively adsorbed over N2 by the zeolite because of its higher polarizability. The multi-site Langmuir model described the pure gas and binary adsorption equilibria fairly well at three different temperatures. The selectivity of adsorption of CH4 over N2 increased with increasing pressure at constant gas phase composition and temperature. This curious behavior was caused by the differences in the sizes of the adsorbates. The diffusion of CH4 and N2 into the zeolite was an activated process and the Fickian diffusion model described the uptake of both pure gases and their mixtures. The self-diffusivity of N2 was an order of magnitude larger than that for CH4. The pure gas self-diffusivities for both components were constants over a large range of surface coverages (0 〈 θ 〈 0.5). The self-diffusivities of CH4 and N2 from their binary mixtures were not affected by the presence of each other, compared to their pure gas self-diffusivities at identical surface coverages.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008917308002
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  • 22
    Digitale Medien
    Digitale Medien
    Impedance Spectroscopic Measurements of Pure Gas Adsorption Equilibria on Zeolites (1999)
    Springer
    Adsorption 5 (1999), S. 159-167 
    Details
    ISSN: 1572-8757
    Schlagwort(e): impedance spectroscopy ; uptake curve ; adsorption ; polarization of adsorbate ; dielectric properties of adsorbed phases
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract Physisorption equilibria of gases on inert porous solids like activated carbon or molecular sieves can be characterized by measuring the (frequency dependent) capacitance of a capacitor filled with a sample adsorbent. This quantity strongly depends not only on the physico-chemical structure of the empty adsorbent in vacuum, but also on the permanent or induced dipole moments of the molecules adsorbed and of the fluid phase. Consequently, it should be possible to determine the excess mass being adsorbed on the internal surface of a highly porous solid by measurements of the dielectric constant. The aim of this work is to show for various pure gases and adsorbents that the change of the capacitance of an adsorption system depends on the adsorbed mass. Therefore, this effect can be used to characterize porous solids and their adsorbates and, for example, to check the state or the quality of industrial adsorbents during a process on site if calibration measurements have been taken (Staudt et al., 1994, 1998).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008969308910
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  • 23
    Digitale Medien
    Digitale Medien
    Liquid Phase Separation of Polar Hydrocarbons from Light Aromatics Using Zeolites (1999)
    Springer
    Adsorption 5 (1999), S. 399-407 
    Details
    ISSN: 1572-8757
    Schlagwort(e): zeolites ; polar compounds ; adsorption ; adsorption isotherms ; equilibrium ; liquid phase ; breakthrough curves ; acetonitrile ; acrylonitrile ; dioxane ; ZSM-5 ; MCM-22 ; Na-X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Physik , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Abstract The liquid phase removal of low concentrations of polar compounds (acetonitrile, acrylonitrile and dioxane) from toluene by adsorption on zeolites reveals very high selectivity factors. Kinetic selectivity factors as high as 16,100 are observed. The selection of the zeolites (MFI, MWW and FAU type) allowed the study of the effects of varying aluminum content, the presence and absence of acidic centers and varying pore volumes. To assess the relative effectiveness of each adsorbent, both equilibrium and continuous flow, pseudo equilibrium, breakthrough experiments were conducted. The continuous flow experiments were carried out at 25 and 75°C. The zeolites H-ZSM-5, H-MCM-22 and Na-X are highly effective in removing the polar compounds from toluene to a concentration level down to less than 20 ppm (detection limit). The results obtained with the equilibrium batch experiments are confirmed by the continuous flow breakthrough experiments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008916917943
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  • 24
    Digitale Medien
    Digitale Medien
    Gravimetric monitoring of adsorption behavior of tetrakis(methylpyrdiniumyl)porphyrin onto quartz crystal surface using an electrode-separated piezoelectric sensor (1998)
    Springer
    Microchimica acta 128 (1998), S. 229-233 
    Details
    ISSN: 1436-5073
    Schlagwort(e): porphyrin ; adsorption ; quartz ; piezoelectric ; sensor
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The adsorption behavior of 5,10,15,20-tetrakis (4-N-methylpyridiniumyl)-porphyrin (H2TMPyP) from aqueous solutions onto a quartz crystal interface was investigated in situ using an electrode-separated piezoelectric sensor (ESPS). With H2TMPyP adsorbed onto quartz crystal surface of the ESPS, its oscillating frequency decreases linearly with increasing adsorption amount. The adsorption densities obtained in the ESPS method were greater than those determined in a solution depletion method. The influence of surface roughness of quartz crystal and bulk solution properties on the measurement of adsorption density in the ESPS method was discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01243054
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  • 25
    Digitale Medien
    Digitale Medien
    Determination of population pharmacokinetic parameters for amikacin in neonates using mixed-effect models (1998)
    Springer
    European journal of clinical pharmacology 53 (1998), S. 337-341 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Key words Amikacin ; Neonate ; Pharmacokinetics ; NONMEM
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract Objective: The population pharmacokinetics of amikacin, in neonates, was investigated using the nonlinear mixed effects model (NONMEM). Methods: One hundred and six steady-state amikacin serum levels were obtained from 53 black neonates with a mean gestational age of 35.1 weeks and mean age at the start of treatment of 3.1 days. A one-compartment model was used to fit the data. Results: The final models for clearance (CL) and volume of distribution (V) were: where WT = birth weight (kg) and P = 1.28 for girls and 1.0 for boys. Inclusion of other fixed effect parameters in the model did not significantly improve the fit of the data. The inter-individual variability for CL and V were 18% and 13%, respectively. Intra-individual variability was 29%. Mean (95% CI) values of CL, V and half-life were 0.048 (0.045, 0.051) l· h−1· kg−1, 0.434 (0.414, 0.453) l· kg−1 and 6.4 (6.2, 6.6) h respectively. Conclusion: Birth weight was an important determinant of both CL and V and, in this data set, gender was also found to influence CL. Mean population pharmacokinetic values were within the range of those previously derived for other neonatal populations using traditional methods.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002280050389
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  • 26
    Digitale Medien
    Digitale Medien
    Sibutramine pharmacokinetics in young and elderly healthy subjects (1999)
    Springer
    European journal of clinical pharmacology 54 (1999), S. 847-849 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Key words Sibutramine ; Pharmacokinetics ; Age
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract Objective: To investigate the pharmacokinetics of the pharmacologically active metabolites of sibutramine (metabolites 1 and 2) in healthy young and elderly volunteers following a single oral dose of sibutramine. Methods: This was an open, parallel-group study completed by 12 young (six male, six female; mean age 24.0 years) and 12 elderly (six male, six female; mean age 70.3 years) healthy volunteers. Blood samples were taken at intervals up to 48 h post-dose. Plasma concentrations of metabolites were determined using HPLC-MS. Model-independent pharmacokinetic parameters of the two metabolites were compared for the two age groups. Results: The similarity of the plasma profiles of the two desmethyl metabolites showed that despite the possibility of reduced hepatic function due to age, the rate and extent of formation of these was the same in both young and elderly, i.e. sibutramine metabolism was not impaired in elderly subjects. There were also no significant differences in elimination of metabolite 2 between groups, although the elderly group showed a slight trend for a reduction in kel. Conclusions: The pharmacokinetics of the two pharmacologically active metabolites of sibutramine (metabolites 1 and 2) were not significantly different between the young and elderly groups in this study. Based on this information, a similar dosing regimen would be appropriate for both the young and elderly.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002280050565
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  • 27
    Digitale Medien
    Digitale Medien
    Pharmacokinetic and bioequivalence evaluation of two generic formulations of oral artesunate (1998)
    Springer
    European journal of clinical pharmacology 53 (1998), S. 375-376 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Key words Artesunate ; Dihydroartemisinin ; Pharmacokinetics ; Bioequivalence
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002280050397
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  • 28
    Digitale Medien
    Digitale Medien
    Irbesartan does not affect the steady-state pharmacodynamics and pharmacokinetics of warfarin (1999)
    Springer
    European journal of clinical pharmacology 55 (1999), S. 593-598 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Key words Irbesartan ; Warfarin ; Pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract Objectives: To determine whether the initiation or titration of irbesartan alters the pharmacodynamics and/or pharmacokinetics of warfarin in a clinically significant manner, thereby requiring additional monitoring of the anticoagulant effect of warfarin. Methods: Daily doses of warfarin were administered to 16 healthy males for 21 days (10 mg on day 1 and 2.5–10 mg on days 2–21). Irbesartan (300 mg/day) or placebo was concomitantly administered on days 15–21. The pharmacodynamic parameters prothrombin time (PT) and prothrombin time ratio (PTR) were evaluated throughout the study. Plasma and urine samples were collected before and up to 24 h after administration on days 14, 15 and 21 for the determination of the maximum concentration (Cmax), time to reach Cmax (tmax), the area under the concentration–time curve (AUC) of S-warfarin and the cumulative urinary excretion of warfarin and its metabolites. Pre-dose plasma samples were also collected to determine the Cmin of S-warfarin (days 12, 13, 14 and 21) and irbesartan (days 19, 20 and 21). Results: Analysis of PTR data revealed no significant difference between the group mean PTR values at day 22 and those at day 15 (P=0.699). S-warfarin concentrations in plasma and urine, as well as the urinary concentrations of the metabolites of warfarin, were not affected by concomitant single- or multiple-dose administration of irbesartan. Plasma Cmin concentrations of S-warfarin and irbesartan were also not affected. Conclusions: No clinically important effect of irbesartan on the pharmacodynamics and pharmacokinetics of warfarin are likely to occur during concomitant administration; therefore, neither a dosage adjustment of irbesartan or warfarin nor any additional monitoring of the anticoagulant effect of warfarin is necessary.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002280050678
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  • 29
    Digitale Medien
    Digitale Medien
    Effect of orlistat on blood cyclosporin concentration in an obese heart transplant patient (1999)
    Springer
    European journal of clinical pharmacology 55 (1999), S. 667-669 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Key words Cyclosporin ; Orlistat ; Pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract Objective: We detected markedly decreased cyclosporin blood levels in a heart-transplanted patient after the gastrointestinal lipase inhibitor orlistat was accidentally added to the treatment program to control for his obesity. Therefore, we determined cyclosporin plasma concentration time kinetics with and without orlistat reexposition in this patient. Methods: Plasma concentration time kinetics of whole blood cyclosporin levels in an obese heart-transplant patient were measured using a standard monoclonal fluorescence polarisation immunoassay. Results were obtained in hourly intervals up to 12 h without and with co-therapy of 3 × 120 mg orlistat (Xenical, Roche Ltd., Switzerland). The orlistat re-exposition was started the day before taking blood samples. Results: Cyclosporin trough levels (98 ng/ml vs 52 ng/ml), maximum concentrations (532 ng/ml vs 74 ng/ml) and the area under the blood drug concentration-time curve (2832 ng h ml−1 vs 700 ng h ml−1) were greatly reduced with orlistat. Conclusions: Orlistat markedly decreased blood cyclosporin concentrations, possibly due to an interference with its absorption in the small intestine. To avoid potential dangerous under-immunosuppression, orlistat should not be used in patients taking cyclosporin.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002280050690
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  • 30
    Digitale Medien
    Digitale Medien
    Pharmacokinetics and pharmacodynamics of candesartan cilexetil in patients with normal to severely impaired renal function (1999)
    Springer
    European journal of clinical pharmacology 54 (1999), S. 953-958 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Key words AT1 receptor antagonist ; Blood pressure ; Candesartan cilexetil ; Candesartan ; Pharmacokinetics ; Renin angiotensin system
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract Objective: We studied the pharmacokinetics and pharmacodynamics of single and multiple doses of candesartan cilexetil 8 mg per day in hypertensive patients with different degrees of renal function impairment. Candesartan is an angiotensin II subtype 1 (AT1) receptor antagonist that is administered orally as candesartan cilexetil which is converted in the active compound. Methods: Twenty-three patients were included, divided into groups according to creatinine clearance (cr cl. group A 〉60 nl · min−1 · 1.73 m−2, group B 30–60 ml · min−1 · 1.73 m−2 and group C 15–30 ml · min−1 · 1.73 m−2). Results: Trough serum concentrations of candesartan were higher in group C compared with group A. The values did not increase after multiple dosing, indicating absence of accumulation. There was a significant negative correlation between the area under the concentration-time curve extrapolated to time infinity (AUCinf) and the glomerular filtration rate (GFR) indicating a lower renal clearance of candesartan in patients with impaired renal function. The onset of haemodynamic and hormonal effects was gradual. During the single-dose study blood pressure as well as plasma renin activity (PRA) and angiotensin II were unchanged at peak. At day 5 of the multiple-dose study blood pressure was lower and both PRA and angiotensin II were higher compared with baseline. Conclusion: Although serum trough levels increased during repeated administration and half-life was higher in patients with impaired renal function, candesartan cilexetil at a dose of 8 mg per day does not lead to drug accumulation in these patients. This dose is effective in lowering blood pressure and appears to be suitable for patients with renal function impairment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002280050581
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  • 31
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of a novel 5-lipoxygenase inhibitor (ABT-761) in pediatric patients with asthma (1998)
    Springer
    European journal of clinical pharmacology 54 (1998), S. 715-719 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Key words ABT-761 ; Pharmacokinetics ; Asthma
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract Objective: The pharmacokinetics of an N-hydroxyurea analog, ABT-761 in asthmatic pediatric patients with asthma were investigated. Methods: A total of 24 patients were enrolled into this 8-day single- and multiple-dose study. Patients received daily doses of ABT-761 according to their body weight: patients of 20–38 kg received 50 mg; patients 〉38 kg but ≤55 kg received 100 mg, and patients ≥55 kg received 150 mg. Results: The mean values for the terminal phase t1/2 were 16–17 h after multiple-dose administration. When normalized for body weight, the mean day 8 Clf values for 50-, 100-mg, and 150-mg doses were 0.57 (n = 13), 0.51 (n = 10), and 0.43 (n = 1) ml · min−1 · kg−1, respectively, while the mean Vz/f values ranged from 0.75 to 0.77 l · kg−1. The mean accumulation ratio observed (day 8 to day 1 AUC0–24 ratio) of ABT-761 was approximately 1.7, which is consistent with the t1/2 of this drug. Body weight, age, and body surface area were virtually identical in explaining the variability in dose-normalized Cmax and AUC values (R 2 = 0.61–0.68). The percents of variance explained by these three variables were within a range of 3% for each pharmacokinetic parameter. Conclusions: The pharmacokinetics of ABT-761 in children were similar to those previously reported in adults. Body weight, age, or body surface area can be used to provide dosing adjustment for ABT-761 in pediatric patients.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002280050540
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  • 32
    Digitale Medien
    Digitale Medien
    Can oral contraceptive steroids influence the elimination of nifedipine and its primary pryidine metabolite in humans? (1998)
    Springer
    European journal of clinical pharmacology 54 (1998), S. 729-734 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Key words Oral contraceptives ; Nifedipine ; Pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract Objective: To investigate the influence of oral contraceptives on cytochrome P450 3A4 (P450NF) activity. Methods: In 23 healthy women, the pharmacokinetics of nifedipine and its main metabolite dehydronifedipine in plasma were assessed after a single oral dose, prior to and after intake of one of two oral contraceptive formulations, one containing 2 mg dienogest and 0.03 mg ethinylestradiol (group A) and the other containing 0.125 mg levonorgestrel and 0.03 mg ethinylestradiol (group B). Results: While the intake of two oral contraceptives for 21 days did not influence the plasma concentration-time curve of unchanged nifedipine, mean AUC0–23.5 h and the mean Cmax values of dehydronifedipine were significantly lower in both groups tested/(24% in group A and 25% in group B). This observation may indicate a reduced formation rate of metabolites and reflects an inhibition of cytochrome P450 3A4 activity. The activation of the same or other metabolic degradation mechanism(s) could explain this result. Conclusion: The investigation presented demonstrates the importance of metabolite measurement when in vivo studies are undertaken to investigate different influences on drug metabolizing ability.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002280050543
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  • 33
    Digitale Medien
    Digitale Medien
    Pharmacokinetics and safety of propiverine in patients with fatty liver disease (1998)
    Springer
    European journal of clinical pharmacology 54 (1998), S. 767-771 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Key words Propiverine ; Fatty liver disease ; Pharmacokinetics ; Adverse effects
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract Objective: The present study was designed to assess the pharmacokinetics of propiverine after single and multiple dosing in patients with and without fatty liver disease. Methods: The serum concentration-time curves of propiverine and its main metabolite propiverine-N-oxide were investigated in 12 patients with mild to moderate impairment of liver function (mean antipyrine clearance 26.0 ml · min−1) and in 12 controls (antipyrine clearance 42.8 ml · min−1). Subjects were treated orally with propiverine hydrochloride (Mictonorm) for 5 days (15 mg t. i. d.) to reach steady state. Results: No significant differences were observed for propiverine and its main metabolite with regard to peak serum concentration (Cmax), area under the serum concentration-time curve (AUC) and elimination half-life (t1/2). Adverse events were reported by 12 patients. Five patients with fatty liver disease and seven patients with normal liver function complained of dry mouth and/or blurred vision. All adverse events reported were transient and mild. Conclusion: No pharmacokinetic differences relevant for safety were observed, comparing patients with and without fatty liver disease following repeated oral administration of propiverine. Thus there seems to be no need to adjust the dose in patients with mild to moderate impairment of liver function.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002280050549
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  • 34
    Digitale Medien
    Digitale Medien
    Limited-sampling strategy models for estimating the area under the plasma concentration–time curve for amlodipine (1999)
    Springer
    European journal of clinical pharmacology 55 (1999), S. 651-657 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Key words Amlodipine ; Limited-sampling models ; Pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract Objective: Develop and validate limited-sampling strategy (LSS) models for estimating the area under the plasma concentration versus time curve (AUC) of amlodipine, using data from a bioequivalence study. Methods: Sixteen healthy volunteers received single 5-mg oral doses of amlodipine, as reference or test formulation, at a 14-day interval, in a randomized, crossover protocol. Plasma concentrations of amlodipine (n = 288), measured by mass spectrometry, were used to develop LSS models. Results: Linear regression analysis of the AUC0–72 and a “jack-knife” validation procedure revealed that LSS models based on two sampling times (12 h and 48 h) predict accurately (R2 = 0.99; bias〈0.01%; precision = 0.03%) the AUC0–72 of amlodipine for each formulation. Validation tests indicate that the 2-point LSS model developed for the reference formulation predicts accurately (R2〉0.90): (a) the individual AUC0–72 for the test formulation in the same group of volunteers; (b) the individual AUC0–72 for the same reference formulation in another bioequivalence study in Brazilian volunteers; (c) the average AUC0–72 reported in seven additional international studies performed under protocols similar to the present investigation; (d) the individual AUC0–72 corresponding to concentration data points provided by a first-order compartmental pharmacokinetic model, when the relative values of either the absorption rate (K abs) or the bioavailability (F) model parameters were set at 0.85 or 0.6, of their respective original values. Conclusions: The 2-point LSS models developed in the current study predict accurately the AUC of amlodipine under a variety of experimental conditions and, thus, may be valuable for exploring the relationships between the pharmacokinetics and pharmacodynamics of this calcium antagonist, at reduced costs of sample acquisition and analysis, and avoiding sampling at “unsociable” hours.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002280050688
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  • 35
    Digitale Medien
    Digitale Medien
    Bioavailability of intranasal formulations of dihydroergotamine (1999)
    Springer
    European journal of clinical pharmacology 55 (1999), S. 677-680 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Key words Dihydroergotamine ; Absorption ; Intranasal ; Randomly methylated β-cyclodextrin (RAMEB) ; Pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract Objective: A comparison of the pharmacokinetic properties of two novel intranasal preparations of dihydroergotamine mesilate (DHEM) with a commercially available intranasal preparation. Methods: Two intranasal formulations of DHEM in combination with randomly methylated β-cyclodextrin (RAMEB) were prepared. Subsequently, in an open, randomised, crossover study in nine healthy volunteers, the following medication was administered: 2 mg DHEM/2% RAMEB nasal spray ( =two puffs of 100 μl); 2 mg DHEM/4 mg RAMEB nasal powder; 2 mg Diergo nasal spray ( =four puffs of 125 μl); 0.5 mg DHEM i.m., and 2 mg DHEM solution p.o. Results: No statistically significant differences were found in maximum plasma concentration (Cmax), time to reach Cmax (tmax), area under plasma concentration–time curve (AUC0–8 h), Frel(t=8 h) and Cmax/ AUC(t=8 h) for the three intranasal preparations. The relative bioavailabilities of the DHEM/RAMEB nasal spray, the DHEM/RAMEB nasal powder and the commercially available DHEM nasal spray were 25%, 19% and 21%, respectively, in comparison with i.m. administration. The relative bioavailability after oral administration was 8%. Conclusion: The pharmacokinetic properties of the novel intranasal preparations are not significantly different from the commercially available nasal spray. Advantages of the DHEM/RAMEB nasal spray are (1) less complicated handling, (2) reduction of the number of puffs and (3) a preference by the volunteers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002280050692
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  • 36
    Digitale Medien
    Digitale Medien
    Influence of the cytochrome P4502D6*4 allele on the pharmacokinetics of controlled-release metoprolol (1998)
    Springer
    European journal of clinical pharmacology 54 (1998), S. 469-474 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Key words CYP2D6 ; Genetic polymorphism ; Metoprolol ; Pharmacokinetics ; Human
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract Aim: The aim of the present paper was to compare the pharmacokinetics of metoprolol in homozygous Caucasian volunteers for the wild-type CYP2D6 allele (CYP2D6*1/CYP2D6*1) and heterozygous (CYP2D6*1/CYP2D6*4) Caucasians. Methods: Thirty-six unrelated healthy male Caucasians were screened for two of the most frequently occurring mutant alleles (CYP2D6*3 and CYP2D6*4) using polymerase chain reaction (PCR). Twenty-four volunteers with a genotype suggesting a rapid hydroxylator phenotype were enrolled in a bioequivalence trial and each received in a randomized, cross-over fashion one of the three formulations compared. Each formulation contained 200 mg metoprolol tartrate/(tablet). In each of the three periods of the trial, one of the formulations was administered under fasting conditions in the morning on 4 consecutive days. Blood for quantification of metoprolol was drawn immediately before the last dose and in selected time intervals thereafter. A sensitive and specific high-performance liquid chromatography (HPLC) method with fluorescence detection was applied for the quantification of metoprolol. Pharmacokinetic parameters were determined for each subject and statistically compared in two groups of 16 homozygous (CYP2D6*1/CYP2D6*1) and six heterozygous (CYP2D6*1/CYP2D6*4) volunteers. Results: Significant differences between homozygous and heterozygous individuals were observed for all pharmacokinetic parameters. The AUC in the course of one those interval of 24 h (AUCτ), minium steady-state concentration (Cmin ss) and average steady-state concentration (Cav ss) values for heterozygous individuals were more than twice those of individuals. Significantly higher values for Css max , t1/2, half-value duration (HVD) and mean residence time (MRT) were also observed in heterozygous volunteers. The higher concentrations of metoprolol in heterozygous individuals also had pharmacodynamic consequences, namely, greater heart rate and blood pressure reduction.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002280050495
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  • 37
    Digitale Medien
    Digitale Medien
    Distribution and metabolism of N G-nitro-l-arginine methyl ester in patients with septic shock (1998)
    Springer
    European journal of clinical pharmacology 54 (1998), S. 627-631 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Key wordsl-NAME ; Pharmacokinetics ; Septic shock
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract Objective: The pharmacokinetics of N G-nitro-l-arginine methyl ester (l-NAME), an inhibitor of nitric oxide (NO) synthesis, was investigated in patients with septic shock. Methods: Blood was sampled at intervals before, during and after 12-h infusion of l-NAME 1 mg · kg−1 · h−1 in nine septic shock patients for determination of plasma concentrations by high-performance liquid chromatography (HPLC). In three patients the renal clearance of the drug was determined. Results: Incubation of l-NAME with plasma and blood in vitro revealed hydrolysis to N G-nitro-l-arginine (l-NOARG), the active inhibitor of NO synthesis. l-NOARG did not undergo further degradation. Continuous intravenous infusion of 1 mg · kg−1 · h−1 of l-NAME for 12 h in patients with septic shock increased blood pressure and resulted in increasing plasma concentrations of l-NOARG (Cmax 6.2 μg · ml−1 at 12 h) whereas l-NAME concentrations reached a plateau within 1.5 h (Cmax 1.0 μg · ml−1). After the infusion was stopped l-NAME disappeared from the plasma rapidly (half-life 19.2 min) whereas l-NOARG concentration declined slowly (half-life 22.9 h). The calculated volume of distribution for l-NAME was 0.45 l · kg−1 body weight and 1.96 l · kg−1 for l-NOARG. The renal clearance for l-NOARG was 3.5% of total body clearance for l-NOARG, whereas l-NAME could not be detected in urine. Conclusion: We conclude that vasoconstriction with l-NAME in septic patients may result from hydrolysis to l-NOARG, the active inhibitor of NO synthesis. The long plasma half-life and large volume of distribution for l-NOARG suggests extensive distribution to extravascular tissues. Since renal excretion is minimal, elimination of the metabolite l-NOARG follows other pathways.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002280050525
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  • 38
    Digitale Medien
    Digitale Medien
    Estimation of the area under the concentration-versus-time curve of carboplatin following irinotecan using a limited sampling model (1998)
    Springer
    European journal of clinical pharmacology 54 (1998), S. 725-727 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Key words Carboplatin ; Irinotecan ; Limited sampling model ; Pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract Objectives: The aim of this study was to develop limited sampling models for estimating the area under the concentration-versus-time curve (AUC) of carboplatin. Methods: Based on pharmacokinetic analyses of 14 patients who received 300 mg · m2 of carboplatin over a 90-min infusion following irinotecan, we developed limited sampling models with stepwise multiple linear regression analysis. We validated these models to be unbiased and precise using pharmacokinetic data of a second group of 14 patients. We also compared the observed and the predicted AUC in the patients using Calvert's formula with the patients' renal function. Results: We developed the following models: AUC (mg · ml−1 · min) = 0.784 × C4 + 1.30 (r 2 = 0.930) and AUC = 0.100 × C0.25 + 0.597 × C4 + 0.140 (r 2 = 0.992), where C0.25 and C4 denote unbound plasma concentrations (μg · ml−1) of carboplatin at 0.25 h and 4 h after the end of infusion, respectively. These models were validated to be unbiased and precise: a mean prediction error (MPE) with standard deviation (SD) = 2.41 (9.45)% and a root mean squared error (RMSE) = 9.42% for the one-sample model, and MPE with (SD) = 1.22 (5.56)% and RMSE = 5.49% for the two-sample model. We also calculated predicted AUC in the patients using Calvert's formula: MPE with (SD) =−5.87 (21.5)% and RMSE = 21.5%. Conclusions: These estimations were, as expected, more accurate than the prediction using Calvert's formula based on patients' renal function. The result of this study confirmed the idea that the pharmacokinetic parameters derived from limited sampling models would be more suitable for pharmacokinetic analysis of carboplatin than those obtained using Calvert's formula.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002280050542
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  • 39
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of oxypolygelatine in healthy volunteers (1999)
    Springer
    European journal of clinical pharmacology 55 (1999), S. 49-51 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Key words Oxypolygelatine ; Pharmacokinetics ; Healthy volunteers ; Tolerability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract Objective/methods: The pharmacokinetics of the plasma substitute oxypolygelatine (OPG) were studied in 12 healthy volunteers after single-dose administration of 27 ml · kg−1 body weight, with a maximum of 2000 ml. OPG was determined in plasma and urine over 48 h after the infusion. Peak plasma OPG concentrations at the end of the infusion were determined to 4.600 (623) μg · ml−1, the area under the plasma concentration/time curve (AUC0∞) was calculated to 70.135 (15.861) μg · h · ml−1. Results: The model-independently calculated volume of distribution came to 23.1 (4.8) l with a clearance total is (Cltot) of 24.6 (6.8) ml · min−1. The initial half-life according to a three-compartment model came to 0.3 (0.2) h, followed by a distribution half-life of 3.1 (2.6) h and a terminal elimination half-life of 13.4 (2.2) h. Cumulative urinary excretion of OPG was 64% after 48 h. Conclusion: This low recovery rate may be explained by the distribution of OPG into the extravascular space and subsequent degradation in tissue sites.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002280050591
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  • 40
    Digitale Medien
    Digitale Medien
    Absence of interaction between erythromycin and a single dose of clozapine (1999)
    Springer
    European journal of clinical pharmacology 55 (1999), S. 221-226 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Key words Clozapine ; Erythromycin ; CYP3A4 ; Pharmacokinetics ; Drug interaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract Objective: To study the suggested pharmacokinetic interaction between erythromycin, a strong inhibitor of CYP3A4, and clozapine. Methods: Twelve healthy male volunteers received a single dose of 12.5 mg of clozapine alone or in combination with a daily dose of 1500 mg erythromycin in a randomised crossover study. Clozapine and its metabolites clozapine-N-oxide and desmethyl-clozapine were measured in serum samples which were collected during a 48 h period and in a sample of the urine secreted over the interval 0–12 h. Results: There were no significant differences in mean area under the serum concentration time curves (1348 (633) nmol h · 1−1 in the control phase and 1180 (659) nmol h · 1−1 in the erythromycin phase), terminal half-lives (19 (13) h and 15 (6) h, respectively), peak serum concentrations (92 (53) nmol · 1−1 and 77 (40) nmol · 1−1, respectively), time to peak serum concentrations (1.4 (0.7) h and 1.5 (1.0) h, respectively) or apparent oral clearances of clozapine (34 (15) l · h−1 and 46 (37) l · h−1, respectively). There were no significant differences in partial metabolic clearances to clozapine-N-oxide (5.1 (3.6) l · h−1 and 7.8 (9.4) l · h−1, respectively) or to desmethyl-clozapine (1.5 (1.3) l · h−1 and 1.8 (1.7) l · h−1, respectively) or in renal clearances of clozapine (0.8 (0.5) l · h−1 and 1.0 (0.7) l · h−1, respectively) between the two phases. Conclusion: These results demonstrate that erythromycin at a clinically relevant dosage does not inhibit the metabolism of clozapine. Hence, CYP3A4 seems to be of minor importance in the disposition of clozapine in humans at least when clozapine is taken at a low single dose.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002280050621
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  • 41
    Digitale Medien
    Digitale Medien
    Lack of influence of menstrual cycle and premenstrual syndrome diagnosis on pregnanolone pharmacokinetics (1999)
    Springer
    European journal of clinical pharmacology 55 (1999), S. 125-130 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Key words Pregnanolone ; Pharmacokinetics ; Premenstrual syndrome
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract Objective: Pregnanolone is a 3α-hydroxylated-5β-reduced metabolite of the female sex steroid hormone progesterone. The compound is currently being evaluated for anaesthetic purposes. Previous studies have indicated a differential physiological response across the menstrual cycle and a different response in patients with premenstrual syndrome (PMS). This study was undertaken to determine whether hormonal changes during the menstrual cycle influence pregnanolone pharmacokinetics and to compare PMS diagnosis-related differences in pregnanolone pharmacokinetics. Methods: Seven patients with premenstrual syndrome and seven female controls were given three increasing doses of pregnanolone in the follicular and luteal phase of the menstrual cycle. Results: Mean pregnanolone elimination half-life varied between 28.4 min and 31.8 min and clearance between 59.6 ml · min−1 · kg−1 and 64.0 ml · min−1 · kg−1, depending on diagnostic group and cycle phase. No significant differences in pregnanolone pharmacokinetic properties were found between PMS patients and controls in either phase of the menstrual cycle. Furthermore, no differences in pharmacokinetic variables were detected between cycle phases. Conclusion: Pregnanolone pharmacokinetics do not differ between follicular and luteal phase of the menstrual cycle, nor between PMS patients and control subjects.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002280050606
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  • 42
    Digitale Medien
    Digitale Medien
    Development of a general method of limited sampling for the determination of AUC for a drug that displays two-compartment pharmacokinetics (1999)
    Springer
    European journal of clinical pharmacology 55 (1999), S. 213-219 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Key words Limited sampling ; Area under the curve ; Pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract Objectives: To develop a method of limited sampling that would enable accurate estimation of the area under the concentration time curve (AUC) when using the log trapezoidal method. Methods: A series of datasets were simulated. Each dataset comprised 1000 subjects. Each subject was “administered” an intravenous bolus dose of a drug that displays two compartment pharmacokinetics. In the first series of simulations, a variety of combinations of the number of sampling times (K) and number of replicate measurements (R) at each of these times were tested, where K × R = 12 (i.e. N = 12). The times that each of the K samples were taken were chosen to be those that divided the AUC into K − 1 trapezoids of equal area. The concentration-time curves were estimated based on a priori estimates of the population parameters. The best combination of K and R was tested under various conditions of parameter variability and assay variability. The combinations were compared with a conventional sampling strategy, where N = 12, K = 12 (R = 1). Results: The combination K = 4 and R = 3 proved to be the “best”. It had similar accuracy to the conventional method. The best limited sampling combination was superior to the conventional method when assay variability was high (CV = 30%), was similar when assay variability was 15%, but the conventional method became statistically superior when assay variability was 7.5% or less. The accuracy of the best limited sampling combination was inversely related to the parameter variability. If K was set to 4 and R allowed to increase to 6 (i.e. N≠ 12), there was no further gain in accuracy. Conclusion: The proposed method of limited sampling is at least as accurate as the conventional intensive sampling technique, but more efficient in terms of sampling.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002280050620
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  • 43
    Digitale Medien
    Digitale Medien
    Renal handling of drugs in the healthy elderly Creatinine clearance underestimates renal function and pharmacokinetics remain virtually unchanged (1999)
    Springer
    European journal of clinical pharmacology 55 (1999), S. 205-211 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Key words Elderly ; Pharmacokinetics ; Renal function
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract Objective: It is commonly assumed that renal function, and in parallel the excretion of drugs, is considerably reduced in the elderly. Endogenous creatinine clearance or indirect estimates of this parameter are generally recommended for adapting drug dosage. The present study evaluates the validity of both assumptions. Methods: We compared pharmacokinetics (and pharmacodynamics) of 50 mg atenolol, 800 mg piracetam and 25 mg hydrochlorothiazide plus 50 mg triamterene in ten healthy young [25 (2) years] and 11 healthy elderly subjects [68 (5) years]. Inulin (Cin) and para-aminohippurate [PAH (CPAH)] clearance (infusion clearance technique), endogenous (CCr) and calculated (Cockroft-Gault) creatinine clearance, analysis of drugs and their metabolites (HPLC), were performed. Renal haemodynamics and the pharmacokinetics of β-adrenergic blocking agent, diuretics and the nootropic agent piracetam, respectively, were measured on separate days. Results: Cin was significantly (P 〈 0.01) lower in the healthy elderly subjects [104 (12) vs 120 (14) ml · min−2 · 1.73 m−2 in the young], but remained within the normal range (〉90 ml · min−2 · 1.73 m−2). In contrast, CCr was even lower in healthy elderly subjects [95 (24) vs 121 (20) ml · min−1 in the young], and the Cockroft-Gault clearance underestimated true glomerular filtration rate (GFR) even more seriously [74 (17) vs 122 (16) ml · min−1]. For atenolol the mean area under the curve (AUC) was similar in both groups [3.16 (0.48) μg · h−1 · ml−1 in the elderly vs 3.01 (0.30) in the young], as was the mean maximal plasma concentration [0.42 (0.07) vs 0.44 (0.06) μg · ml−1], but the proportion of the drug excreted in urine was marginally (P 〈 0.025) lower in the elderly. Similar results were obtained for hydrochlorothiazide, whereas no marked differences between the groups were found for triamterene and its metabolite. Furthermore, the pharmacodynamic action of diuretics was not significantly altered in the elderly. Conclusions: The true GFR of the healthy elderly remains within the normal range and is underestimated by creatinine clearance and more so by its surrogate (Cockroft-Gault clearance). In parallel, pharmacokinetics of renally excreted drugs are not affected in the healthy elderly to a clinically significant extent. For drugs with a narrow therapeutic window, indirect estimates of GFR appear to be an unreliable means for calculating correct dosage in the elderly.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002280050619
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  • 44
    Digitale Medien
    Digitale Medien
    The effect of grapefruit juice on the pharmacokinetics of orally administered verapamil (1998)
    Springer
    European journal of clinical pharmacology 54 (1998), S. 337-340 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Keywords Verapamil ; Grapefruit juice ; Pharmacokinetics ; Hypertension
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract Objective: To investigate the effect of grapefruit juice (GJ) on the pharmacokinetics of orally administered verapamil in hypertensive patients. Methods: Ten hypertensive patients on chronic verapamil treatment participated in a two-day study. On day 1 200 ml of water was given 1 hour before, and together with the morning verapamil dose; on the day 2, water was replaced by GJ in the same order. Serial blood samples were collected and the concentrations of verapamil and its main dealkylated metabolite (D-617) were determined by high-performance liquid chromatography (HPLC). The area under the concentration versus time curve of verapamil (AUCv) and its metabolite D-617 (AUCM) were calculated before and after GJ ingestion. The peak serum concentration (Cmax) and the time until its appearance (tmax) were also determined. Results: GJ did not affect Cmax, tmax, AUCv or AUVm. The AUCv/AUCm ratio (AUCR) was slightly, but significantly, increased after GJ (1.67 vs 1.92). Conclusions: A single administration of GJ with short-acting verapamil has no significant effect on the pharmacokinetics, of verapamil.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002280050470
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  • 45
    Digitale Medien
    Digitale Medien
    Comparative pharmacokinetic study of oral and rectal formulations of artesunic acid in healthy volunteers (1998)
    Springer
    European journal of clinical pharmacology 54 (1998), S. 411-414 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Key words Artesunic acid ; Pharmacokinetics ; Malaria
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract Objective: A single cross-over, comparative pharmacokinetic study of oral and rectal formulations of 200 mg artesunic acid in 12 healthy Malaysian volunteers is reported. Methods: Plasma concentrations of artesunic acid and dihydroartemisinin were determined simultaneously by HPLC with electrochemical detection. The test drug was well tolerated and no undesirable adverse effects were observed. Results: Comparison of pharmacokinetic parameters of artesunic acid after oral and rectal administration showed statistically significant differences in t max and AUC, with no changes for C max and t 1/2. As for dihydroartemisinin, differences were observed for t max and C max but not for AUC. Conclusion: There appear to be pharmacokinetic differences between oral and rectal modes of administration. The significance of these findings should be explored in malaria patients before appropriate therapeutic regimens are devised.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002280050484
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  • 46
    Digitale Medien
    Digitale Medien
    Population pharmacokinetic analysis of pirmenol in healthy volunteers and patients with arrhythmia (1999)
    Springer
    European journal of clinical pharmacology 55 (1999), S. 77-78 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Key words Pirmenol ; Arrhythmia ; Pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002280050596
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  • 47
    Digitale Medien
    Digitale Medien
    Grapefruit juice has no effect on quinine pharmacokinetics (1999)
    Springer
    European journal of clinical pharmacology 55 (1999), S. 393-398 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Key words Grapefruit juice ; Quinine ; Pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract Objective: As quinine is mainly metabolised by human liver CYP3A4 and grapefruit juice inhibits CYP3A4, the effect of grapefruit juice on the pharmacokinetics of quinine following a single oral dose of 600 mg quinine sulphate was investigated. Methods: The study was carried out in ten healthy volunteers using a randomised cross-over design. Subjects were studied on three occasions, with a washout period of 2 weeks. During each period, subjects received a pretreatment of 200 ml orange juice (control), full-strength grapefruit juice or half-strength grapefruit juice twice daily for 5 days. On day 6, the subjects were given a single oral dose of 600 mg quinine sulphate with 200 ml of one of the juices. Plasma and urine samples for measurement of quinine and its major metabolite, 3-hydroxyquinine, were collected over a 48-h period and analysed by means of a high-performance liquid chromatography method. Results: The intake of grapefruit juice did not significantly alter the oral pharmacokinetics of quinine. There were no significant differences among the three treatment periods with regard to pharmacokinetic parameters of quinine, including the peak plasma drug concentration (Cmax), the time to reach Cmax (tmax), the terminal elimination half-life (t1/2), the area under the concentration–time curve and the apparent oral clearance. The pharmacokinetics of the 3-hydroxyquinine metabolite were slightly changed when volunteers received grapefruit juice. The mean Cmax of the metabolite (0.25 ± 0.09 mg l−1, mean ± SD) while subjects received full-strength grapefruit juice was significantly less than during the control period (0.31 ± 0.06 mg l−1, P 〈 0.05) and during the intake of half-strength grapefruit juice (0.31 ± 0.07 mg l−1, P 〈 0.05). Conclusion: These results suggest that there is no significant interaction between the parent compound quinine and grapefruit juice, so it is not necessary to advise patients against ingesting grapefruit juice at the same time that they take quinine. Since quinine is a low clearance drug with a relatively high oral bioavailability, and is primarily metabolised by human liver CYP3A4, the lack of effect of grapefruit juice on quinine pharmacokinetics supports the view that the site of CYP inhibition by grapefruit juice is mainly in the gut.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002280050646
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  • 48
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of oral entacapone after frequent multiple dosing and effects on levodopa disposition (1999)
    Springer
    European journal of clinical pharmacology 55 (1999), S. 461-467 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Key words Entacapone ; Levodopa ; Pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract Objective: Entacapone is a peripherally acting catechol O-methyltransferase (COMT) inhibitor used as an adjunct to each daily levodopa/dopa decarboxylase (DDC) inhibitor dose in the treatment of Parkinson's disease. Parkinsonian patients with advanced disease and motor fluctuations take several doses of levodopa daily, due to the short action of levodopa in this patient population. The present study was conducted in order to evaluate the pharmacokinetics of entacapone after multiple dosing and the pattern of COMT inhibition in erythrocytes during the first day of dosing as well as during steady state. Furthermore, the disposition of plasma levodopa and carbidopa was studied after a single dose of levodopa/carbidopa during the same conditions. Methods: Twelve healthy male volunteers received 200 mg entacapone eight times daily during study day 1 and day 6 at 2-h intervals from 0800 hours to 2200 hours. During days 3, 4 and 5, 200 mg of entacapone was taken ten times daily, from 0800 hours to 0200 hours on the following day. One levodopa/carbidopa tablet (100/25 mg) was taken on study day 1 and day 6 at 1000 hours. Plasma entacapone concentrations and erythrocyte COMT activities were measured frequently on study days 1–2 and 6–7, and twice daily on study days 3–5. Pharmacokinetic parameters calculated from plasma drug concentrations on days 1–2 and 6–7 were compared with each other. Results: There were no differences in maximal plasma concentration (Cmax), time to maximal drug concentration in plasma (tmax), elimination half-life (t1/2) and area under the plasma concentration–time curve (AUC) of entacapone between day 1 and day 6. The mean t1/2 values of entacapone were 1.3 h and 1.8 h during the first and sixth days, respectively; the difference was not significant. No signs of accumulation of entacapone were noted after the first day. Entacapone reduced erythrocyte COMT activity after the first dose, and this effect was quite stable during frequent dosing. There were no indications of accumulation of COMT inhibition during frequent dosing of entacapone. There were no between-day differences in Cmax, t1/2 (2.4 h on days 1–2 and 2.3 h on days 6–7) or AUC of levodopa, whereas tmax occurred at 0.8 h on day 1 and at 1.2 h on day 6 (P = 0.03). There were no between-day differences in the pharmacokinetic parameters (Cmax, tmax and AUC) of carbidopa. Conclusion: Even when dosed frequently, there are neither indications of accumulation of entacapone nor of its COMT inhibiting activity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002280050657
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  • 49
    Digitale Medien
    Digitale Medien
    The effect of short-term dipyrone administration on cyclosporin pharmacokinetics (1999)
    Springer
    European journal of clinical pharmacology 55 (1999), S. 475-478 
    Details
    ISSN: 1432-1041
    Schlagwort(e): Key words Cyclosporin ; Dipyrone ; Pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract Background: A large number of drugs have been shown to affect the metabolism of cyclosporin A (CSA) and, since cyclosporin is characterized by a narrow therapeutic range, the consequences of such drug interactions may often be of clinical importance. Objective: To evaluate the effect of short-term administration of dipyrone on steady state CSA pharmacokinetics. Methods: Six kidney- and two heart-transplanted patients on chronic CSA therapy participated in this study, which consisted of two 4-day study periods separated by 3-week washout periods. The patients received, in addition to their usual drugs, dipyrone 500 mg or placebo t.i.d., as identical-looking tablets, and the order of administration was randomized. CSA concentrations were measured in whole blood by means of radio-immunoassay (CYCLO-Trac SP) daily during the study periods and periodically over 24 h on the fourth study day. Results: CSA concentrations over time were reduced after dipyrone (ANOVA, P 〈 0.01), but statistical significance was noted only at 2, 4, 5 and 10 h after drug intake (P 〈 0.05). Peak CSA concentration was not altered by dipyrone, but the time required to reach maximal concentration was longer with dipyrone treatment than with the placebo (3.8 ± 2.6 h vs 2.1 ± 0.6 h, P 〈 0.05). No consistent changes were noted for CSA trough level, elimination half-life and area under the concentration–time curve from 0 h to 12 h. Separate analysis of the kidney transplanted patients yielded similar results. Conclusions: Short-term administration of dipyrone is associated with a mild decrease in CSA blood concentration, which is most prominent in the first few hours after drug intake. In practice, no dose adjustment of CSA seems to be indicated during a short course of dipyrone treatment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002280050659
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  • 50
    Digitale Medien
    Digitale Medien
    Empirical Relationships Describing Energetics of Adsorption at Low Coverages on Microporous Carbons (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 1011-1020 
    Details
    ISSN: 1572-8943
    Schlagwort(e): adsorption ; adsorption calorimetry ; microporous carbon ; porosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The fundamental empirical relationships that correlate the adsorption energy with physicochemical parameters of adsorbates are discussed. Based on the experimental data of the adsorption enthalpy of different organic adsorbates on microporous activated carbons some new correlations between adsorption enthalpy and entropy at zero surface coverage and physicochemical parameters of adsorbed molecules are proposed. It is shown that they can be applied for the calculation of carbon porosity. The influence of carbon surface oxidation on its energetic heterogeneity is also discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010166708066
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  • 51
    Digitale Medien
    Digitale Medien
    Calorimetric Investigation of the Monolayers Formed At Solid-liquid Interface (1999)
    Springer
    Journal of thermal analysis and calorimetry 57 (1999), S. 643-651 
    Details
    ISSN: 1572-8943
    Schlagwort(e): adsorption ; heat capacity ; solid-liquidinterface ; solid monolayer
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Heat capacity measurements have been made to investigate the formation of two solid monolayers each of n-pentane, n-heptane and n-dodecane adsorbed on graphite, one at submonolayer coverages and the other coexisting with the liquid. At submonolayer coverages the monolayers are found to melt respectively at 99.8, 151.6, and 217.3 K, well below the bulk melting points. The monolayers coexisting with the liquid melted at 205.6 for heptane and at 287.8 K for dodecane, whereas no evidence was obtained for pentane on the formation of such solid monolayer above the bulk melting point. The order persisting in the liquid near the interface depends upon the length of the molecules. The dodecane monolayers showed another transitions below the melting points both at submonolayer and multilayer coverages.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010199522148
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  • 52
    Digitale Medien
    Digitale Medien
    Calorimetric Investigation of Adsorption of Organic Compounds by Active Carbons (1998)
    Springer
    Journal of thermal analysis and calorimetry 54 (1998), S. 333-342 
    Details
    ISSN: 1572-8943
    Schlagwort(e): active carbon ; adsorption ; enthalpies of wetting ; isothermal calorimetry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Enthalpies of wetting of two active carbons and one brown coal coke by several pure liquids (mainly homologous series) were measured at 298.15 K with two quasi-isothermal microcalorimeters. Different measuring cells with cavities of about 0.5 and 15 cm3 were used. The advantage of the larger measuring cell with three independent 15 cm3 cavities is the higher mass of active carbon, leading to a high reproducibility with standard deviations below 1% and a reduced measuring time. Experiments were carried out with n-alkanes, l-alkanols, cycloalkanes and isomers thereof, i.e. 2-propanol, methylcyclohexane, 2,2,4-trimethylpentane (isooctane and 2-ethyl-1-hexanol, and water. Like the polarity, the size and the three-dimensional expansion of the molecules, the energetic and geometric heterogeneity of the adsorbent influences the enthalpy of wetting.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010126631971
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  • 53
    Digitale Medien
    Digitale Medien
    Comparison of Sorptometric and Thermoporometric Measurements on Porous Glass and Some Others (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 323-330 
    Details
    ISSN: 1572-8943
    Schlagwort(e): adsorption ; balance ; gravimetry ; sorption ; thermoporometry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The results of surface structure investigations involving the use of thermoporometry and gas-sorptometry on porous glass, silica and a zeolite were compared. The most frequent and the mean pore width were found to be in accordance, but major differences in specific surface were observed. These two measuring methods complement each other, because with gas adsorption a dry sample is investigated, while with thermoporometry a sample immersed in a liquid is investigated. The probe molecules (nitrogen or noble gas and water or benzene, respectively) differ in size. The features of the two methods are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010194432703
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  • 54
    Digitale Medien
    Digitale Medien
    Derivative Enthalpies of Adsorption of p-Xylene and m-xylene onto NaY and BaY Zeolites at 150°C: Contribution to the prediction of adsorption selectivity (1999)
    Springer
    Journal of thermal analysis and calorimetry 58 (1999), S. 121-128 
    Details
    ISSN: 1572-8943
    Schlagwort(e): adsorption ; calorimetry ; derivative enthalpy ; prediction ; selectivity ; single xylene ; xylene mixture ; zeolite
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The derivative enthalpies of adsorption of m-xylene and p-xylene onto the NaY and BaY zeolites were measured at 150°C, then compared with those obtained at 25°C, and finally used to predict the selectivity of adsorption of xylene mixtures. Significant differences were observed as the temperature was elevated: for the NaY zeolite, the adsorbate-adsorbate interactions became prevalent, in contrast with the BaY zeolite, between zeolite and derivative interactions were stronger. The difference between the adsorption derivative enthalpies of the two xylenes displayed an abrupt variation from 2 molec. α−1 for both zeolites, the filling from which selectivity towards m-xylene for the NaY zeolite and towards p-xylene for the BaY zeolite appeared. The preferentially adsorbed xylene was closely connected with the sense of this difference, which changed with the zeolite.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010191820215
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  • 55
    Digitale Medien
    Digitale Medien
    Thermodynamics of Adsorption on Microporous Fractal Solids (1998)
    Springer
    Journal of thermal analysis and calorimetry 54 (1998), S. 351-361 
    Details
    ISSN: 1572-8943
    Schlagwort(e): active carbon ; adsorption ; adsorption thermodynamics ; fractal dimension ; microporosity ; pore diameter ; potential theory
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A new adsorption isotherm equation based on the extension of the potential theory of adsorption on microporous fractal solids and corresponding thermodynamic functions were formulated and applied for description of the experimental data of adsorption on a microporous carbon. The comparison of the obtained results with the original Dubinin-Astakhov equation is presented. In this paper the dependence of thermodynamic functions (the differential molar enthalpy of adsorption ΔH and the differential molar entropy of adsorption ΔS) on the fractal dimension D are discussed, as well.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010130700112
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  • 56
    Digitale Medien
    Digitale Medien
    Thermogravimetric Analysis of γ-Aminopropyl-trimethoxysilane Adsorbed on Silica Support (1999)
    Springer
    Journal of thermal analysis and calorimetry 58 (1999), S. 67-76 
    Details
    ISSN: 1572-8943
    Schlagwort(e): adsorption ; DRIFT spectroscopy ; elemental analysis ; γ-aminopropyl-trimethoxysilane ; thermogravimetric analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract A comparative method based on thermogravimetry is applied in order to characterise chemically functionalised surfaces. The mass loss of silica modified with γ-aminopropyl-trimethoxysilane (γ-APS) adsorbed from a range of solvents is interpreted by considering the physically adsorbed water, the silanol groups and the organic solvent. DRIFT spectroscopy is used to analyse the binding structure and adsorption mechanism. The mass loss calculated from thermogravimetric analysis is found to be in agreement with the values obtained by classical elemental analysis. Thermogravimetric analysis is found to be a quick and reproducible method, which only requires a few milligram sample. The amount adsorbed seems to be primarily dependent on the solvation of the γ-aminopropyl-trimethoxysilane by the solvent. A good solvent prevents adsorption as shown when comparing the magnitude of the mass loss with the difference between the solubility parameters of the γ-APS and the solvents. Ethanol seems to influence the structure of the adsorbed γ-aminopropyl-trimethoxysilane film.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010195620272
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  • 57
    Digitale Medien
    Digitale Medien
    Sol-Gel Synthesis and Gas Adsorption Properties of CuCl Modified Mesoporous Alumina (1998)
    Springer
    Journal of sol gel science and technology 11 (1998), S. 185-195 
    Details
    ISSN: 1573-4846
    Schlagwort(e): cuprous chloride ; gamma-alumina ; adsorption ; ethylene ; carbon monoxide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Cuprous chloride (CuCl) modified unsupported γ-alumina membranes and adsorbent granules were synthesized by sol-gel processing followed by wet-impregnation of CuCl. The CuCl coated γ-alumina remains mesoporous with a uniform pore size distribution and a large surface area. The mesoporous alumina granules, prepared by a sol-gel oil-drop process, exhibit excellent mechanical strength and attrition resistance. The CuCl modified γ-alumina preferentially adsorbs ethylene and carbon monoxide, with a saturated adsorption capacity of 0.67 and 0.78 mmol/g, respectively. Both equilibrium capacity and kinetic rate for adsorption of ethylene and carbon monoxide on the CuCl modified γ-alumina are much larger than those for ethane and carbon dioxide. These results indicate the potential use of the sol-gel derived CuCl modified γ-alumina for separation of ethylene or carbon monoxide from its gas mixture containing ethane or carbon dioxide.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008601715782
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  • 58
    Digitale Medien
    Digitale Medien
    Computational studies on the diffusion behaviour of alkylaromatics in large pore zeolites (1999)
    Springer
    Topics in catalysis 9 (1999), S. 225-234 
    Details
    ISSN: 1572-9028
    Schlagwort(e): large pore zeolites ; alkylaromatics ; computations ; adsorption ; diffusion characteristics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Alkylation of aromatics over solid acid catalysts such as zeolites, has emerged in the recent past as a viable alternative to conventional Friedel–Crafts alkylation over environmentally hostile catalysts. We studied the diffusion behaviour of ethylbenzene (EB), isobutylbenzene (IBB), o-, m- and p-isobutylethylbenzene (IBEB) in various zeolites such as offretite (OFF), cancrinite (CAN), ZSM-12 (MTW) and ZSM-18 (MEI) by computational procedures. The periodic variations of interaction energy between the molecules and zeolite framework in the calculated diffusion energy profiles are used to predict the energy barrier for diffusion. We analyzed the results to understand the product selectivity in the formation of IBEB in the transalkylation/disproportionation reaction between IBB and EB. The results indicated that the zeolites with channel-like pores are more suitable than those with cage-like pores to achieve better selectivity. The zeolites with channels whose diameters are close to the dimensions of the molecules and those which do not have intersecting channels are better selective catalysts. The efficiency of shape selective production of p-IBEB in these zeolites will be in the order MEI 〈 OFF ∼ MTW 〈 CAN as predicted from their diffusion energy barriers. The detailed analysis of the configurations of the molecules in the most favourable and unfavourable adsorption location, indicate that the p-IBEB has favourable interaction energy in all the four zeolites with different pore architecture, compared to o- and m-IBEB except for MEI. It could be concluded that the pore architecture plays a dominant role in controlling the adsorption and diffusion characteristics of these molecules. The actual values of interaction energy themselves are indication of their adsorption behaviour inside the pores of the zeolite.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019122924817
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  • 59
    Digitale Medien
    Digitale Medien
    A density functional study of Ti/MgCl 2 -supported Ziegler–Natta catalysts (1999)
    Springer
    Topics in catalysis 9 (1999), S. 235-250 
    Details
    ISSN: 1572-9028
    Schlagwort(e): Ziegler–Natta ; density functional theory ; adsorption ; polymerisation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Total energy pseudopotential calculations have been used to examine the adsorption of TiCl4 at both the 110 and 100 surfaces of magnesium chloride. Titanium(IV) chloride is found to bind most strongly on the 100 surface resulting in the formation of a complex with approximately trigonal bipyramidal coordination of titanium, which will dissociate to form TiCl 3 + and Cl− with an energy of 127.7 kJ mol−1. Cluster calculations indicate that this site only weakly binds ethene, but does catalyse the formation of C–C bonds with an activation energy consistent with experimental estimates.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019174908887
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  • 60
    Digitale Medien
    Digitale Medien
    NO adsorption on Pd clusters. A density functional study (1999)
    Springer
    Topics in catalysis 9 (1999), S. 123-133 
    Details
    ISSN: 1572-9028
    Schlagwort(e): NO/Pd ; adsorption ; clusters ; DFT
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The interaction of NO with Pd clusters has been studied by means of the LCGTO-DF method. Metal cluster models (up to 13 atoms) with different size and geometry have been used to describe the atop, bridge and three-fold sites. The use of different model core potentials to increase the size of the cluster model treated and to save computational time has been discussed. The binding energies of N(1s), 4σ, 5σ and 1π electrons are calculated and compared directly to the experimental XPS and UPS data available. The NO is tilted with respect to the surface normal axis when adsorbed on top and bridge sites by about 52.6 and 46.7 degrees, respectively. On the two types of three-fold sites (hcp and fcc) the NO remains upright. The bending angle is very sensitive to the cluster size and affects the binding energies of N(1s), 4σ, 5σ and 1π orbitals. The NO adsorption energies on the different adsorption sites have been estimated using different cluster models. The vibrational frequencies have been calculated in the harmonic approximation and they are in reasonable agreement with the available experimental values. The cluster model approach is discussed in terms of its reliability to determine the adsorption energies and the favored site of adsorption.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019127025726
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  • 61
    Digitale Medien
    Digitale Medien
    Yeasts Reduce the Stimulatory Effect of Acetate Esters from Apple on the Germination of Botrytis cinerea Conidia (1999)
    Springer
    Journal of chemical ecology 25 (1999), S. 1555-1565 
    Details
    ISSN: 1573-1561
    Schlagwort(e): Yeasts ; Botrytis cinerea ; apple ; volatiles ; gray mold ; biological control ; fungal interaction ; acetate esters
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract The fungus, Botrytis cinerea, causes decay in apples in postharvest storage. Conidia of B. cinerea on polycarbonate membranes were incubated on filter paper disks saturated with water or suspensions of yeasts (2 × 106 CFU/filter) and then exposed for 24 hr at 22°C to 0–16 μl of ethyl, butyl, or hexyl acetates injected into the headspaces of 500-cc glass jars. Germination of conidia was increased by exposure to 4–16 μl of ethyl acetate compared to the no-ester controls. Conidia were stimulated to germinate by 4 μl of butyl acetate and 8 μl of hexyl acetate, but greater volumes were toxic to germination. The yeasts Cryptococcus laurentii and Sporobolomyces roseus were more effective at reducing the stimulatory effect than Saccharomyces cerevisiae. Acetate esters also stimulated germination of conidia on polycarbonate membranes on apples inside jars. Cryptococcus laurentii or S. roseus suppressed this effect more than S. cerevisiae. Germination of conidia on a membrane on water inside a 3.9-liter jar containing an apple was 2.5-fold greater than the no-apple control. Butyl acetate increased Botrytis infection of apple wounds. Butyl and hexyl acetate were detected by GLC in the headspace of Golden Delicious apples. Results indicated that some acetate esters produced by apple stimulated germination of B. cinerea conidia, and this effect was suppressed by yeasts.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1020884715616
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  • 62
    Digitale Medien
    Digitale Medien
    Characterization of Porous Carbonaceous Sorbents Using High Pressure CO2 Adsorption Data (1998)
    Springer
    Journal of porous materials 5 (1998), S. 275-287 
    Details
    ISSN: 1573-4854
    Schlagwort(e): activated carbons ; adsorption ; characterization ; Dubinin-Radushkevich ; carbon dioxide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract In this paper we present adsorption isotherms of carbon dioxide on five different activated carbons from CHEMVIRON CARBON Belgium (Centaur HSV, BPL 410, F30-470, WS 42, Reactivated) and on a carbon molecular sieve from BERGBAU FORSCHUNG Gmbh (CMS II). The temperature is 303 K and the pressure ranges from 100 kPa up to 4000 kPa. Such conditions correspond to relative pressures ranging from 0.01 to 0.5. We also provide, for the same six sorbents, the nitrogen isotherms at 77 K (pressure: 0.001 to 100 kPa, relative pressure: 10-5 to 1). A theoretical treatment based on the Dubinin-Radushkevich and Stoeckli concept is presented and applied to the experimental results in order to obtain the micropore size distribution function (considered as Gaussian) of each sorbent. Using the CO2 data, it is possible to point out important structural differences between the six carbons. The theoretical treatment provides micropore size distribution functions in agreement with what is physically expected. Using N2 data, the structural differences are not so well marked. As a consequence, the structural parameters provided by the theoretical treatment are not reliable: except for the total micropore volume, they fluctuate strongly when changing the relative pressure domain of the used data.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009638406224
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  • 63
    Digitale Medien
    Digitale Medien
    Pilot study in humans on the pharmacokinetics and safety of propofol 6% SAZN (1999)
    Springer
    Pharmacy world & science 21 (1999), S. 239-240 
    Details
    ISSN: 1573-739X
    Schlagwort(e): anaesthesia ; Clinical pharmacology ; Emulsion formulation ; Fat emulsion ; Propofol ; Pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract In a pilot study on the first application of Propofol 6% SAZN in humans, the pharmacokinetics and safety of the new product seem to be similar to those of Propofol 1% SAZN and Diprivan®‐10 after bolus injection. The results will have to be confirmed in a larger clinical study in order to develop Propofol 6% SAZN as an alternative for Diprivan®‐10.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008701004814
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  • 64
    Digitale Medien
    Digitale Medien
    Determination and pharmacokinetics of dextromoramide in methadone maintenance therapy. (1998)
    Springer
    Pharmacy world & science 20 (1998), S. 83-87 
    Details
    ISSN: 1573-739X
    Schlagwort(e): Dextromoramide ; HPLC determination ; Liquid‐liquid extraction ; Methadone ; Methadone maintenance therapy ; Palfium® ; Pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract To study the pharmacokinetics of dextromoramide in long‐term opiate addicts on methadone maintenance therapy (MMT) a reverse‐phase HPLC technique was developed to monitor dextromoramide and methadone concentrations in plasma simultaneously. After liquid‐liquid extraction from plasma, dextromoramide and methadone were determined using a Supelcosil LC‐ABZ column and a mobile phase of KH2phosphate buffer (25 mM, pH 2.5) mixed with acetonitrile (80:20, v/v) and UV detection at 206 nm. The method was found to be sufficiently sensitive, specific and reproducible to apply in six subjects on MMT for many years, receiving orally administered dextromoramide as adjuvant. Pharmacokinetic data sets for dextromoramide in each subject were conducted and analysed further, indicating short elimination half‐life values (71 min, range 31‐152 min). Contrary to previous studies, in all subjects tested the pharmacokinetics of dextromoramide are best described using an one‐compartment model.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008699623190
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  • 65
    Digitale Medien
    Digitale Medien
    Pharmacokinetics of quinine in African patients with acute falciparum malaria. (1998)
    Springer
    Pharmacy world & science 20 (1998), S. 118-122 
    Details
    ISSN: 1573-739X
    Schlagwort(e): Quinine ; Acute falciparum malaria ; Pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The pharmacokinetics of quinine were studied in six Nigerian patients during acute uncomplicated falciparum malaria and convalescent periods. An oral dose of 10 mg/kg quinine dihydrochloride administered 8‐hourly for 7 days gave parasite and fever clearance times of 36.0 ± 16.6 h and 18.0 ± 6.4 h, respectively. From the individual quinine plasma profiles the mean plasma concentration of quinine at the time of parasite clearance was estimated as 4.5 ± 1.1 μg/ml. Plasma quinine levels during malaria rose rapidly reaching a peak around the second and third days and declining thereafter as patients improved clinically. In acute malaria plasma quinine levels were more than two-fold higher than in convalescence; the mean AUC(0-12) in malaria was 37.9 ± 14.7 μg.h/ml compared to 17.9 ± 8.5μg.h/ml in convalescence. The apparent oral clearance (CL/F) and volume of distribution (Vd/F) duri ng the acute phase of the malaria (1.9 ± 0.7 ml/min/kg and 1.8 ± 0.9 l/kg, respectively) were significantly lower than in convalescence (4.5 ± 2.1 ml/min/kg and 4.2 ± 3.2 l/kg). The present data suggest that malaria parasites in African patients are still very sensitive to quinine and that the current dosage of quinine is effective for the treatment of acute falciparum malaria in African patients without augmenting therapy with any other drug such as tetracycline or sulphadoxine-pyrimethamine. It also confirms that malaria significantly alters the pharmacokinetics of quinine in humans.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008699022244
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  • 66
    Digitale Medien
    Digitale Medien
    Mechanisms of drug transfer across the human placenta. (1998)
    Springer
    Pharmacy world & science 20 (1998), S. 139-148 
    Details
    ISSN: 1573-739X
    Schlagwort(e): Human placenta ; Drug transfer ; Drug transport ; Pharmacokinetics ; Placenta perfusion ; Membrane vesicles ; Cotyledon ; Trophoblast ; Cell culture
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract In this review we summarized literature data on the mechanisms of human placental drug transport studied in the isolated perfused placental cotyledon, placental membrane vesicles or trophoblastic cell cultures. Overall human placental drug transport rarely exceeds the transfer of flow‐dependent and membrane‐limited marker compounds. Interestingly, relatively often placental drug transfer appeared to be much smaller, indicating impaired trans-placental transport, depending on the physico-chemical characteristics of the drug or placental factors such as tissue binding or metabolism. Although in perfusion studies overall human placental drug transport occurs by simple diffusion, at the membrane level several drug transport systems have been found, mainly for drugs structurally related to endogenous compounds.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008656928861
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  • 67
    Digitale Medien
    Digitale Medien
    Effect of hepatic insufficiency on pharmacokinetics and drug dosing (1998)
    Springer
    Pharmacy world & science 20 (1998), S. 183-192 
    Details
    ISSN: 1573-739X
    Schlagwort(e): Hepatic disease ; Cirrhosis ; Pharmacokinetics ; Pharmacodynamics ; Dosage adjustment
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The liver plays a central role in the pharmacokinetics of many drugs. Liver dysfunction may not only reduce the plasma clearance of a number of drugs eliminated by biotransformation and/or biliary excretion, but it can also affect plasma protein binding which in turn could influence the processes of distribution and elimination. In addition, reduced liver blood flow in patients with chronic liver disease will decrease the systemic clearance of flow limited (high extraction) drugs and portal‐systemic shunting may substantially reduce their presystemic elimination (first‐pass effect) following oral administration. When selecting a drug and its dosage regimen for a patient with liver disease additional considerations such as altered pharmacodynamics and impaired renal excretion (hepatorenal syndrome) of drugs and metabolites should also be taken into account. Consequently, dosage reduction is necessary for many drugs administered to patients with chronic liver disease such as liver cirrhosis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008656930082
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  • 68
    Digitale Medien
    Digitale Medien
    Pharmacokinetic and pharmacodynamic comparison of two doses of calcium folinate combined with continuous fluorouracil infusion in patients with advanced colorectal cancer (1999)
    Springer
    Pharmacy world & science 21 (1999), S. 184-189 
    Details
    ISSN: 1573-739X
    Schlagwort(e): Chemotherapy ; Colorectal cancer ; Fluorouracil ; Folinate ; Leucovorin ; Pharmacokinetics ; Toxicity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The optimum dose of calcium folinate (leucovorin) as modulator of fluorouracil has not been defined yet. We conducted a randomized trial to compare the pharmacokinetics/pharmacodynamics of two doses of calcium folinate. 16 patients with advanced colorectal cancer were treated with 650 mg/m2/d fluorouracil as 5 day continuous infusion and randomized to receive either 20 mg/m2 or 100 mg/m2 calcium folinate as short infusion twice daily. The two diastereoisomers of calcium folinate were analyzed separately by chiral HPLC to account for differences in their pharmacokinetics. The pharmacokinetics of fluorouracil was not affected by folinate dosing. Total clearance of the active (6S)-diastereoisomer was found to be lower after the higher dose of folinate which can be explained by nonlinear metabolism. The incidence of treatment‐induced mucositis significantly increased with (6S)‐folinate exposure, whereas fluorouracil exposure was not related to this type of toxicity. In conclusion, exposure to folinate is more important for toxicity in this regimen than fluorouracil pharmacokinetics. Therefore, monitoring of fluorouracil plasma levels is not useful in this combination. Our results show that folinate dose should be carefully selected. Lower doses of folinate might be preferred because of less toxicity compared to higher doses.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008671129128
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  • 69
    Digitale Medien
    Digitale Medien
    Clinical pharmacokinetics of antimicrobial drugs in cystic fibrosis. (1998)
    Springer
    Pharmacy world & science 20 (1998), S. 149-160 
    Details
    ISSN: 1573-739X
    Schlagwort(e): Antibiotics ; Cystic Fibrosis ; Pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The disposition of many drugs in cystic fibrosis is abnormal compared with healthy individuals. In general, changes include an increased volume of distribution expressed in liters per kg bodyweight for highly hydrophilic drugs such as aminoglycosides, and, to a lesser extent, for penicillins and cephalosporins, together with an increased total body clearance. The main reason for the increased volume of distribution is the increased amount of lean tissue per kg bodyweight, since patients with CF are generally undernourished and have a paucity of adipose tissue. The reason for the increased renal clearance is less clear. Increased glomerular filtration and tubular secretion have been observed. Protein binding generally is unaltered in CF. The fluorquinolones and vancomycin show no altered pharmacokinetics in CF although gastro-intestinal absorption may be delayed for fluorquinolones. Sulphamethoxazole shows increased clearance due to an increased acetylation and, in the case of trimethoprim, renal clearance is increased compared with healthy individuals. As a consequence, drugs that show increased clearance, will lead to reduced serum concentrations and smaller AUCs and therefore CF patients require larger doses per kg bodyweight.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008634911114
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  • 70
    Digitale Medien
    Digitale Medien
    Complexation of Gold(III)-Chloride at the Surface of Hematite (1998)
    Springer
    Aquatic geochemistry 4 (1998), S. 215-231 
    Details
    ISSN: 1573-1421
    Schlagwort(e): Gold ; hematite surface ; surface complexation ; adsorption ; potentiometric titration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract The acid/base properties of the hematite/water interface and surfacecomplexation with gold has been studied by potentiometric titrations in thefour component system H+ – ≡FeOH –AuCl 4 - – Cl-. Equilibrium measurementswere performed in NaCl media at 298.2 K. In the evaluation of equilibriummodel from experimental data the constant capacitance model was applied. Theacid/base properties were investigated in 0.1 M NaCl in the range 2.6 ≤pH ≤ 7.4. The resulting intrinsic constants for protonation anddeprotonation of hydroxyl groups at the surface were logβ 1,1,0,0(int) s = 7.10 ± 0.06 andlog β -1,1,0,0(int) s = - 7.80 ±0.06. The density of proton active surface sites was 2.85nm-2 and the specific capacitance 2.5 C V-1 m-2. In the investigation of surface complexation of gold, thepotentiometric titrations were performed in the range 2.0 ≤ pH ≤ 10.2.Titration data was supplemented with analysis of Au in the aqueous phase byatomic absorbance spectrometry. The equilibrium model proposed consists ofthe following monodentate surface complexes: ≡FeOHAuCl3(log β 0,1,1,-1 s = 1.45 ± 0.03),≡FeOHAuCl2OH (logβ -1,1,1,-2 s = -3.89 ± 0.02), ≡FeOHAu(OH)3 (logβ -3,1,1,-4 s = -21.94 ± 0.05). Aslightly better fit could be obtained by assuming formation of a bidentatecomplex with the composition(≡FeO)2Au(OH)H2O. However, based onstructural arguments this complex was rejected.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009622915376
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  • 71
    Digitale Medien
    Digitale Medien
    Structure and molecular motion of poly(ethylene oxide) chains adsorbed on a silica-tethered poly(methyl methacrylate) by the spin label method (1998)
    Springer
    Colloid & polymer science 276 (1998), S. 412-419 
    Details
    ISSN: 1435-1536
    Schlagwort(e): Key words poly(ethylene oxide) ; silica-tethered poly(methyl methacrylate) ; adsorption ; spin-label ; molecular motion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract  The spin-label method was used to study the structure and molecular motion of poly(ethylene oxide) (PEO) chains adsorbed on a silica-tethered poly(methyl methacrylate) (PMMA). Spin-labelled PEO with a narrow molecular weight distribution, having number averaged molecular weight (M N)=6.0×103, was adsorbed on the surface of the silica-tethered PMMA with various grafting ratios in carbon tetrachloride solution at 35 °C. ESR spectra were measured at various temperatures after the samples were completely dried. The ESR spectra are composed of two spectra arising from spin-labels attached to “train” and “tail” segments, which are strongly and weakly interacted with the silica surface, respectively. The fractional amount of the “tail” segments increases extremely with the grafting ratio of PMMA. Molecular mobility of the PEO chains estimated from the temperature dependence of the ESR spectra also decreases significantly with the grafting ratio of PMMA. Structure and molecular motion of the PMMA chains tethered on the silica were also studied using the spin-labelled PMMA. Consequently, parts of the PEO segments penetrate into the PMMA chains and is adsorbed on the silica surface (“train” segments), whereas parts of the PMMA segments protrude from the surface. The other PEO segments are entangled with the tethered PMMA chains (“tail” segments).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s003960050260
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  • 72
    Digitale Medien
    Digitale Medien
    Sulfur isotope values in a forested catchment over four years: Evidence for oxidation and reduction processes (1999)
    Springer
    Biogeochemistry 44 (1999), S. 51-71 
    Details
    ISSN: 1573-515X
    Schlagwort(e): adsorption ; bacterial dissimilatory sulfate reduction ; dry deposition ; forested catchment ; Lake Gårdsjön ; isotopes ; oxidation of sulfur ; sulfate ; sulfur ; Sweden
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract A small catchment on the Swedish West Coast has been studied over four years to determine S dynamics by using S isotope ratios. A Norway spruce dominated forest covers the catchment, and small peat areas occur in the lower parts of the catchment. The runoff δ34SSO4 values varied both during the year, and from year to year. Over the period from February 1990 to December 1993, the δ34SSO4 values ranged from −1‰ to +11‰. Over the same period, the throughfall δ34SSO4 values ranged from +1‰ to +15‰. There was no correlation (r2 = 0.01; Pr(F) = 0.57) between δ34SSO4 values in throughfall and runoff. Since the only input of S to the catchment is atmospheric deposition, the long-term runoff S mass flux is controlled by the deposition. Therefore, processes in the catchment are responsible for the variation in the runoff δ34SSO4 values. During periods with 34SSO4 enriched runoff, bacterial dissimilatory SO42- reduction occurs in the catchment. After very dry periods, oxidation of this reduced S, which is 32S-enriched, can be traced in runoff. Previous studies of the catchment have not been able to distinguish between: 1) oxidation of reduced S and dry deposition, and 2) reduction and adsorption. From the current study, it can be concluded that adsorption and dry deposition cannot cause the observed variation in runoff δ34SSO4.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006030008089
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  • 73
    Digitale Medien
    Digitale Medien
    Olfactory Responses of Parasitoid Apoanagyrus lopezi to Odor of Plants, Mealybugs, and Plant–Mealybug Complexes (1998)
    Springer
    Journal of chemical ecology 24 (1998), S. 37-48 
    Details
    ISSN: 1573-1561
    Schlagwort(e): Apoanagyrus lopezi ; Phenacoccus manihoti ; cassava ; biological control ; resistance ; olfactometer ; herbivore-induced synomones ; volatile chemicals
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Apoanagyrus (Epidinocarsis) lopezi De Santis is an endoparasitoid used in the biological control of the cassava mealybug Phenacoccus manihoti Matile-Ferrero in Africa. The response of naive and mated females of A. lopezi to odors from cassava plant (var. Zanaga), parasitized or unparasitized mealybugs, and plant–mealybug host complexes with or without feeding hosts was investigated in a Y-tube olfactometer. Dual-choice tests revealed that mealybug-infested plants and mealybug-damaged plants were the major sources of volatiles that attract female parasitoids to the microhabitat of its hosts. The emission of volatile chemicals appears not to be limited to the infested plant part but to occur systemically throughout the plant. On their own, unparasitized mealybugs were more attractive than uninfested plants or parasitized mealybugs alone. Parasitization of P. manihoti by A. lopezi decreased the response of parasitoids to mealybugs or mealybug–plant complexes. Plants infested with unparasitized hosts attracted more female parasitoids than plants infested with parasitized mealybugs. These results indicate that, in the long-range host-searching process, females of A. lopezi respond mainly to mealybug-induced synomones, and specific host-derived cues play a minor role.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022332711331
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  • 74
    Digitale Medien
    Digitale Medien
    Suppressive Impact of Glucosinolates in Brassica Vegetative Tissues on Root Lesion Nematode Pratylenchus neglectus (1998)
    Springer
    Journal of chemical ecology 24 (1998), S. 67-80 
    Details
    ISSN: 1573-1561
    Schlagwort(e): Brassica ; Pratylenchus neglectus ; nematode ; biological control ; suppression ; glucosinolate ; isothiocyanate ; aliphatic ; 2-phenylethyl ; nematicide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract The potential of tissue amendments from a variety of wild and cultivated Brassica spp. to kill the root lesion nematode (Pratylenchus neglectus) in soil was assessed in laboratory experiments. Soil amended with leaf tissues was highly nematicidal, killing 56.2–95.2% of exposed nematodes. Amendment with root tissues was less effective, causing 0–48.3% mortality. Little of the suppressive impact by leaf tissues could be related to either total contents or any individual glucosinolate as determined by HPLC analysis. While the levels of total glucosinolates within root amendments had a nonsignificant relationship to nematode mortality, levels of 2-phenylethyl glucosinolate within root amendments significantly correlated with nematode suppression (P 〈 0.001). Amendment of soils with equimolar levels of purified 2-phenylethyl isothiocyanate resulted in comparable levels of nematode mortality, suggesting that 2-phenylethyl glucosinolate has a role in the suppressive impact of Brassica spp. root tissues.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022336812240
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  • 75
    Digitale Medien
    Digitale Medien
    Inhibition of Water Fern Salvinia minima by Cattail (Typha domingensis) Extracts and by 2-Chlorophenol and Salicylaldehyde (1998)
    Springer
    Journal of chemical ecology 24 (1998), S. 1483-1490 
    Details
    ISSN: 1573-1561
    Schlagwort(e): Aquatic plant ; bioassay ; biological control ; phenolic compounds ; phytotoxicity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract The allelopathic potential of a cattail species (Typha domingensis) towards the common water fern (Salvinia minima) was studied in a short-term bioassay. Aqueous extracts of cattail plants (roots, stems, and leaves) as well as two of its phenolic compounds (2-chlorophenol and salicylaldehyde) were found to inhibit the growth of Salvinia when incorporated in the growth medium. After a period of seven days, chlorophyll concentration, fresh weight, dry weight, and number of fronds of Salvinia were compared and correlations were found among the different parameters. The results suggest an inhibitory effect by components of Typha, especially of the root fractions. Results from pure chemicals are in qualitative and quantitative agreement with those obtained from the cattail extracts.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1020955615868
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  • 76
    Digitale Medien
    Digitale Medien
    Allelopathic Suppression of Pseudomonas solanacearum Infection of Tomato (Lycopersicon esculentum) in a Tomato-Chinese Chive (Allium tuberosum) Intercropping System (1999)
    Springer
    Journal of chemical ecology 25 (1999), S. 2409-2417 
    Details
    ISSN: 1573-1561
    Schlagwort(e): Allelopathy ; Allium tuberosum ; antibacterial activity ; biological control ; intercropping ; Lycopersicon esculentum Mill ; Pseudomonas solanacearum E. F. Smith ; root exudates ; soil-borne diseases
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Tomato plants were grown alone or intercropped with Chinese chive plants, with or without the inoculation of Pseudomonas solanacearum. Chinese chive plants had no detrimental effects on the growth of tomato plants but significantly delayed and suppressed the occurrence of bacterial wilt of tomato. P. solanacearum population decreased faster in the soil grown with tomato alone than that in the soil grown with both tomato and Chinese chive. However, P. solanacearum population in bare soil was higher than that grown with Chinese chive. Root exudates of Chinese chive collected with a continuously trapping system were inhibitory to multiplication of P. solanacearum.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1020809805081
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  • 77
    Digitale Medien
    Digitale Medien
    The Response of Phytoseiulus persimilis to Spider Mite-Induced Volatiles from Gerbera: Influence of Starvation and Experience (1999)
    Springer
    Journal of chemical ecology 25 (1999), S. 2623-2641 
    Details
    ISSN: 1573-1561
    Schlagwort(e): Herbivore-induced synomones ; infochemicals ; semiochemicals ; learning ; biological control ; prey location ; behavior ; Acarina ; Phytoseiulus persimilis ; Tetranychus urticae ; Gerbera jamesonii
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract When leaves of the ornamental crop Gerbera jamesonii are damaged by the spider mite Tetranychus urticae, they produce many volatile compounds in large quantities. Undamaged gerbera leaves produce only a few volatiles in very small quantities. In the headspace of spider mite-damaged gerbera leaves many terpenoids are present, comprising 65% of the volatile blend. In addition, a number of nitrogen containing compounds, such as oximes and nitriles, are produced. We studied the attraction of P. persimilis to the volatiles from spider mite-damaged gerbera leaves and how attraction is affected by starvation and previous experience. Phytoseiulus persimilis that were reared on spider mites (T. urticae) on Lima bean were not attracted to spider mite-induced volatiles from gerbera. Starvation did not influence the predator's response to these volatiles. In contrast, predators that were reared on spider mites on gerbera leaves were strongly attracted to volatiles from spider mite-infested gerbera. This was found also for predators that originated from a culture on spider mite-infested bean and were offered six days of experience with spider mites on gerbera leaves.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1020887104771
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  • 78
    Digitale Medien
    Digitale Medien
    The interface air/water of n-dodecanephosphonic acid solutions (1998)
    Springer
    Colloid & polymer science 276 (1998), S. 52-58 
    Details
    ISSN: 1435-1536
    Schlagwort(e): Key words Dodecanephosphonic acid ; soluble monolayer ; air/water interface ; evaporation ; adsorption ; ion-selective electrodes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract  The air/water interface of the system n-dodecanephosphonic acid (H2DP)–water was studied by surface tension, ion-selective electrodes and evaporation in an electrobalance. The combination of surface tension and ion-selective electrodes measurements enables to study the adsorption of soluble surfactants above the cmc using the Gibbs’ equation. H2DP formed a nonideal monolayer at the air/water interface with A molec=0.995 nm2 below the cmc. Above the cmc there was a reduction in adsorption giving A molec=6.32 nm2, which remained almost constant in the explored concentration range. This adsorption reduction may be due to a change composition on micellization, or to a thermodynamic advantage of micellization on adsorption. The reduction in the evaporation rate of water was mainly due to the reduction of the water activity, caused by the presence of solutes in bulk. This is because the strong changes in the surface coverage did not have significant influence on the evaporation rate.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s003960050208
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  • 79
    Digitale Medien
    Digitale Medien
    Synthesis of temperature-sensitive micron-sized monodispersed composite polymer particles and its application as a carrier for biomolecules (1998)
    Springer
    Colloid & polymer science 276 (1998), S. 470-475 
    Details
    ISSN: 1435-1536
    Schlagwort(e): Key words Composite particle ; temperature-sensitive ; biomolecules ; specific activity ; adsorption
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract  Temperature-sensitive micron-sized monodispersed composite polymer particles were prepared by seeded copolymerization of dimethylaminoethyl methacrylate and ethylene glycol dimethacrylate with 1.77 μm-sized monodispersed polystyrene seed particles. The change in surface property at temperature above and below 35 °C was examined by differential scanning calorimetry, trypsin activity and the adsorption/ desorption behaviors of low molecular weight cationic emulsifier as well as biomolecules.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s003960050268
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  • 80
    Digitale Medien
    Digitale Medien
    Thermodynamic study on the adsorption and micelle formation of long chain alkyltrimethylammonium chlorides (1998)
    Springer
    Colloid & polymer science 276 (1998), S. 595-600 
    Details
    ISSN: 1435-1536
    Schlagwort(e): Key words Surface tension ; adsorption ; micelle ; entropy ; energy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract The surface tension of aqueous solutions of tetradecyl-trimethylammonium chloride (TTAC) and decyltrimethylammonium chloride (DeTAC) were measured as a function of temperature at concentrations below and above the critical micelle concentration under atmospheric pressure. The entropy and energy of adsorption from the monomeric state and from the micellar state and also the entropy and energy of micelle formation for TTAC were evaluated and compared with those of dodecyltrimethyl-ammonium chloride (DTAC). The values of ΔM W s and ΔM W u for TTAC and DTAC systems show that the micelle formation is driven by the entropy at low temperatures and by the energy at high temperatures.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s003960050286
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  • 81
    Digitale Medien
    Digitale Medien
    The Influence of Carbon Surface Oxidation on the Adsorption of Methanol and Ethanol (1998)
    Springer
    Journal of thermal analysis and calorimetry 54 (1998), S. 343-350 
    Details
    ISSN: 1572-8943
    Schlagwort(e): activated carbon ; adsorption ; ethanol ; methanol ; microporosity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The influence of microporous carbon oxidation on thermodynamic properties of methanol and ethanol adsorbed at 308, 328, and 348 K was investigated. Adsorption mechanisms are suggested and the obtained results are compared with the presented previously for adsorption of methane and carbon tetrachloride on nonoxidised and oxidised microporous carbons.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010178616042
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  • 82
    Digitale Medien
    Digitale Medien
    Gravimetrically Measured Isotherms of Adsorption of Benzene, n-hexane and Cyclohexene on Different Porous Silica Gels (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 441-448 
    Details
    ISSN: 1572-8943
    Schlagwort(e): adsorption ; capillary condensation ; gravimetric method ; McBain microbalance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The isotherms of adsorption-desorption of the vapour of benzene, cyclohexene and n-hexane on different porous silica gels were measured gravimetrically. For all the adsorbates, the amount of vapour condensed in the adsorbent pores is significantly greater than the amount adsorbed. The isotherms of all the adsorbates are linear in a wide range of relative pressures.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010107416359
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  • 83
    Digitale Medien
    Digitale Medien
    Investigating a Range of Solid Samples by Automatic Water Sorption (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 581-599 
    Details
    ISSN: 1572-8943
    Schlagwort(e): adsorption ; desorption ; humidity ; hysteresis ; isotherm ; kinetic curve ; temperature test
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The CISORP Water Sorption Analyser has been used to characterise a selection of solid samples at relative humidities from 0 to 100% and at ambient pressure. The analysis reveals many interesting features about the samples and shows the scope of the equipment. Hysteresis due to porosity and differences in the physical properties of similar chemical samples show up clearly in isotherm curves. Kinetic curves reveal features such as the level of stability of dehydrated food products, changes in the hydration states of salts, and the effect of adding powdered excipient on the water sorption behaviour of a pharmaceutical compound. Kinetic curves were also used to compare the water sorption behaviour of two types of wood found inside a pine cone, and to determine equilibrium moisture sorption by calculation. It was shown that many samples take up moisture irreversibly under the experimental conditions such as amorphous sucrose and other freeze-dried samples, as well as unstable crystalline forms of compounds. Wet samples such as soaked brick and archaeological wood from a well dry out irreversibly even at 100% RH. Recording isotherms at different temperatures allows the calculation of enthalpies of water sorption. If these are compared with the enthalpy of water condensation the two processes can be compared quantitatively.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010162323145
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  • 84
    Digitale Medien
    Digitale Medien
    Calorimetric and Gravimetric Measurements of Hydrocarbon Adsorption on a Granulated Active Carbon (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 1453-1459 
    Details
    ISSN: 1572-8943
    Schlagwort(e): activated carbon ; adsorption ; calorimetry ; gravimetry ; hydrocarbon
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Adsorption isotherms of n-butane on a granulated activated carbon were measured by two different but complementary experimental methods: calorimetry and gravimetry. Adsorption heats were determined in different ways. For the system studied, the experimental results prove that the adsorbent offers a homogeneous site distribution. Besides, there can be differences between the adsorption heat values which might come from the way they are obtained (by calculation or direct measurements).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010139430558
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  • 85
    Digitale Medien
    Digitale Medien
    Sulfur isotope values in a forested catchment over four years: Evidence for oxidation and reduction processes (1999)
    Springer
    Biogeochemistry 44 (1999), S. 51-71 
    Details
    ISSN: 1573-515X
    Schlagwort(e): adsorption ; bacterial dissimilatory sulfate reduction ; dry deposition ; forested catchment ; Lake Gårdsjön ; isotopes ; oxidation of sulfur ; sulfate ; sulfur ; Sweden
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract A small catchment on the Swedish West Coast has been studied over four years to determine S dynamics by using S isotope ratios. A Norway spruce dominated forest covers the catchment, and small peat areas occur in the lower parts of the catchment. The runoff $$\delta ^{34} S_{SO_4 } $$ values varied both during the year, and from year to year. Over the period from February 1990 to December 1993, the $$\delta ^{34} S_{SO_4 } $$ values ranged from — 1%. to +11%. Over the same period, the throughfall $$\delta ^{34} S_{SO_4 } $$ values ranged from +1%. to +15%. There was no correlation (r 2= 0.01; Pr(F)=0.57) between $$\delta ^{34} S_{SO_4 } $$ values in throughfall and runoff. Since the only input of S to the catchment is atmospheric deposition, the long-term runoff S mass flux is controlled by the deposition. Therefore, processes in the catchment are responsible for the variation in the runoff $$\delta ^{34} S_{SO_4 } $$ values. During periods with $$\delta ^{34} S_{SO_4 } $$ enriched runoff, bacterial dissimilatory SO 4 2− reduction occurs in the catchment. After very dry periods, oxidation of this reduced S, which is32S-enriched, can be traced in runoff. Previous studies of the catchment have not been able to distinguish between: 1) oxidation of reduced S and dry deposition, and 2) reduction and adsorption. From the current study, it can be concluded that adsorption and dry deposition cannot cause the observed variation in runoff $$\delta ^{34} S_{SO_4 } $$ .
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00992998
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  • 86
    Digitale Medien
    Digitale Medien
    Pore Structure Tailoring of Pillared Clays with Cation Doping Techniques (1998)
    Springer
    Journal of porous materials 5 (1998), S. 227-239 
    Details
    ISSN: 1573-4854
    Schlagwort(e): pillared clays ; cation doping ; pore structure tailoring ; adsorption
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Techniques and mechanism of doping controlled amounts of various cations into pillared clays without causing precipitation or damages to the pillared layered structures are reviewed and discussed. Transition metals of great interest in catalysis can be doped in the micropores of pillared clay in ionic forms by a two-step process. The micropore structures and surface nature of pillared clays are altered by the introduced cations, and this results in a significant improvement in adsorption properties of the clays. Adsorption of water, air components and organic vapors on cation-doped pillared clays were studied. The effects of the amount and species of cations on the pore structure and adsorption behavior are discussed. It is demonstrated that the presence of doped Ca2+ ions can effectively aides the control of modification of the pillared clays of large pore openings. Controlled cation doping is a simple and powerful tool for improving the adsorption properties of pillared clay.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009682221245
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  • 87
    Digitale Medien
    Digitale Medien
    Molecular Sieves, Multifunctional Microporous Materials in Organic Synthesis (1998)
    Springer
    Journal of porous materials 5 (1998), S. 289-303 
    Details
    ISSN: 1573-4854
    Schlagwort(e): zeolites ; design ; catalysis ; shape selectivity ; adsorption ; properties ; application
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Zeolites and molecular sieves are microporous materials with an increasing number of applications. Established applications of molecular sieves are in the field of oil refining processes, selective adsorption and ion exchange. Nowadays, zeolites come to the fore as clean, selective and recyclable catalysts in petrochemistry, e.g., in aromatic alkylation. Zeolites are considered to have a high potential for the synthesis of commodities and fine chemicals due to their molecular sized pores. Nevertheless, only a few commercial applications in fine chemical synthesis are known. Based on the essential criteria, extracted from the organic reaction under consideration, some of the potential pitfalls in selecting and screening zeolites as potential catalysts are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009690423062
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  • 88
    Digitale Medien
    Digitale Medien
    High-Performance liquid chromatographic determination of dibromomannitol in plasma (1998)
    Springer
    Chromatographia 48 (1998), S. 17-19 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Dibromomannitol in plasma ; Pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Myelobromol 1,6-dibromo-1,6-dideoxy-D-mannitol (dibromomannitol, DBM) is a bifunctional alkylating agent that has been in clinical use since 1963. It is currently included at high dose in preconditioning regimen for bone marrow transplantation (BMT) and is a main-stay of treatment for polycythaemia vera. A high-performance liquid chromatographic method was developed for the determination of DBM in the plasma. The basis of the assay is a derivatization with sodium-diethyldithiocarbamate at 42°C in the presence of 1-bromo-1-deoxy-3,6-anhydro-galactitol as internal standard (IS). The analysis was carried out on a 250×4mm Hypersil 5 CPS column equipped with a 20×4 mm Hypersil 10 CPS precolumn. The eluent consisted of heptane:isopropyl-alcohol: glacial acetic acid=600:76:80 w/w. The flow rate was 1.2 mL min−1. UV detection was performed at 254 nm. The calibration graph was linear in the concentration range of 2.5–260 μM of DBM in plasma. The limit of detection was 1.0 μM. The precision and accuracy of the method was between the good laboratory practice (GLP) required limits.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467509
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  • 89
    Digitale Medien
    Digitale Medien
    Determination of cisapride in human plasma by high-performance liquid chromatography (1998)
    Springer
    Chromatographia 47 (1998), S. 537-541 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Cisapride in plasma ; Pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary An HPLC method has been developed for the quantification of cisapride in plasma for pharmacokinetic studies. Clebopride was used as internal standard. Plasma samples were extracted at alkaline pH withtert-butyl methyl ether. The organic phase was then extracted with sulphuric acid to eliminate endogenous interferences, and cisapride and the internal standard were then extracted at alkaline pH intotert-butyl methyl ether. After evaporation oftert-butyl methyl ether, the residue was analysed by HPLC. Chromatography was performed at 20°C on a 250mm×4mm i.d. reversed-phase column selective for basic compounds. The isocratic mobile phase was 48∶52 (v/v) acetonitrile-water containing 0.05 M potassium dihydrogen phosphate and 0.04 M triethylamine, adjusted to pH 5.5; the flow rate was 1 mL min−1. Cisapride and the internal standard were detected by ultraviolet monitoring at 276 nm. The calibration graph was linear for quantities of cisapride from 1 to 200 ng mL−1. Intra- and inter-day precision (CV) did not exceed 13.98%. The limit of quantitation (LOQ) was 0.68 ng mL−1 for human plasma. The applicability of the method has been demonstrated in a pharmacokinetic study of normal volunteers who received 10 mg cisapride orally.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02467491
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  • 90
    Digitale Medien
    Digitale Medien
    High-performance liquid chromatographic assay for simultaneous determination of tramadol and its active metabolite in human plasma. Application to pharmacokinetic studies (1998)
    Springer
    Chromatographia 48 (1998), S. 555-560 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Tramadol andO-demethyl tramadol in plasma ; Pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary A sensitive liquid chromatographic assay for the quantitative determination of the opioid analgesic tramadol and its active metabolite is described. Fluconazole was used as internal standard. The assay involved a singletert-butyl methyl ether extraction and LC analysis with fluorescence detection. Chromatography was at 30°C pumping an isocratic mobile phase of acetonitrile-water (19∶81, v/v) containing 0.06M NaH2PO4 and 0.05M triethylamine, adjusted to pH 7.90, at 1 mL min−1 through a reversed-phase, 250×4 mm base-stable column. The limit of quantitation of tramadol and its active metabolite was 1 ng mL−1, only 0.5 mL plasma sample was required for the determination. The calibration curve was linear from 1–1000 ng mL−1. Intra and inter-day precision (C.V.) did not exceed 10%. Mean recoveries of 96.38% for tramadol and 96.62% forO-demethyltramadol with CVs of 0.43% and 1.46% were obtained. Applicability of the method was demonstrated by a pharmacokinetic study on normal volunteers who received 100 mg tramadol intravenously.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02466649
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  • 91
    Digitale Medien
    Digitale Medien
    Rapid determination of ranitidine in human plasma by high-performance liquid chromatography (1998)
    Springer
    Chromatographia 47 (1998), S. 391-395 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Column liquid chromatography ; Ranitidine ; Plasma ; Pharmacokinetics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary An HPLC method has been developed for the quantification of rantidine in plasma for pharmacokinetic studies. Metoclopramide was used as internal standard. The method uses a simple and rapid sample clean-up procedure involving single-step extraction with organic solvent to extract ranitidine from plasma. After evaporation and reconstitution the samples are chromatographed on a 250 mm×4 mm base-stable reversed-phase column with 0.05 M ammonium acetate-acetonitrile, 75∶25 (v/v) as mobile phase and UV detection at 313 nm. The calibration graph was linear for quantities of ranitidine between 10 and 2000 ng mL−1. Intra- and inter-dayCV did not exceed 11.64%. The quantitation limit was 10 ng mL−1 for human plasma. The applicability of this method for pharmacokinetic studies of ranitidine after oral administration are described. Approximately 90 samples can be processed in 24 h.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02466469
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  • 92
    Digitale Medien
    Digitale Medien
    Observation of a Sharp Transition in Contact Angle in the Wetting of Graphite by Solid Pb-Ni Alloys (1999)
    Springer
    Interface science 7 (1999), S. 173-180 
    Details
    ISSN: 1573-2746
    Schlagwort(e): contact angle transition ; wetting ; interfacial energy ; solid pb-Ni/graphite system ; adsorption
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Abstract The wetting of Pb-Ni crystals on graphite has been observed at 558 K in a Scanning Auger Microprobe. Samples were prepared so as to produce 10 μm crystals of Pb with Ni contents increasing from 0 to 0.3 wt% along one axis of the graphite substrate. In the low Ni region, the contact angle was found to decrease slowly from 119° to 98° with increasing Ni content. In the region of high Ni content, a constant contact angle of 83° was measured. In between, crystals with contact angles of 98° and 83° were observed to coexist, near the limit of solubility of Ni in Pb, indicating the presence of a first order transition in contact angle. The continuous decrease in contact angle, in the low Ni region, is due to Ni adsorption at the Pb-graphite interface, which leads to a decrease in interfacial energy. The constant contact angle in the high Ni region is associated with the precipitation of a Ni-rich phase. Various hypotheses are advanced to account for the first order transition in contact angle as a function of Ni concentration.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008779501606
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  • 93
    Digitale Medien
    Digitale Medien
    The Geometric and Thermodynamic Properties of Grain Boundary Junctions (1999)
    Springer
    Interface science 7 (1999), S. 251-271 
    Details
    ISSN: 1573-2746
    Schlagwort(e): triple junctions ; taxonomy ; dimensionality ; structure ; energy ; segregation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Physik
    Notizen: Abstract We provide an overview of the properties of triple junctions and quadruple points. It is shown that these junctions may exhibit distinct behaviors that imply that they have and thermodynamically distinct properties in the same way that grain boundaries can be considered as thermodynamically distinct phases, separate from the material that they inhabit. It is shown that the treatment of triple junctions as thermodynamically distinct defects is a natural extension of the treatment of grain boundaries, and that it can be further extended to other junctions such as quadruple nodes. Equilibrium dihedral angles under conditions of anisotropic interfacial energy are explored, and it is found that the dihedral angles may be variable under a range of different conditions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008769209265
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