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  • Articles  (182)
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  • Column liquid chromatography  (124)
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  • Articles  (182)
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  • Springer  (182)
  • American Geophysical Union
  • Cell Press
  • International Union of Crystallography
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  • 1
    Electronic Resource
    Electronic Resource
    Catalytic disruption and volatilization of rhodium particles on silica in NO + CO (1992)
    Springer
    Catalysis letters 14 (1992), S. 141-148 
    Details
    ISSN: 1572-879X
    Keywords: Rhodium ; silica ; catalyst microstructure ; disruption ; carbon monoxide ; nitric oxide ; model catalysts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Initially reduced ≈ 100 Å diameter Rh metal particles on SiO2 are found by TEM to be dispersed into an amorphous metal film by treatment in 5% NO + 5% CO in He at 260 °C, leaving thin rings around the perimeter of the original particles. Electron diffraction shows that Rh is amorphous while XPS shows that the Rh is approximately zero valent in the dispersed state. Continued heating in this mixture resulted in irreversible volatilization of the Rh even at these low temperatures. Subsequent heating in H2 at 650 °C caused sintering and the reformation of crystalline Rh particles, but with a lower loading than observed initially. Treatment of Rh particles in 5% NO at 260 °C causes Rh particles to shrink in diameter and to form thin shells around their perimeters. The only change observed after treatment in 5% CO alone at 260 °C was slight sintering of adjacent Rh particles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00765228
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  • 2
    Electronic Resource
    Electronic Resource
    Relation between preparation, porosity and selectivity of CuO-ZnO-MeO x catalysts in the synthesis of alcohol mixtures (1992)
    Springer
    Catalysis letters 14 (1992), S. 185-195 
    Details
    ISSN: 1572-879X
    Keywords: CuO-ZnO-MeO x catalysts ; characterization by XRD ; DTA ; adsorption ; alcohol synthesis ; C2-C5-OH selectivity ; influence of porosity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Some relations between the preparation of modified CuO-ZnO catalysts, their structural properties and their catalytic performance in the hydrogenation of carbon monoxide have been demonstrated. The different activities in the formation of higher alcohols have been attributed to an influence of the porosity on chain growth. The coupling or insertion of C1 intermediates seems to be favoured by an increasing surface coverage with C1 intermediates due to a transport limitation of methanol production. The pore size distribution of the catalysts has been varied by different calcination, thermal ageing, CuO/ZnO ratios, the method of promoting with Al2O3 and pelleting.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00765232
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  • 3
    Electronic Resource
    Electronic Resource
    Composition of Pd-La/α-Al2O3 catalysts (1992)
    Springer
    Catalysis letters 16 (1992), S. 323-334 
    Details
    ISSN: 1572-879X
    Keywords: Palladium ; lanthanum ; lanthanum oxide ; lanthanum aluminum oxide ; α-alumina ; X-ray diffraction (XRD) ; temperature-programmed reduction (TPRd) ; nitric oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The objective of this study is to investigate the structure of the Pd-La/α-Al2O3 catalyst. X-ray diffraction (XRD) and temperature-programmed reduction (TPRd) were used as characterization techniques. Contrary to the assertions in the literature, XRD studies conducted on La/α-Al2O3 composite oxides and Pd-La/α-Al2O3 catalysts show that Pd catalyzes the solid state reaction between A12O3 and Al2O3 to form LaAlO3. TPRd studies conducted on Pd/α-Al2O3, Pd/La2O3, Pd/LaAlO3, and Pd-La/α-Al2O3 catalysts suggest that Pd in the Pd-La/α-Al2O3 catalyst interacts more strongly with LaAlO3 than with α-Al2O3. Reaction studies were conducted to investigate the activity of Pd/α-Al2O3, Pd/La2O3, Pd/LaA103, and Pd-La/α-Al2O3 catalysts for nitric oxide (NO) reduction. These studies show that Pd/LaAlO3 catalysts are most active for NO removal at stoichiometric and under net reducing conditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00764344
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  • 4
    Electronic Resource
    Electronic Resource
    Simultaneous catalytic reduction of sulfur dioxide and nitric oxide (1999)
    Springer
    Catalysis letters 62 (1999), S. 127-130 
    Details
    ISSN: 1572-879X
    Keywords: simultaneous reduction ; sulfur dioxide ; nitric oxide ; carbon monoxide ; carbonyl sulfide ; lanthanum oxysulfide ; cobalt disulfide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The present work reports a catalytic system for the simultaneous reduction of SO2 and NO using CO as a reducing agent. The catalyst contains lanthanum oxysulfide and cobalt sulfides. Experimental results showed that at temperature above 450°C, SO2 and NO conversions are greater than 98 and 99%, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019075828527
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  • 5
    Electronic Resource
    Electronic Resource
    Selective catalytic reduction of nitric oxide with ammonia on Mn‐promoted carbonized used silica–alumina sorbents (1999)
    Springer
    Catalysis letters 63 (1999), S. 107-111 
    Details
    ISSN: 1572-879X
    Keywords: selective catalytic reduction ; nitric oxide ; ammonia ; Mn‐promoted silica–alumina
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Deactivated (waste) silica–alumina sorbents were carbonized and used as supports. The introduction of manganese led to active and selective SCR catalysts at low temperatures. Two methods of Mn promoting were compared: wet impregnation and adsorption. They influenced the distribution of Mn and N2O production. The catalysts behaved similarly to Mn‐promoted active carbon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019056718957
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  • 6
    Electronic Resource
    Electronic Resource
    Thermal study of synthesis of cryptohalite (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 475-486 
    Details
    ISSN: 1572-8943
    Keywords: synthesis of cryptohalite ; DTA ; Crystalloflex diffractometer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Mittels eines Derivatographen wurde die Synthese von Kryptohalit (Ammoniumsiliziumhexafluorid) durch Sintern von Quarz mit Ammoniumfluorid thermisch untersucht. Die Reaktionsprodukte wurden mikroskopisch und mit Hilfe eines Siemens-Crystalloflex Diffraktometers identifiziert. Die DTA-Kurven zeigen, da\ die intensive Bildung von Kryptohalit in einer endothermen Reaktion bei 125
    Notes: Abstract The present work represents a thermal study of synthesis of cryptohalite (Ammonium silicon hexafluoride) by sintering of quartz with ammonium fluoride using a derivatograph. The reaction products were identified microscopically and by using a Siemens Crystalloflex diffractometer. The DTA curves indicate that the intensive formation of cryptohalite takes place at 125
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01915512
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  • 7
    Electronic Resource
    Electronic Resource
    Thermal decomposition of sodium nitrite and sodium nitrate pre-adsorbed on TiO2 surfaces (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 673-682 
    Details
    ISSN: 1572-8943
    Keywords: DTA ; pre-adsorbed sodium nitrite/nitrate ; solid state chemical reaction ; TPD-MS method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Mittels verschiedenen Techniken, wie z.B. IR-Spektroskopie oder temperaturprogrammierte Desorption in Verbindung mit massenspektrometrischer Analyse wurde die thermische Zersetzung von Natriumnitrit oder Natriumnitrat, welches zuvor an der Oberfläche von TiO2 absorbiert wurde, untersucht, um die Eigenschaften bei dieser thermischen Zersetzung zu beobachten. DTA in Verbindung mit Röntgendiffraktions-analyse wurde eingesetzt, um die Möglichkeit einer chemischen Feststoffreaktion zwischen den bei der thermischen Zersetzung der voradsorbierten Proben entstehenden Produkten und TiO2 zu untersuchen. Anhand der Ergebnisse werden zahlreiche verschiedene charakteristische Wesenszüge dieser thermischen Zersetzung diskutiert.
    Notes: Abstract The thermal decomposition of sodium nitrite or nitrate pre-adsorbed upon TiO2 surfaces has been investigated by employing several techniques as infrared spectroscopy (IR) and temperature programmed desorption in conjunction with mass spectrometry analysis (TPD-MS) to study the features observed during these thermal decompositions. Differential thermal analysis (DTA) in combination with X-ray diffraction analysis (XRD) were used to investigate the possibility of a solid state chemical reaction between the solid products originated from the thermal decomposition of the pre-adsorbed species and the TiO2. On the basis of our results, various characteristic features of these thermal decomposition reactions will be discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01979396
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  • 8
    Electronic Resource
    Electronic Resource
    Thermal methods and microcalorimetry application in the studies of low energy cements (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 771-775 
    Details
    ISSN: 1572-8943
    Keywords: cement clinkerization ; DTA ; microcalorimetry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung In einer DTA-Studie des Klinkerbildungsprozesses wurden die Enthalpiewerte der einzelnen Stufen der Klinkersynthese bestimmt. Die ermittelte Abnahme der Energieaufnahme für die Änderung der Phasenzusammensetzung beträgt 400 J/g. Mittels Mikrokalorimetrie und thermischen Methoden konnte die Aktivierung des energetisch niedrig liegenden Zementes durch Zusatz von Ba nachgewiesen werden.
    Notes: Abstract In the DTA studies of the clinkerization process the values of enthalpy attributed to the particular stages of clinker synthesis were determined and the energy consumption decrease due to the modification of the phase composition was calculated for 400 J/g. The activation of the low energy cement by Ba addition was shown using microcalorimetry and thermal methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01979407
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  • 9
    Electronic Resource
    Electronic Resource
    DTA study of the hydration of systems of interest in the field of building materials manufacture (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 761-770 
    Details
    ISSN: 1572-8943
    Keywords: building materials ; DTA ; hydration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Mittels DTA wurden die Hydratationsprozesse von Gemischen aus Gips, Hochofenschlacke oder Flugasche, Portlandzement und/oder Löschkalk untersucht, die zur Bildung von Calciumtrisulfoaluminat und Silikathydraten fähig sind. Die Proben wurden bei 55°, 70° und 85°C für 16, 24 und 48 Stunden lang, im Anschluß daran durch Aushärten bei Raumtemperatur und normaler Luftfeuchte 28 Tage lang gealtert. Bei der Verwendung von Schlacke beträgt die optimale Vorhärtungstemperatur 55°C und die Erhöhung der Vorhärtungsperiode von 16 auf 48 Stunden ließ den Hydratationsgrad unverändert. Bei der Verwendung von Flugasche beträgt die optimale Vorhärtungstemperatur 85°C. Die Erhöhung der Vorhärtungsperiode von 16 auf 14 Stunden steigert auch den Hydratationsgrad. Eine weitere Steigerung auf 48 Stunden setzt die Selektivität gegenüber Calciumtrisulfoaluminat-Hydrat herab. In keinem der untersuchten Systeme hatte das Nachhärten bei Raumtemperatur und normaler Luftfeuchte einen signifikanten Einfluß auf den Hydratationsgrad. Letztendlich hängt der Einfluß der Ausgangsmaterialien nicht nur von den Eigenschaften jeder einzelnen Komponente, sondern auch von denen der anderen Komponenten ab.
    Notes: Abstract The hydration processes of mixtures containing calcined gypsum, blastfurnace slag or fly ash, portland cement and/or hydrated lime, able to generate calcium trisulphoaluminate and silicate hydrates, have been studied by means of differential thermal analysis. Samples were aged at 55°,70° and 85°C for 16, 24 and 48 hours, followed by a further curing at room temperature and humidity up to 28 days. In the case of the systems containing slag, the optimum pre-curing temperature is 55°C and increasing the pre-curing time from 16 to 48 hours leaves the hydration degree almost unchanged. In the case of the systems containing fly ash the optimum pre-curing temperature is 85°C. Increasing the pre-curing time from 16 to 24 hours enhances the hydration degree. The further increase to 48 hours reduces the selectivity towards calcium trisulphoaluminate hydrate. In all the systems investigated the post-curing at room temperature and humidity has no significant effect on the hydration degree. Finally, the influence of the nature of raw materials depends not only on the characteristics of each component, but also on those of the others.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01979406
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  • 10
    Electronic Resource
    Electronic Resource
    Thermal decomposition of silver cyano complex and characterization its decomposition products by ETA, DSC, DTA and TG (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 789-796 
    Details
    ISSN: 1572-8943
    Keywords: ETA ; DSC ; DTA ; silver cyano complex ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Mittels DTA und TG wurde [Phenyl2I][Ag(CN)2] untersucht in im festen Zustand bei Erhitzen in einer Argonatmosphäre bis 160°C als thermisch stabil befunden. Beim Erhitzen auf höhere Temperaturen erfolgt eine Zersetzungsvorgang, wobei flüchtige Produkte wie z.B. [Phenyl]I, [Phenyl]NC und (CN)2 entstehen. Bei Erhitzen auf 500°C erhält man metallisches Silber. Die festen Zwischen- und flüchtigen Produkte wurden mittels IR-Spektroskopie untersucht. Anhand der DTA- und ETA-Untersuchungen konnte festgestellt werden, daß bei Erhitzen und Abkühlen unterhalb 100°C reversible Einphasenumwandlungen stattfinden. Bei Erhitzen über 100°C schmilzt die Probe (SchmelzpunktT m=135°C). Die Schmelzenthalpie wurde mittels DSC ermittelt (H=−28 kJ/mol). Mit Hilfe von ETA wurde der Unordnungsgrad des Zersetzungsendproduktes geschätzt. Der Wert der Aktivierungsenergie für die Radondiffusion im Temperaturbereich 720°–500°C beträgt 32,6 kJ/mol.
    Notes: Abstract It was found by DTA and TG that [Phenyl2I][Ag(CN)2] in the solid state is chemically stable on heating in argon up to 160°C. During heating to higher temperatures it decomposes, forming volatile products such as [Phenyl]I, [Phenyl]NC and (CN)2 [1]. After heating the sample to 500°C metallic silver resulted. The volatile and intermediate solid products were analysed by IR-spectroscopy. It was found by means of DTA and ETA that an isophase reversible transition takes place when the sample is heated and cooled, not higher than 100°C. At heating higher than 100°C the sample melts (melting pointT m=135°C). The enthalpy melting was determined by means of DSC (ΔH=−28 kJ·mol−1). By means of ETA the disorder degree of the final decomposition product was estimated. The value of the activation energy of radon diffusion in the temperature range 720°–500°C equals 32.6 kJ·mol−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01979410
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  • 11
    Electronic Resource
    Electronic Resource
    Thermal analysis of renal stones (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 1671-1682 
    Details
    ISSN: 1572-8943
    Keywords: DTA ; IR ; renal stones ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Mittels TG und DTA wurde die chemische Zusammensetzung von 200 Nierensteinen untersucht, die in den Gebieten Taxila, Rawalpindi und Islamabad in Indien gesammelt wurden. Die Thermogramme zeigen Masseverluste bei verschiedenen Temperaturen, die auf Dehydratation und Zersetzung der Nierensteine hinweisen. Die Ergebnisse wurden mit den qualitativen Resultaten aus der IR-Analyse verglichen, welche die chemische Zusammensetzung der verschiedenen Steine im festen Zustand bekräftigte. Die Thermogramme halfen bei der Unterscheidung von verschieden gebundenem Wasser, ihre chemische Zusammensetzung wurde durch Gewichtsverlust bei der Pyrolyse bestimmt. Man fand, daß 26.5 % der Steine aus reinem Whewellit bestanden, 3 % aus Weddellit, 13 % aus anhydrierter Harnsäure, 7.5 % aus Struvit, 2.5 % aus Ammmoniumhydrogenurat, 0.5 % aus Cystin und 47 % der Steine hatten eine gemischte Zusammensetzung. Die häufigsten Kombinationen der Mischzusammensetzungen waren Calciumoxalat mit Harnsäure (14.5 %) und mit Phosphaten (27.5 %).
    Notes: Abstract The chemical composition of 200 renal stones, collected from Taxila, Rawalpindi and Islamabad regions in Pakistan, was determined by thermogravimetric (TG) and differential thermal analysis (DTA) techniques. The thermal curves show weight losses at various temperatures indicating dehydration and decomposition phenomena of renal stones. Results were compared with qualitative data obtained by IR analysis which confirmed the chemical composition of various stones in the solid state. The thermal curves helped in the differentiation of various kinds of water held by stones and their chemical composition was obtained by weight loss during pyrolysis. It was found that 26.5% of the stones were pure whewellite, 3% weddellite, 13% uric acid anhydrous, 7.5% struvite, 2.5% ammonium acid urate, 0.5% cystine and 47% stones had mixed composition. In the mixed state the most frequent combinations were those of calcium oxalate with uric acid (14.5%) and with phosphates (27.5%).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01979363
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  • 12
    Electronic Resource
    Electronic Resource
    The application of thermal analysis and conduction calorimetry on the formation and hydration of calcium aluminoferrite (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 2147-2155 
    Details
    ISSN: 1572-8943
    Keywords: calcium aluminoferrite ; conduction calorimetry ; DTA ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Mittels DTA wurde die Bildung von Calciumaluminoferrit aus CaO, Al2O3 und Fe2O3 im Verhältnis 2∶x∶1−x (mitx=0−3/4) sowie der Einfluß von C4A3S, C11A7CaF2, ß-C2S und MgO auf diesen Prozeß untersucht. Die Bildung wird durch die Schmelze von CF und das Eutektikum von CaO-Fe2O3, CA-C12A7, CA-C3A, C12A7, CA-C3A und CA-C2AxF(1−x) begünstigt. Durch Gegenwart von ß-C2S und MgO wird die Bildungstemperatur durch ein zusätzliches Eutektikum herabgesetzt, während C4A3S und C11A7CaF2 dies nicht bewirken. Mit Hilfe eines von uns hergestellten Konduktions-Kalorimeters wurde die frühe Wärmeentwicklung während der Hydratation von C2AxF(1−x)-gemessen und die Produkte nach einer 1-tägigen Hydratation mittels TG und DTA untersucht. Die Ergebnisse zeigten, daß mit einem steigenden Wert für x die Peaks der Wärmeentwicklung größer werden, die Menge des Hydratationsproduktes Eisenhydratgel abnimmt und CAH10 und C3(A,F)H6 ebenfalls mehr werden Je mehr MgO (bis zu 5%) in C6AF2 gelöst ist, umso höher ist die Hydratationswärme für diesen Mischkristall. Wird in C6AF2 2% TiO2 gelöst, erreicht die Hydratationswärme ihr Maximum für dieses System.
    Notes: Abstract DTA was used to study the formation of calcium aluminoferrite from CaO, Al2O3 and Fe2O3 (proportion=2∶ x∶ 1−x),x=0-3/4) and the effects of C4A3 $$\mathop S\limits_{\text{\_}}^{\text{\_}} $$ C11 A7·CacF2, β-C2S and MgO on that process. The fusion of CF and the eutectic of CaO-Fe2O3, CA-C12A7, CA-C3A, C12A7-CA-C3A and CA-C2AxF(1−x) will be favourable for the formation. The presence of β-C2S and MgO will decrease its formation temperature by an extra eutectic while C4A3 $$\mathop S\limits_{\text{\_}}^{\text{\_}} $$ . and C11A7·CaF2 will not. The early heat evolution during the hydration of C2AxF(1−x) were measured by the conduction calorimeter made by ourselves and the products after 1 day hydration were examined by TG and DTA. The results revealed that the peak of heat evolution rise, the amount of the hydrating product iron hydrate gel decreases, CAH10 and C3(A, F)H6 increase with the increase of the value x. The more MgO (up to 5%) soluted in C6AF2, the higher the hydration heat for this solid solution is, when TiO2 soluted in C6AF2 is 2%, the hydration heat for the system reaches the highest.
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    URL: http://dx.doi.org/10.1007/BF01979628
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  • 13
    Electronic Resource
    Electronic Resource
    Thermal Degradation of Cotton Cellulose (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 93-98 
    Details
    ISSN: 1572-8943
    Keywords: degradation ; DTA ; flame retardant ; IR ; pyrolysis ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal degradation of cotton cellulose treated with chemical mixtures containing P and N was studied by thermal analysis, infrared spectroscopy, Char yield and limiting-oxygen-index (LOI). Our experiments demonstrated the following facts. The temperatures and activation energies of pyrolysis were lower for cotton cellulose treated with flame retardants than those for untreated samples and the values of Char yield and LOI were greater for treated cotton than those for untreated one.
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    URL: http://dx.doi.org/10.1023/A:1010132121811
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  • 14
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    Electronic Resource
    Thermal Stability of γ-irradiated Tolbutamide (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 291-300 
    Details
    ISSN: 1572-8943
    Keywords: DTA ; γ-radiation doses ; IR ; thermal stability ; tolbutamide ; UV
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal stability of tolbutamide before and after exposure to various γ-radiation doses was investigated. The data were followed by studying DTA, X-ray diffraction, IR, and UV absorption spectra before and after γ-irradiation. The results obtained were promising, and were explained, and discussed on the basis of γ-enhanced stabilization through recombination of free radicals.
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    URL: http://dx.doi.org/10.1023/A:1010129415876
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  • 15
    Electronic Resource
    Electronic Resource
    Phase Relations in the CoMoO4-CoV2O6-CoO System Quasi-Binary Line Co3V2O8-CoMoO4 (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 211-215 
    Details
    ISSN: 1572-8943
    Keywords: cobalt(II) orthovanadate-cobalt(II) molybdate system ; cobalt(II) vanadium(V) molybdenum(VI) oxide ; DTA ; phase diagram ; XRD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The phase relationship in the pseudobinary Co3V2O8-CoMoO4 system have been determined by differential thermal analysis (DTA) and X-ray diffraction (XRD). A new compound Co2.5 VMoO8, stable up to 1080±5°C has been found in the system. The results obtained are presented in the form of a phase diagram.
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    URL: http://dx.doi.org/10.1023/A:1010141004962
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  • 16
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    Characterization of Cinchonidine Doped Montmorillonite Supported Noble Metal Catalysts by Thermoanalytical Methods (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 337-343 
    Details
    ISSN: 1572-8943
    Keywords: DTA ; DTG ; immobilized cinchonidine ; Pt/K-10 montmorillonite ; TG ; thermal stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The characterization of new cinchonidine doped K-10 montmorillonite supported noble metal catalysts is described. Our aim was the mapping of thermal stability of these new catalytic materials by thermogravimetry (TG), differential thermogravimetry (DTG) and differential thermoanalysis (DTA) methods accompanied by X-ray diffraction (XRD) measurements. The catalysts were prepared by various methods including conventional, microwave and ultrasonic treatments. They were characterized first by X-ray diffraction to verify the stability of montmorillonite crystal structure during preparation. Then, TG and DTG methods were applied to determine their stability under the experimental conditions usually applied. The main changes observed were the loss of water and the decomposition of the organic modifiers in the higher temperature region. The catalyst showed the best performance were prepared and characterized using microwaves and ultrasonic irradiation in order to get more insight to the effect of preparation methods on their stability. As a consequence, the catalysts were found to be stable and regenerable under 450-500 K, however, higher temperatures resulted in the complete destruction of the catalysts.
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    URL: http://dx.doi.org/10.1023/A:1010198500844
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  • 17
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    A Thermoanalytical Study of Copper(I) Thiocarbamide Compounds (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 479-484 
    Details
    ISSN: 1572-8943
    Keywords: copper thiocarbamide complex ; DTA ; spray pyrolysis ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Hydrated isostructural 1:3 complexes of copper(I) chloride and bromide with thiourea were synthesised and their thermal decomposition studied by simultaneous TG/DTA complemented by ex situ FTIR and XRD studies. The decomposition of Cu(tu)3Cl·H2O is initiated by dehydration around 100°C, followed by a total multi-step degradation of the structure in the temperature range of 200–600°C. The counter ion has some influence on the temperatures and composition of the solid residue. The results were compared with those obtained with the 1:1 complex Cu(tu)Cl·1/2H2O.
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    Thermochemical Properties of Chemically Modified Zeolite (1999)
    Springer
    Journal of thermal analysis and calorimetry 58 (1999), S. 671-675 
    Details
    ISSN: 1572-8943
    Keywords: chemically modified zeolite thermochemical properties ; DTA ; emanation thermal analysis ; TG ; zeolite
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Zeolites chemically modified with 1, 4 or 6 M aqueous solutions of NaOH were studied by DTA, TG and ETA (emanation thermal analysis) in the temperature range 201–200°C. The structural changes in the modified zeolites at room temperature and in the modified zeolites annealed at 1000°C were studied by XRD analysis. Thermal analysis demonstrated dehydration, dehydroxylation, structural changes and a glass transition. A gradual loss in crystallinity of the chemically modified zeolites was also observed. XRD analysis revealed structural changes caused by chemical treatment and also by annealing.
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    URL: http://dx.doi.org/10.1023/A:1010121031760
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    Transformation-Governed Heating Techniques in Thermal Analysis II. (1999)
    Springer
    Journal of thermal analysis and calorimetry 58 (1999), S. 725-739 
    Details
    ISSN: 1572-8943
    Keywords: DDC ; DSC ; DTA ; transformation-governed TA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The described instrumental method makes it possible that the quasi-static heating technique, well applicable to thermogravimetric measurements, (see Part I of this paper) can be used in the case of DTA and DSC examinations, too. Based on the new type of curves the characteristic transformation temperatures, the whole course of the transformation in dependence of sample temperature, the extent of the enthalpy change caused by the transformation or by its partial processes can accurately be determined. The essentially greater accuracy of the measurements — in comparison to the conventional ones — is due to the quasi-static heating technique which ensures that the transformations should take place under quasi-equilibrium conditions.
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    URL: http://dx.doi.org/10.1023/A:1010181217648
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    The Thermal Decomposition of Manganese Carbonate Thermogravimetry and Exoemission of Electrons (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 227-232 
    Details
    ISSN: 1572-8943
    Keywords: DTA ; DTG ; exoemission of electrons ; Gibbs energy ; manganese carbonate ; manganese oxides ; phase change
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Results are reported on the thermal decomposition of manganese carbonate, MnCO3. Thermogravimetry (TG), differential thermogravimetry (DTG), and differential thermoanalysis (DTA) curves were recorded simultaneously and depicted together with the curve of intensity of electron exoemission (EEE).
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    URL: http://dx.doi.org/10.1023/A:1010165029080
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    Thermal Decomposition of Strontium and Barium Malonates (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 789-796 
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    ISSN: 1572-8943
    Keywords: alkaline earth malonates ; DSC ; DTA ; kinetic parameters ; TG ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal decomposition of strontium and barium malonates has been studied isothermally and non-isothermally employing simultaneous TG-DTG-DTA, DSC, XRD and IR spectroscopic techniques. DSC of these malonates has been recorded both in oxygen and nitrogen atmospheres. The decomposition is a single step process and the end product formed is carbonate. The energy of activation and frequency factor values for the decomposition of strontium malonate are 547 kJ mol−1 and 1041 s−1 respectively. The activation energy and frequency factor values for isothermal dehydration of barium malonate sester-hydrate are 57–111 kJ mol−1 and 107–1012 s−1 respectively and the corresponding values for decomposition from DSC are 499.5 kJ mol−1 and 1044 s−1 respectively. The higher thermal stability of strontium malonate as compared to that of barium salt is ascribed to its being anhydrous so that decomposition proceeds without restructuring. Their thermal stabilities have also been compared with that of respective oxalate salts.
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    URL: http://dx.doi.org/10.1023/A:1010169414001
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    From Precursors to Thin Films - Thermoanalytical Techniques in the Thin Film Technology (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 7-15 
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    ISSN: 1572-8943
    Keywords: ALE ; CVD ; DSC ; DTA ; EGA ; EL display ; solar cell ; sol-gel ; spray pyrolysis ; super-conductor ; TG ; thin films
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Processing thin films for advanced applications, for instance in electronics and optoelectronics, involves several steps starting from precursor synthesis and ending up with the devices. Especially when optimizing the first steps of this chain of processes, thermoanalytical techniques play an important role. The review will focus on the main chemical deposition methods (CVD, ALE, spray pyrolysis, sol-gel) giving selected examples of problem-solving by thermal analysis. The techniques discussed are TG, DTA/DSC, EGA and their combinations. High-temperature X-ray diffraction (HTXRD) is also a powerful tool for in situ studies of thin films. The examples are taken from solar cell, superconductor and flat panel electroluminescent display technologies.
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    URL: http://dx.doi.org/10.1023/A:1010154818649
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    Reaction Mechanism of Fe8W10W16O85 Synthesis (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 419-422 
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    ISSN: 1572-8943
    Keywords: DTA ; IR ; reaction mechanism ; XRD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The reaction mechanism of the synthesis of Fe8V10W16O85 was studied by means of XRD, IR spectroscopy and DTA techniques. It was found that the intermediate in the reaction may be either FeVO4 or FeVO4 admixed with an unidentified phase X, depending on the reaction temperature. The IR spectrum of the phase Fe8V10W16O85 is reported for the first time.
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    URL: http://dx.doi.org/10.1023/A:1010123306296
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    Thermal Analysis and X-Ray Diffraction of Roasting of Egyptian Molybdenite (1999)
    Springer
    Journal of thermal analysis and calorimetry 57 (1999), S. 415-431 
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    ISSN: 1572-8943
    Keywords: DTA ; roasting of molybdenite ; XRD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Molybdenite is the main ore mineral for the molybdenum industry and the production of molybdenum. The industrial processing of molybdenite is based on its oxidized roasting to technical grade molybdenum oxide, followed by its purification by distillation or its ammonia leaching. The present work reports a thermal analysis study of the oxidized roasting of Egyptian molybdenite, using a derivatograph. The reaction products were identified microscopically and by using a Siemens Crystalloflex diffractometer. The DTA curves of the roasting of molybdenite show that its oxidation begins at 360–370°C, as indicated by the small exothermic peak at such temperatures. This is followed immediately by a large, wide exothermic peak with maximum at 510–520°C, representing the intensive oxidation of molybdenite. The medium endothermic peak at 795–800°C reflects the melting and sublimation of molybdenum oxide. The vigourous vaporization of molybdenum oxide and its boiling are associated with the large, sharp endothermic peak at 1150°C. This is accompanied by a large loss in mass (TG). The study includes calculation of the thermodynamic constants and the kinetics of the reaction of oxidation of molybdenite. The oxidized roasting of molybdenite results in the production of molybdenum oxide, which is the essential starting material of the molybdenum industry. The molybdenum oxide produced has the molybdite structure and crystallizes in the orthorhombic system in the form of elongated, thin, light-green crystals.
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    URL: http://dx.doi.org/10.1023/A:1010151605309
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    Thermal and calorimetric studies of M(IO3)2·6H2O and M(IO3)2·6D2O forM 2+=Ca2+ and Sr2+ (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 2491-2499 
    Details
    ISSN: 1572-8943
    Keywords: DSC ; DTA ; M(IO3)2· 6H2O ; M(IO3)2·6D2O
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Mittels DTA- und DSC-Methoden wurden Me(IO3)2·6H2O und Me(IO3)2·6D2O (mitMe 2+=Ca2+ und Sr2+) thermisch und kalorimetrisch untersucht. Es wird ein Überblick über das thermische Verhalten ordentlicher und deuterierter Hydrate gegeben, in dem auch die Unterschiede zwischen beiden diskutiert werden. Die Enthalpien der untersuchten Phasenumwandlungen wurden bestimmt. Aus den Daten für Hdeh wurde Hf von Ca(IO3)2·6H2O, Ca(IO3)2H2O(D2O) und Sr(IO3)2·6H2O(D2O) berechnet und Bemerkungen zum beobachteten Isotopeneffektes gemacht.
    Notes: Abstract Thermal and calorimetric studies were carried out on M(IO3)2·6H2O and M(IO3)2·6D2O forM 2+=Ca2+ and Sr2+, using DTA and DSC methods. The thermal behaviour of the ordinary and deuterated hydrates is outlined and the differences observed between them are discussed. The enthalpies of the phase transitions were determined. The ΔH f o for Ca(IO3)2·6H2O, Ca(IO3)2·6H2O(D2O) and Sr(IO3)2·6H2O(D2O) were calculated from the ΔH deh data and comments are made on the isotope effect observed.
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    URL: http://dx.doi.org/10.1007/BF01974627
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    Thermal behaviour and vibrational characterization of MH2(IO3)3 phases (M=K, Rb and NH4) (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 2593-2602 
    Details
    ISSN: 1572-8943
    Keywords: isomorphous compounds ; solid protonic conductors ; TG ; DTA ; XRD ; IR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Als Teil einer Studie der Eigenschaften von Feststoff-Protonenleitern wurde neben den IR- und Raman-Spektren auch das thermische Verhalten der isomorphen Verbindungen MH2(IO3)3 (M=K, Rb, NH4) untersucht. In den drei Phasen wurden mit Hilfe von TG, DTA, IR und Röntgendiffraktionsuntersuchungen detaillierte Stöchiometrien entwickelt. Es gab auch Beweise für die Bildung von polymeren [I3O8]− Phasen. Ihre Stabilität steht in Verbindung mit der unterschiedlichen Polarisationsfähigkeit der H-, K- und Rb-Kationen.
    Notes: Abstract The thermal behaviour of the MH2(IO3)3 (M=K, Rb and NH4) isomorphous compounds, as well as the IR and Raman spectra have been investigated as part of a study of the properties of solid protonic conductors. Detailed stoichiometries, sustained by TG, DTA, XRD and IR analysis, have been developed into the three phases. There were also evidences of the formation of the [I3O8]− polymeric phases. Their stabilities were associated to the different polarizing power of the H, K and Rb cations.
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    New reference materials for the calibration (temperature and energy) of differential thermal analysers and scanning calorimeters (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 855-863 
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    ISSN: 1572-8943
    Keywords: calibration materials ; DSC ; DTA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Als neue Referenzsubstanzen für Temperatur- und Energiekalibrierung von DTA- und DSC-Geräten wurden im Temperaturbereich 300–600 K einige organische Verbindungen, wie z.B. Phenanthren, Benzanilid, Anissäure, Triphenylen, 2-Chloranthrachinon, Hexachlorbenzol, Karbazol, 4-Jodbenzoesäure, Perylen und Anthrachinon untersucht.
    Notes: Abstract Several organic compounds like phenanthrene, benzanilide, anisic acid, triphenylene, 2-chloroanthraquinone, hexachlorobenzene, carbazole, 4-iodobenzoic acid, perylene, anthraquinone, as new reference materials for temperature and energy calibration of DTA and DSC apparatuses were studied in the range 300—600 K.
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    Thermal behaviour of amorphous Li2ZrO3 prepared by sol-gel technique (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 567-573 
    Details
    ISSN: 1572-8943
    Keywords: Emanation Thermal Analysis ; dilatometry ; DTA ; TG ; lithium-based oxide ceramics ; sol-gel technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Ergebnisse aus Untersuchungen des thermischen Verhaltens von Li2ZrO3, hergestellt mittels einer Sol-Gel-Technik im amorphen Zustand werden dargelegt. Die thermische Behandlung wurde in Luft bei einer konstanten Aufheizgeschwindigkeit von 5 Grad·min−1 und einer Abkühlgeschwindigkeit von 2,5Grad·min−1 durchgeführt. Zur Beschreibung des thermischen Verhaltens unter dynamischen Verhältnissen wurden DTA, TG, Emanationsthermoanalyse und Dilatometrie angewendet. Zur näheren Charakterisierung der bei TG beobachteten Phasenumwandlungen wurde Röntgendiffraktion verwendet.
    Notes: Abstract The results of the investigations of thermal behaviour of Li2ZrO3, prepared in the amorphous state by means of sol-gel technique are demonstrated. The thermal treatment was carried out in air under constant heating rate of 5 deg·min−1 and cooling rate of 2.5 deg·min−1. The methods of DTA, TG, Emanation Thermal Analysis (ETA) and dilatometry were used, for characterization of the thermal behaviour in dynamic conditions. The X-ray diffraction patterns were used for characterization of the phase changes observed by TA Methods.
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    Comparative investigation of several types of γ-Fe2O3 ferro-powders by the methods of thermal analysis (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 1071-1081 
    Details
    ISSN: 1572-8943
    Keywords: ferro-powders ; non-isothermal DSC ; DTA ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Mittels Thermoanalyse wurden kommerzielle, mit der Sulfattechnologie erhaltene γ-Fe2O3 Ferropulver untereinander verglichen. In Abhängigkeit von der Technologie kann jeder γ-Fe2O3-Typ durch gewisse thermische Umwandlungsfolge charakterisiert werden. Thermoanalyse und Datensystematisierung ermöglichten es, Kriterien zur Qualifizierung von γ-Fe2O3 Partikeln zu finden. Man fand, daß LKN Ferropulver mehr unausgewogene Oberflächeneigenschaften und chemische Zusammensetzungen besitzt als PERK- und GX-Ferropulver.
    Notes: Abstract Commercial γ-Fe2O3 ferro-powders obtained by the sulphate technology, have been compared by means of thermal analysis. Depending on the technology, each type of γ-F2O3 was found to be characterized by certain thermal transformation sequence. Thermal analysis and data systematisation allowed to find criteria for the qualification of γ- Fe2O3 particles. LKN ferropowders were found to have more disbalanced surface properties and chemical composition than PERK and GX ferro-powders.
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    Identification de polymeres par analyse thermique differentielle (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 1377-1389 
    Details
    ISSN: 1572-8943
    Keywords: DTA ; polymers having no melting endotherm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Mittels DTA wurden neunzehn verschiedene Polymere ohne endothermen Peak beim Schmelzen untersucht (Schaum Carbamid-Formol, PVC, Vinylpolyacetat, Vinylpolybutyral, Polymethacrylate, Polystyrol und seine Kopolymere). Die Identifizierung erfolgte in Übereinstimmung mit der unlängst beschriebenen allgemeinen Methode anhand der endothermen Zersetzung speaks und der exothermen Peaks.
    Notes: Abstract Nineteen different polymers having no melting endotherm (foam urea-formol, PVC, vinyl polyacetate, vinyl polybutyral, polymethacrylates, polystyrene and its copolymers) are studied by DTA. The identification is realized due to endothermic decomposition peak and exothermic peaks, according to the general method which has been described previously.
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    Thermal study of glass transitions in binary systems of simple hydrocarbons (1992)
    Springer
    Journal of thermal analysis and calorimetry 38 (1992), S. 1847-1860 
    Details
    ISSN: 1572-8943
    Keywords: DTA ; glass transitions ; hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Mittels DTA wurden Glasumwandlungserscheinungen von vier binären Systemen aus einfachen Kohlenwasserstoffen untersucht. Für alle Systeme wurde eine definitive Glasumwandlung beobachtet, wobei man eine monotone Beziehung zwischen der Glasumwandlungstemperatur (T g) und der Zusammensetzung (x) erhielt. Die Konzentrationsabhängigkeit vonT g wurde hinsichtlich der Entropietheorie auf der Grundlage des regulären Lösungsmodelles analysiert. Die Prognose konnte die Resultate nicht reproduzieren, nur das System (1-Buten)x(1-Penten)1−x. Diese Diskrepanz wird mit der Abweichung der Systeme von einer regulären Lösung erklärt und die zusätzliche Konfigurationsentropie Sc E wurde als Funktion der Konzentration geschätzt. Außerordentlich hohe Werte für 5c E wurden bei den Systemen (Propen)x(Propan)1−x und (Propen)x(Penten)1−x erhalten.
    Notes: Abstract Glass transition phenomena of four binary systems composed of simple hydrocarbons were studied by means of the differential thermal analysis (DTA). For all the systems, a definite glass transition was observed and a monotonous relation between the glass transition temperature (T g) and composition (x) was obtained. The composition dependence ofT g was analyzed in terms of the entropy theory based on the regular solution model. The theoretical prediction could not reproduce our results other than (1-butene)x(1-pentene)1−x system. This disagreement is considered to be due to deviations of the present systems from the regular solution, and the accompanying excess configurational entropy Sc E was estimated as a function of composition. Extraordinarily large values of S c E ? were obtained for (propene)x(propane)1−x and (propene)inx(1-pentene)1−x systems.
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    Studies on the Thermal Decomposition of Benzoic Acid and its Derivatives (1999)
    Springer
    Journal of thermal analysis and calorimetry 55 (1999), S. 995-1002 
    Details
    ISSN: 1572-8943
    Keywords: benzoic acid ; DTA ; DTG ; hydroxy- and aminobenzoic acids ; o-phthalic acid ; principal component analysis ; sulphanilic acid ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal decomposition of benzoic acid and its derivatives containing —OH, —NH2, —COOH and —SO3H functional groups as substituents in ortho, meta and (or) para position together with sulphanilic acid was investigated. The analyses were performed using derivatograph, sample mass ranged from 50 to 200 mg, heating rates from 3 to 15 K min−1 and static air atmosphere. It has been established that thermal decomposition of these aromatic acids proceeds through three common stages. In the first stage the phase transformations occur. The following two stages are due to the formation of intermediate products of the thermal decomposition and their combustion. Principal component analysis (PCA) was applied for evaluation of the results. Thanks to this method the influence of specific functional groups and their positions on the benzene ring on the thermal decomposition of the compounds under investigation was determined.
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    Phase Equilibria in the V2O5-Sb2O4 System (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 159-165 
    Details
    ISSN: 1572-8943
    Keywords: antimony tetroxide ; DTA ; phase equilibrium ; vanadium(V) oxide ; XRD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Differential thermal analysis (DTA) and X-ray powder diffraction (XRD) were used to study phase equilibria, established in air in the V2O5-Sb2O4 system up to 1000°C. It has been found that there is a new phase =SbVO5. The =SbVO5 has been prepared by two methods: by heating equimolar mixtures of V2O5 and α-Sb2O4 in air and by oxidation of the known phase of rutile type obtained in pure argon at temperatures between 550 and 650°C. Thermal decomposition of =SbVO5 in the solid state starts at 710°C giving off oxygen. The results provide a basis for constructing only a part of the phase diagram of the investigated system (up to 50.00 mol% Sb2O4).
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    Studies on the System ZnO-V2O5-Fe2O3 Reactivity of ZnFe2O4 Towards ZnV2O6 (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 205-210 
    Details
    ISSN: 1572-8943
    Keywords: DTA ; iron(III) ; reactivity ; XRD ; zinc ferrite ; zinc metavanadate ; zinc oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Studies on the reactivity of ZnFe2O4 towards ZnV2O6 revealed that in the solid state the phases interact in a molar ratio of 1:3 to form a new compound, to which the molecular formula Zn2FeV3O11 was assigned. The compound melts congruently at 825±5°C.
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    Crystallization Kinetics of Lithium Diborate Glass by DTA (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 755-761 
    Details
    ISSN: 1572-8943
    Keywords: crystallization ; DTA ; kinetics ; Kissinger plot ; lithium diborate glass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The crystallization process of Li2B4O7 in the glass of stoichiometric composition, characterized by the crystal growth of pre-existing nuclei, was analyzed kinetically by means of DTA. Because the number of pre-existing nuclei for the subsequent growth varies depending on the cooling rate of the glass-forming melt and heating rate of the as-prepared glass, a modified Kissinger plot was applied for evaluating the apparent activation energy to the crystal growth in the glass samples with three different thermal histories, i.e., the pre-annealed, slowly quenched and quickly quenched glasses. The process was characterized by the three dimensional growth of pre-existing nuclei with the apparent activation energy of ca 340 kJ mol−1.
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    Oxyreactive Thermal Analysis of Dispersed Organic Matter, Kerogen and Carbonization Products A Tool for Investigation of the Heated Rock Masses (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 917-924 
    Details
    ISSN: 1572-8943
    Keywords: coal ; DTA ; graphite ; kerogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract This paper presents the results of oxyreactive thermal analyses of organic matter in rocks, heated naturally during diagenetic to metamorphic processes. During the experiments we traced the reactions in the temperature range up to 900°C, it means from the very beginning of diagenetic transformations to the highest real temperatures acting in the Earth's crust as a solid phase. The results showed that TA could be a tool for the reconstruction of thermal regime in natural coal-bearing systems.
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    URL: http://dx.doi.org/10.1023/A:1010147315595
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    Changes of sodium and ATP affinities of the cardiac (Na,K)-ATase during and after nitric oxide deficient hypertension (1999)
    Springer
    Molecular and cellular biochemistry 202 (1999), S. 141-147 
    Details
    ISSN: 1573-4919
    Keywords: (Na,K)-ATPase ; Na+-binding site ; nitric oxide ; hypertension ; L-NAME ; cardiac sarcolemma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract In the cardiovascular system, NO is involved in the regulation of a variety of functions. Inhibition of NO synthesis induces sustained hypertension. In several models of hypertension, elevation of intracellular sodium level was documented in cardiac tissue. To assess the molecular basis of disturbances in transmembraneous transport of Na+, we studied the response of cardiac (Na,K)-ATPase to NO-deficient hypertension induced in rats by NO-synthase inhibition with 40 mg/kg/day NG-nitro-L-arginine methyl ester (L-NAME) for 4 four weeks. After 4-week administration of L-NAME, the systolic blood pressure (SBP) increased by 36%. Two weeks after terminating the treatment, the SBP recovered to control value. When activating the (Na,K)-ATPase with its substrate ATP, no changes in Km and Vmax values were observed in NO-deficient rats. During activation with Na+, the Vmax remained unchanged, however the KNa increased by 50%, indicating a profound decrease in the affinity of the Na+-binding site in NO-deficient rats. After recovery from hypertension, the activity of (Na,K)-ATPase increased, due to higher affinity of the ATP-binding site, as revealed from the lowered Km value for ATP. The KNa value for Na+ returned to control value. Inhibition of NO-synthase induced a reversible hypertension accompanied by depressed Na+-extrusion from cardiac cells as a consequence of deteriorated Na+-binding properties of the (Na,K)-ATPase. After recovery of blood pressure to control values, the extrusion of Na+ from cardiac cells was normalized, as revealed by restoration of the (Na,K)-ATPase activity. (Mol Cell Biochem 000: 000-000, 1999)
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    URL: http://dx.doi.org/10.1023/A:1007097617502
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    Role of nitric oxide in the induction of apoptosis by smokeless tobacco extract (1999)
    Springer
    Molecular and cellular biochemistry 200 (1999), S. 51-57 
    Details
    ISSN: 1573-4919
    Keywords: smokeless tobacco ; apoptosis ; nitric oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Smokeless tobacco usage is, a growing public health concern in the United States. Lesions of the oral cavity have been clearly linked to smokeless tobacco use. The objective of this study was to determine the biochemical effects of smokeless tobacco extract (STE) exposure upon hamster cheek pouch cell (HCPC-1) cultures. HCPC-1 cells were exposed to a 5 -fold dose-range of STE (0.5, 1.0 and 2.5%) over a time-course of 24-96 h. Following each exposure we measured various biochemical parameters of cell proliferation and cell death. Cell viability, cell cycle progression and S-phase DNA synthesis were measured as markers of cell proliferation. We measured lactate dehydrogenase leakage as a marker of cell membrane damage and cell death due to necrosis. No significant alterations were observed in cell cycle progression and cell proliferation as a result of exposure to STE. LDH measured colorimetrically indicated no significant effect with the lower doses (0.5, 1.0 and 2.5% STE). Apoptosis measured as the A0 peak and by the TUNEL procedure revealed that STE caused significant rates of apoptosis. Maximal apoptosis was noted between 48-96 h. In order to probe the mechanism further we measured the levels of nitrites as an indicator of nitric oxide (NO) in the media. NO levels were significantly elevated at the doses that caused an induction of apoptosis. The results from this study indicate that STE causes a dose-dependent induction of apoptosis and that this is mediated by nitric oxide.
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    URL: http://dx.doi.org/10.1023/A:1006985700851
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    Nitric oxide inhibits wound collagen synthesis (1999)
    Springer
    Molecular and cellular biochemistry 200 (1999), S. 27-33 
    Details
    ISSN: 1573-4919
    Keywords: skin ; wound ; nitric oxide ; collagen ; rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Nitric oxide (NO) is a messenger molecule which regulates many physiological functions like immunity, vascular tone and serves as a neurotransmitter. Although it is known to participate in healing process, its role in collagen synthesis is not clear. Therefore, the present investigation was done to study the role of NO in wound collagen synthesis. Rats received full thickness, circular (8 mm), transdermal wounds which were treated with NO releaser, sodium nitroprusside (SNP, 0.001 100 μM) topically for 5 days. Wound collagen content estimated in terms of hydroxyproline (HP) and confirmed histochemically was decreased significantly by all SNP doses. L-Arginine, a substrate for nitric oxide synthase (NOS) when applied topically decreased collagen content of the wounded tissues. N-Nitro-L-arginine methyl ester (L-NAME), a competitive inhibitor of NOS, increased wound collagen content significantly as compared to untreated and SNP treated animal wounds when administered intraperitoneally at the doses 3, 10 and 30 mg/kg. Furthermore, histological findings also demonstrated laying down of thick collagen bundles and proliferation of fibroblasts together with prominent angiogenesis in L-NAME treated wound tissues as compared to untreated and SNP treated tissues. N-nitro-D-arginine methyl ester, an inactive isomer, was found to have no effect on wound collagen levels. When L-arginine was administered in L-NAME pretreated rats, it significantly elevated wound HP content. The results indicate that NO plays an important role in regulating the collagen biosynthesis in skin model of a healing wound.
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    URL: http://dx.doi.org/10.1023/A:1006977513146
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    Myocardial preconditioning: Basic concepts and potential mechanisms (1999)
    Springer
    Molecular and cellular biochemistry 196 (1999), S. 3-12 
    Details
    ISSN: 1573-4919
    Keywords: ischemia ; preconditioning ; adenosine ; protein kinase C ; KATP channel ; free radicals ; heat shock proteins ; antioxidants ; nitric oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Preconditioning is a phenomenon, where brief periods of stress such as ischemia, heat shock or certain pharmacological agents make the heart tolerant to subsequent lethal ischemic injury. Preconditioning seems to involve a variety of stress signals which include activation of membrane receptors and signaling molecules such as protein kinase C, mitogen-activated protein kinases, opening of ATP-sensitive potassium channel and expression of a number of protective proteins. In this review, the potential role of these mechanisms is discussed.
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    URL: http://dx.doi.org/10.1023/A:1006949626070
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    Fever: An integrated response of the central nervous system to oxidative stress (1999)
    Springer
    Molecular and cellular biochemistry 196 (1999), S. 125-132 
    Details
    ISSN: 1573-4919
    Keywords: fever ; E. coli lipopolysaccharide ; dithiothreitol ; methylene blue ; nitric oxide ; malondialdehyde ; biothiols ; glutamate ; NMDA-receptor ; oxidative stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract Immediately after bacterial endotoxin (LPS) enters the circulatory system there is increased production of free oxygen radicals by cells of the reticulo-endothelial system, followed by the release of cytokines considered as putative endogenous pyrogens. Fever originates by central nervous system activities, but neither exogenous nor endogenous pyrogens are able to cross the blood-brain barrier and the true signal which is transmitted to structures inside the blood-brain barrier is still unknown. To study the role of oxygen radicals in fever, we pretreated rats with methylene blue, an inhibitor of superoxide and hydroxyl radical production and investigated the febrile response to LPS in conscious rats by measuring malondialdehyde formation as an index of lipid peroxidation by oxygen radicals. Methylene blue lowered resting malondialdehyde levels to near detection level and significantly suppressed its rise which was regularly found following LPS in the untreated state. Pretreatment with methylene blue completely blocked the febrile response. Since fever is a central nervous system-mediated response these results indicate that the brain is able to sense oxidative stress and vicinal thiol groups of the redox-modulatory site of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptor-channel complex could function as a possible receptive structure. To test this hypothesis we injected rabbits with the disulfide reducing agent dithiothreitol (DTT), known to penetrate the blood-brain barrier, and monitored its effect on normal and febrile body temperatures. DTT induced, independently of ambient temperature, within minutes and dose-dependently the full pattern of heat loss responses causing a fall of core temperature, indicative of a lowered thermoregulatory setpoint. Pretreatment with a bolus dose of 5 mg/kg DTT, followed by a continuous infusion of 5 mg/kg/h for 3 h completely prevented LPS-induced fever. A bolus dose of 20 mg/kg DTT, starting 30 min after LPS, immediately reversed the febrile cold defense pattern and lowered body temperature. We conclude that DTT reduces in the central nervous system oxidized vicinal thiol groups of NMDA receptors, thereby augmenting glutamate-induced nitric oxide synthase activation, and, thus, enhanced formation of NO, which, in turn, lowers the thermoregulatory setpoint. Reduction of other disulfide-containing molecules, especially oxidized glutathione and thiol-containing enzymes, by DTT by might additionally contribute to preventing fever.
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    URL: http://dx.doi.org/10.1023/A:1006936111474
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    2-Bromoacetyl-6-methoxynaphthalene: A useful fluorescent labelling reagent for HPLC analysis of carboxylic acids (1992)
    Springer
    Chromatographia 33 (1992), S. 13-18 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fatty acids and bile acids ; Fluorogenic precolumn derivatization ; 2-Bromoacetyl-6-methoxynaphthalene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The use of 2-bromoacetyl-6-methoxynaphthalene as a fluorogenic labelling reagent in pre-column derivatization for the HPLC separation of biologically active carboxylic acids (fatty acids and bile acids) has been investigated. The compound reacts (30 min. at 70°C) with carboxylic acids to give fluorescent esters that can be separated by reversedphase HPLC and detected at λ ex. 300 nm, λ em. 460 nm. The experimental conditions for the derivatization and chromatographic separation are discussed. Applications to the determination of valproic acid and chenodeoxycholic acid in pharmaceutical formulations are described.
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    URL: http://dx.doi.org/10.1007/BF02276844
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    HPLC method for the simultaneous analysis of valproic acid and other common anticonvulsant drugs in human plasma or serum (1992)
    Springer
    Chromatographia 33 (1992), S. 37-40 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Valproic acid ; Simultaneous determination of anticonvulsants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The derivatizing procedure of Moody et al. [20] for valproic acid has been simplified and applied to the simultaneous HPLC determination of valproic acid (VPA), barbital (B), primidone (PRM), phenobarbital (PB) and carbamazepine (CBZ) in serum or plasma of epileptic patients. The sample is deproteinized with acetonitrile containing esterification agents and an aliquot of the supernatant is heated to 70°C for 15 min with 4-bromophenacyl bromide. The reaction mixture is analysed on a C18 column at ambient temperature, with gradient elution and with detection at 205 nm. The time required for the chromatographic analysis is 13 min; identification is based on retention time and quantification is by peak area determination with an internal standard. The calibration curves show good linearity in the range 6.25 to 100 mg/L. The detection limits at a signal: noise ratio ≥3, ranged from 1 mg/L for B and CBZ to 2–3 mg/L for PRM, PB and VPA. The method described for the simultaneous determination of the five drugs in the same plasma pool, correlated well with isocratic HPLC methods specific for each drug. The simultaneous procedure described allows a reproducible (CVs≤6.5% within run) and rapid (25 min for sample preparation: 13 min for chromatographic run) therapeutic monitoring of patients treated with VPA and two or more antiepileptic drugs.
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    URL: http://dx.doi.org/10.1007/BF02276848
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    Porous polymer packings from vinyl ether derivatives for reversed-phase liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 19-24 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous polymer spherical packings ; Vinyl ether ; Alkali resistance ; No abnormal adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Spherical, porous-polymer particles for column packing in high-performance liquid chromatography were prepared by suspension copolymerization of alkylvinyl ether with triethyleneglycol divinyl ether. The hydrophobicity of the packings was easily adjusted by changing the monomer ratio. The packings showed the usual reversed-phase liquid chromatographic properties, but did not sho abnormal retention, tailing and broadening of peaks and irreversible adsorption of ionic and aromatic substances, owing to the lack of ionic or aromatic groups. In addition, the packings were stable in alkaline solutions because of the relative alkali stability of C−O−C bonds as compared with CO−O and Si−O−C bonds in conventional packings.
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    URL: http://dx.doi.org/10.1007/BF02276845
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    Comparison study between indirect photometric and direct conductivity detection for anion exchange chromatography using naphthalenesulfonate derivatives as mobile phases (1992)
    Springer
    Chromatographia 33 (1992), S. 25-31 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Anion exchange ; Indirect photometric and direct conductivity detection ; Naphthalenesulfonate ; Inorganic anions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Indirect photometric and unsuppressed direct conductivity detection modes are examined using naphthalene mono-, di-, and tri-sulfonate as mobile phases for the separation of several anions such as F−, Cl−, NO2 −, Br−, NO3 −, SO4=,I−, and SCN− using a commercial anion exchange column. With all three mobile phases, conductivity detection shows better sensitivities and detection limits than indirect photometry. Conductivity detection is 5 to 16 times more sensitive than indirect photometry for all analytes. Detection limits achieved using these mobile phases are, for example, 0.04 ng and 0.1 ng for chloride ion with conductivity and indirect photometry, respectively. Both detection modes give wide linear ranges extending from at least 100 ppm to the detection limit of each anion which is generally about 0.02 ppm. Sulfur oxide anions such as dithionate and tetrathionate are separated using flow programming with naphthalenetrisulfonate as the mobile phase in less than 20 minutes. With both detection modes, desired chromatographic performance of these three eluents is achieved without pH adjustment of the mobile phase.
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    URL: http://dx.doi.org/10.1007/BF02276846
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    An enhanced liquid chromatographic method for 5-hydroxymethylfurfural determination in UHT milk (1992)
    Springer
    Chromatographia 33 (1992), S. 45-48 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Heat-treated milk ; Milk quality indicators ; 5-Hydroxymethyl-2-furfuraldehyde
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An enhanced method of HPLC for the determination of 5-Hydroxymethyl-2-furfuraldehyde (HMF) in fluid milk was perfected. Its resolving capacity permitted the specific separation of this compound. The real concentration (μmol/l) of HMF was determined and not the HMF value, as in the colorimetric analysis, where an intermediary coloured compound (HMF-TBA) is utilised. The optimum pH condition (pH=4.0–4.2) for the mobile phase to prevent overlapping between the HMF peak and the peaks of the other compound (α and β) that coeluted with the HMF and also the optimum organic solvent content (3% or 7%) were established. This is a sensitive, quick and safe method for the determination of HMF in fluid milk.
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    Ion-pair reversed-phase liquid chromatography of arsenic species on polymeric styrene-divinylbenzene packed columns with an alkaline aqueous mobile phase (1992)
    Springer
    Chromatographia 33 (1992), S. 581-585 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Arsenic compounds ; Polymeric styrene divinylbenzene phase ; Ion-pairing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The resolving power of an ion-pair reversed-phase liquid chromatography method, on a polymeric stationary phase (PRP-1) with an alkaline aqueous mobile phase (pH=9) containing tetrabutylammonium cation as ion-pairing agent, is compared with a traditional ion-pairing system using an octadecyl-modified silica column and a neutral aqueous mobile phase (pH=7.3). This chromatographic system (PRP-1 column) provides a rapid means for the determination of two of the most important arsenic species, arsenobetaine and arsenite. Addition of methanol (5%) to the aqueous mobile phase allows the differentation of arsenobetaine from the system peak when using UV detection.
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    Comparison of provitamin A determination by normal-phase gravity-flow column chromatography and reversed-phase high performance liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 133-137 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gravity-flow column chromatography ; Provitamin A determination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The provitamin A content of some food samples was determined by methods involving MgO: Hyflosupercel gravityflow column chromatography (GFCC) and reversed phase high performance liquid chromatography (HPLC), the quantitation being done by external standardization (HPLC-ES) or internal standardization (HPLC-IS) with Sudan. The results obtained with α- and β-carotene in carrots, β-carotene and β-cryptoxanthin in papaya and β-carotene in tomato and kale agreed well, showing that any of the these techniques can be used, provided the analysis is done under optimum conditions. Good separation of the different provitamins using GFCC depends on the analyst's skill and visual acuity. HPLC-ES required a constant supply of provitamin standards, thus the varying purity of commercially available standards and the high instability of these compounds could pose grave problems. Due to the stability of Sudan, HPLC-IS appeared to be the method of choice although passage of the extract through a MgO: Hyflosupercel minicolumn was required prior to injection to separate chlorophylls, dihydroxy- and polyoxycarotenoids which would otherwise elute with Sudan. Nonconformity of the Sudan structure to those of the provitamins did not effect the quantitative results. The chromatographic separation, identity and quantification of the provitamins could be more easily established by using HPLC-IS, complemented with GFCC.
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    Diastereoselective and enantioselective chromatography of the pyrethroid insecticides allethrin and cypermethrin (1992)
    Springer
    Chromatographia 33 (1992), S. 103-112 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Gas chromatography ; Chiral separations ; Allethrin ; Cypermethrin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Liquid and gas chromatographic separations of the pyrethroid insecticides allethrin and cypermethrin have been investigated with various achiral and chiral stationary phases. Diastercomeric and enantiomeric selectivity was observed for cypermethrin on a Pirkle-type chiral LC stationary phase, but very strong interactions and therefore long retention times prevented the separation of allethrin on this phase. Trans-allethrin isomers were separated on a chiral β-cyclodextrin RP-HPLC column while cypermethrin showed some difficulties on this phase due to isomerization. Diastereomeric but no enantiomeric selectivity by GC was achieved for cypermethrin with an apolar DB 5 capillary. GC separation of the diastereomers was used to study the selective photodegradation of cypermethrin isomers after forestry applications. Chiral β-cyclodextrin-based GC phases showed some enantioselectivity for cis- and trans-allethrin isomers. A separation of the eight isomers into six partially resolved peaks was achieved by GC with a coupled column consisting of chiral permethylated β-cyclodextrin and DB 1701 as stationary phases. This combination was used to characterize allethrin formulations intended for indoor use and to investigate allethrin products formed by ozonolysis of thin films of the insecticide.
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    Estimation of diuretic drugs in biological fluids by HPLC (1992)
    Springer
    Chromatographia 33 (1992), S. 177-185 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diuretics ; Screening and determination of diuretics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary This critical review of different methods proposed for the determination and screening of diuretics is directed mainly, because of its potential application, towards highperformance liquid chromatography.
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    URL: http://dx.doi.org/10.1007/BF02275902
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    Peak recognition technique by a computer program copying the human judgement (1992)
    Springer
    Chromatographia 33 (1992), S. 218-224 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Peak ; Pattern recognition ; Prediction interval
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary It is still difficult to determine peaks and peak boundaries properly, though peak recognition is very important for the precision of quantitative data. A new computer program overcomes these problems using a method which is adapted from human judgements. The algorithm was developed for HPLC but can also be used in other fields of analytical chemistry.
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    URL: http://dx.doi.org/10.1007/BF02276186
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    High performance liquid chromatography of raw sugars and polyols using bonded silica gels (1992)
    Springer
    Chromatographia 33 (1992), S. 325-330 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Diol silica gels ; Carbohydrates ; Evaporative light scattering detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Bonded silica columns have been evaluated for their ability to separate carbohydrates and polyols. Mobile phases consisting of dichloromethane/methanol produced the best separations in comparison with the acetonitrile/water mixtures commonly used with amino columns. Of all the bonded phases tested, LiChrospher Diol silica provided the best separations, and selectivities were not very different from those obtained on the most popular system using an amino bonded phase and acetonitrile/water as eluent. In addition, diol columns with a dichloromethane/methanol eluent offer excellent stability with no Schiff’s base formation of reducing sugars. Using an evaporative light scattering detector, low limit detection is obtainable (20 ng of glucose from a column) and gradient elution is quite feasible.
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    Retention of some ring-substituted aniline derivatives by porous graphitized carbon. Dependence on physico-chemical parameters (1992)
    Springer
    Chromatographia 33 (1992), S. 356-360 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous graphitized carbon ; Ring-substituted aniline derivatives ; Electronic interactions ; Principal component analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention characteristics of 22 aniline derivatives were determined on a porous, graphitized-carbon column in unbuffered acetonitrile-water and methanol-water mixtures. Each aniline derivative gave symmetrical peaks in each eluent without buffers. Good linear correlations were found between the log k′ and the concentration of the organic component in the eluent. The slope and intercept values differed according to the type of organic modifier and the charcter, number and position of substituents, indicating the different selectivities of methanol and acetonitrile and the good separating power of the column. Multivariate mathematical-statistical calculations proved that the retention of ring-substituted aniline derivatives is mainly governed by electronic parameters and the hydrogen acceptor capacity of substituents.
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    Determination of furosine in milk samples by ion-pair reversed phase liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 374-376 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Ion-pairing ; Furosine ; Pyridosine ; Milk
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An ion-pair, reversed-phase, liquid chromatographic procedure using UV detection for quantitation of furosine is described. The standard plot was linear (r〉0.999) over a 5 ng range. An authentic synthesised sample of furosine was used for calibration. Commerical milk samples were analyzed by the described procedure.
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    Optimisation of data handling and detection conditions for automated chromatographic assay software (1992)
    Springer
    Chromatographia 33 (1992), S. 361-368 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Automated peak detection ; Discrete Fourier transform ; Frequency acquisition and filtering ; Peak detection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The principle of automated chromatographic peak detection and analysis software is summarized, and critical steps are systematically studied. As the only parameter to be entered is the acquisition frequency, evaluation of its effect on software performance is discussed. In the case of relatively noisy chromatograms, it is shown experimentally that numerous points per peak have to be taken, leading to quite fast computer acquisition procedures. The use of discrete Fourier transform filtration techniques can modify peak shapes and a comparative study evaluates the relative errors induced in the shapes and characteristics of the chromatographic profiles. Optimisation of filtering conditions is achieved and it is shown that for a filter position only 2% of the Nyquist frequency no deformation occurs in the chromatographic profile. Detection of the start and finish of chromatographic peaks is optimized according to a simple four step iterative procedure. In the case of simulations, the difference between the values used to simulate peaks and those calculated by the software are less than 1%.
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    URL: http://dx.doi.org/10.1007/BF02275919
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    Simultaneous determination of 5′-deoxy-5-fluorouridine, 5-fluorouracil and its main metabolites in body fluids by HPLC (1992)
    Springer
    Chromatographia 33 (1992), S. 413-417 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Fluoropyrimidine drugs ; Pharmacokinetics of doxifluridine ; Chemotherapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A reversed phase high performance liquid chromatographic method has been developed for the simultaneous determination of the pro-drug 5′-deoxy-5-fluorouridine (5′-dFUR), its metabolite 5-fluorouracil (5-FU) and some fluorinated pyrimidines involved in the metabolic activation process of 5-FU. The method has been used to monitor the bioavailability of 5′-dFUR and 5-FU in patients undergoing anticancer chemotherapy. Serum sample treatment involves addition of internal standard (5-bromouracil), protein precipitation with saturated ammonium sulphate solution and liquid-liquid extraction with ethyl acetate-isopropanol (90 ∶ 10 v/v). Urine is simply diluted with mobile phase and injected. The average recovery from serum (at 0.5 μg/mL level) was 95.0%±1.4 for 5′-dFUR and 86.3%±3.5 for 5-FU. A linear response extending over four decades of concentration was observed. Detection limits in the low ng/ mL range were obtained using a 250 μL sample size and a 20 μL injection volume. Within-day and between-day coefficients of variation were below 4 and 10%, respectively.
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    URL: http://dx.doi.org/10.1007/BF02262320
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    Total and individual determination of carbamate pesticides by use of an integrated flow-injection/HPLC system (1992)
    Springer
    Chromatographia 33 (1992), S. 449-453 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Flow injection analysis ; Combined flow injection/HPLC ; Carbamate pesticides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An integrated flow injection (FI)/HPLC system for the total and individual determination of carbamate pesticides (propoxur, carbofuran and carbaryl) is proposed. The determination is based on the alkaline hydrolysis of the analytes and subsequent coupling with diazotized sulphanilic acid to yield the monitored dyes with or without a prior separation step by HPLC in a C18 column. The calibration curves obtained are linear in the μg/ml range and r.s.d. values are between 0.5 and 3.7% in all instances. Injection of the sample into the FI manifold allows the total pesticide content in the sample to be screened. The manifold thus acts as a post-column reactor/detector of the chromatograph for samples with high overall carbamate content, which are also injected into the HPLC instrument. The performance was checked with contaminated water samples.
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    URL: http://dx.doi.org/10.1007/BF02262326
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    Evaluation of the enantioselectivity towards β-blocking agents of the α1 glycoprotein type chiral stationary phase: Chiral AGP®glycoprotein type chiral stationary phase: Chiral AGP® (1992)
    Springer
    Chromatographia 33 (1992), S. 454-462 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; α1 glycoprotein ; Enantioseparation ; β-blocking agents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The enantioselectivity of the α1 glycoprotein chiral stationary phase, Chiral AGP® has been evaluated for a number of β-blocking agents. A correlation has been found between the retention behaviour on this stationary phase and the hydrophobicity of the compounds. The separation factor α is higher for compounds that are well retained. Retention, and thus α, are also controlled by pH and the percentage of organic modifier in the mobile phase.
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    Isocratic HPLC separation of aromatic hydrocarbons and fluorine-containing compounds using perfluoroalkyl polymer packings (1992)
    Springer
    Chromatographia 33 (1992), S. 473-477 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Perfluoroalkylated polymer-gel packings ; Aromatic and fluorine-containing compounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Porous, perfluoroalkylated polymer-gels for column packings in high-performance liquid chromatography (HPLC) were prepared by suspension polymerization of heptadecafluorodecyl arcylate and ethylene glycol dimethacrylate. The packings showed no abnormal retention for ionic or aromatic compounds, due to the lack of ionic or aromatic groups. In addition, the packings showed no excessive retention for strongly hydrophobic compounds which is often the case with long-chain, alkylated silica gels and polymer gels. This is due to the extremely low surface energy of perfluoroalkyl groups. Therefore, perfluoroalkylated polymer gels enable isocratic HPLC separation of solutes with significantly different hydrophobicity.
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    URL: http://dx.doi.org/10.1007/BF02262330
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    Comments on the paper “correlation between retention in liquid chromatography and the adsorption energy” by J. Kloubek (1992)
    Springer
    Chromatographia 33 (1992), S. 485-486 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous glass ; Surface free energy ; Film pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
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    URL: http://dx.doi.org/10.1007/BF02262332
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    Correlation between retention in liquid chromatography and the adsorption energy (1992)
    Springer
    Chromatographia 33 (1992), S. 478-484 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Porous glass adsorbents ; Surface free energy ; Oriented adsorption of hydrocarbons
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The relationship between the specific capacity factor (k/S, where k is the capacity and S is the surface area of the sorbent, in m2) in the liquid chromatography of aromatic hydrocarbons and the adsorption energy (-°GA) has been investigated. The previously published results, based on the calculation of the work of adhesion (WSA) from contact angles, were re-examined and a new hypothesis on interactions at interfaces was employed. Direct proportionality has been found between k/S and-°GA, which allows prediction of the chromatographic behavior of adsorbates on sorbents. The surface free energy components were calculated in order to determine-°GA in terms of the work of adhesion. The dispersion component of the surface free energy of glass was obtained from the adsorption isotherm of n-octane and it was found that the hydrocarbon molecules are adsorbed in an oriented position. The contact angles of liquids on the outer surface of porous solids do not yield reliable values of WSA and of the surface free energy components. A higher intermolecular attraction increases WSA and decreases the contact angle in pores.
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    A high-performance liquid chromatographic method for the analysis of adenosine and some metabolites in the brain tissue of rats (1992)
    Springer
    Chromatographia 34 (1992), S. 563-567 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Adenosine and some metabolites ; Extraction from brain tissue ; Quantitative determination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An analytical procedure has been developed for the assay of adenosine and some metabolites in brain tissue extracts of rats. This paper reports the extraction method, the technique adopted to avoid enzymatic transformations and the chromatographic conditions for the identification and quantitation of these nucleosides and bases. Peaks in the chromatograms of brain tissue extracts were identified by retention times, absorbance ratios of reference compounds and by enzymatic peak-shift.
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    Influence of silica gel surface purity on the coverage density of chemically bonded phases (1992)
    Springer
    Chromatographia 34 (1992), S. 573-580 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Chemically bonded phases (CBP) ; Surface heterogenity ; Surface purification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The surface chemistry of eight silica-gels with different siliceous matrix structures have been described. The influence of surface impurities on the chemical modification process (coverage density) with monooctadecylsilane has been studied. The surfaces of the adsorbents, before chemical modification, were cleaned by extraction with 20% HCl. Bare and modified materials were characterized using different physico-chemical methods e.g.: SIMS, CP/MAS NMR, porosimetry, pH measurement, elemental analysis and chromatography (GC & HPLC). The presence of trace amounts of different metallic elements creating new adsorption centers on the surfaces of the packings, have been demonstrated. Moreover, it has been shown that washing of silica gel adsorbents increases the coverage density of alkylsilyl ligands and improves the chromatographic properties of prepared packings.
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    URL: http://dx.doi.org/10.1007/BF02269866
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    Zone electrophoretic sample treatment coupled on-line with column liquid chromatography for the determination of basic and acidic compounds in biological samples (1992)
    Springer
    Chromatographia 34 (1992), S. 581-588 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Zone-electrophoretic sample treatment ; Basic and acidic compounds ; Biological samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A modified valve arrangement for zone-electrophoretic sample treatment (ZEST)-which is coupled on-line with column liquid chromatography — is used to pretreat biological (plasma) samples. Carry-over of plasma proteins depends on the pH of the electrophoresis buffer. The determination of propranolol, metoprolol, cromolyn and salicylic acid demonstrates that both basic and acidic analytes can be isolated from the plasma matrix with high selectivity. Analogous piperazines, with different protein binding properties, were used to study the influence of protein binding on the recovery. It is shown that high protein can cause a decreased recovery.
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    HPLC analysis of the main oxindole alkaloids fromUncaria tomentosa (1992)
    Springer
    Chromatographia 34 (1992), S. 597-600 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Oxindole alkaloids ; Uncaria tomentosa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The main oxindole alkaloids from the root bark ofUncaria tomentosa were separated by reversed phase HPLC with an acetonitrile/methanol/phosphate buffer solvent gradient. UV detection was carried out at 245 nm. The chromatographic parameters for the separation of the alkaloids were optimized by studying the impact of the pH value of the mobile phase and the column temperature on the separation efficiency of the analytical system. The best separation was achieved with a mobile phase pH of 6.6 and a column temperature of 15°C. The method developed is suitable for the qualitative characterisation and quantitative determination of oxindole alkaloids in crudeUncaria tomentosa extracts and phytopharmaceuticals.
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    Indirect stereoselective determination of enantiomers of furprofen in human plasma by high-performance liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 618-620 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Enantiomers of furprofen ; Human plasma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A sensitive and stereoselective liquid chromatographic (HPLC) assay for the S and R enantiomers of furprofen in human plasma has been developed. The assay is based on derivatization with S(−)-1-phenylethylamine with formation of two diastereoisomeric derivatives and on their separation and quantitation using HPLC with uv detection. The method is linear from 25 to 600 ng ml−1 of both enantiomers, with a variation coefficient below 10.8%, and a detection limit of 20 ng ml−1. This procedure is suitable for pharmacokinetic studies.
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    Solute-micelle association constants and correlation of octanol-water coefficients with hydrophobicity for polycyclic aromatic hydrocarbons by micellar chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 627-635 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Micelle-solute association constants ; Polynuclear aromatic hydrocarbons ; Octanol/water partition coefficients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Sodium dodecyl sulphate, hexadecyltrimethylammonium bromide and polyoxyethylene(23) lauryl ether were investigated as mobile phases in the micellar liquid chromatography of polycyclic aromatic hydrocarbons of environmental concern. A wide range of surfactant concentrations were used and the retention parameters and distribution coefficients calculated. The trends in the retention data for the PAHs are discussed and several conclusions are presented concerning the partition coefficients when these surfactants are present in the mobile phase. Comparisons are made between the structural features of the compounds and their capacity factors, and the octanol/water partition coefficients are correlated with hydrophobicity for the PAHs studied.
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    Retention characteristics of chlorinated polycyclic aromatic hydrocarbons in normal phase HPLC. II. Chloro-substituted PAHs (1992)
    Springer
    Chromatographia 34 (1992), S. 115-120 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Normal phase separations ; Chloro-substituted polycyclic aromatic hydrocarbons ; Coupled column system ; Environmental samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention behaviour of chloro-substituted PAHs on several commercial normal bonded phase HPLC columns has been investigated. Chloro-substitution was shown to generally decrease the retention on stationary phases like amino-, diol- and nitrophenylpropyl-modified silica. Dimethylaminosilica exhibited more complex retention characteristics towards chloro-substituted PAHs. On this stationary phase, the position of the chlorine substituents on the aromatic solute seemed to be of greater importance for retention than on the amino-, nitro- and diolsilica. For some chloro-PAHs, the retention was shown to increase with the number of chloro-substitutions, probably due to the large affinity of the electron-rich nitrogen in the stationary phase for the electron deficient π-system of the chloro-PAHs. Chloro-substituted PAHs were strongly retarded on the electron donating 2-(1-pyrenyl)-ethylsilica (PYE) stationary phase. However, the molecular shape of the chloro-derivatives had a large influence on retention, which was considerably decreased for some nonplanar chloro-derivatives of chrysene and benz(a)anthracene. A two-dimensional back-flush HPLC method, consisting of a combination of a nitrophenylsilica column and a PYE column of matched lengths, was shown to be useful for clean-up of chloro-substituted PAHs in environmental samples.
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    A column switching technique for the determination of lidocaine and its metabolites in horse urine (1992)
    Springer
    Chromatographia 34 (1992), S. 143-145 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Column switching ; Lidocaine ; Horse urine analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A rapid method is described for the determination of lidocaine and its metabolites in horse urine using a column switching technique and HPLC analysis. This procedure offers a sensitive assay without the need for time consuming extractions.
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    URL: http://dx.doi.org/10.1007/BF02276127
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    Cystine and cysteine analysis as the same phenylthiocarbamyl derivatives by HPLC in protein hydrolyzates (1992)
    Springer
    Chromatographia 34 (1992), S. 132-136 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Cysteine, cystine ; Phenylthiocarbamyl derivatives ; Protein hydrolyzates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A new approach is described, and a novel explanation presented, for the high performance liquid chromatographic analysis of cystine and cysteine as their phenylthiocarbamyl derivatives. PTC cystine and cysteine have been eluted with the same retention times and molar responses, most probably due to electrophilic attack of phenylisothiocyanate on cystine resulting in the scission of the disulfide bond yielding two moles of cysteine. Further, total PTC cystine and cysteine have been measured both in model solutions and in standard protein hydrolyzates (lysozyme, bovine albumin, ribonuclease) with the same linearity as the other ineteen amino acids. The reproducibility of the measurements, at the 250–750 pmole level, proved to be 4.1% (Relative Standard Deviation %) or less.
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    Retention behaviour of crown ethers and actinomycin D in reversed-phase HPLC (1992)
    Springer
    Chromatographia 34 (1992), S. 155-158 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Retention ; Crown ethers ; Actinomycin D ; Metal cation complexation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention of crown ethers in reverse-phase HPLC has been determined by their bonding ability with cations present in the eluent. The dependence of retention of crown ethers on cation concentration exhibits an inflection and makes it possible to calculate stability constant for the crown ether-cation complex. It is shown that in 75% MeOH retention of antitumor antibiotic, actinomycin D, depends on [Na+] and not on [K+] at concentrations of K+ from 5×10−7 to 10−1 mol l−1. Hence, actinomycin D may be classified as an ionophore-antibiotic.
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    Liquid chromatographic retention and separation of phenols and related aromatic compounds on reversed phase columns (1992)
    Springer
    Chromatographia 34 (1992), S. 146-154 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Phenolic compounds ; Optimisation of isocratic separations ; River water samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Isocratic column liquid chromatographic systems with UV absorbance detection at 280 nm have been developed for the separation of 29 phenolics and related compounds. The selectivity was investigated on silica-, carbon- and polymer-based separation columns for the separation of phenolic type of components. The effects of various acetonitrile/buffer mixtures, and pH of the mobile phase, and their impact on the retention of the phenols was assessed. Tables of retention times on the four columns for the 29 phenols with two different acetonitrile/buffer mixtures, together with the retention times at three pHs from 6.5 to 2.3 with varying levels of organic modifier on the LiChrospher RP 18 column are presented. As an application, the analysis of real river water samples from the Ebro river is described using a solid phase extraction step prior to injection into the chromatographic system.
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    Microcolumn liquid chromatography on carbon sorbents (1992)
    Springer
    Chromatographia 34 (1992), S. 173-176 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carbon packing materials ; Aromatic compound separation ; Eluent effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention volume dependences on the molar volume were found for aromatic compounds using liquid microcolumn chromatography. The contributions of the functional groups in molecules of these compounds to the total retention value were calculated from the capacity factor values. The comparison of capacity factor values for carbon sorbents and octadecyl-silicagel has shown that for several microcolumn separations the carbon sorbent column has a better selectivity and resolution than the octadecyl-silicagel column.
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    Synthesis of acceptor bonded phases for donor-acceptor liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 177-181 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Synthesis of bonded stationary phases ; Acceptor ligands ; Normal phases ; PAHs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The synthesis of several electron-acceptor stationary phases has been reviewed the materials evaluated for their capacity to separate polyaromatic hydrocarbons (PAHs). Chemically bonded phases were obtained by the same procedure; the organosilane moiety is monofunctional and the HPLC behaviour is compared under identical conditions. Examples of PAHs separations are given.
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    Silanol group effect in C18 bonded phases in HPLC (1992)
    Springer
    Chromatographia 34 (1992), S. 182-184 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; C18 bonded phase ; Residual silanol groups ; Metal 5-Br-PADAP complexes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary If any residual (free) silanol groups remain at the surface of silica gel after bonding treatment, they may affect the retention of solutes since the dissociated groups (≡SiO−) will attract cations. The silanol group effect on the retention of cationic solutes will increase with increasing pH of the mobile phase but the effect will decrease with increasing hydrophobic-ion concentration at the C18 surface because such ions can mask the residual silanol groups. A method for the separation of metal complexes with 2-(5-bromo-2-pyridylazo)-diethylaminephenol (5-Br-PADAP) has been developed. The hydrophobic ion in the MeOH/H2O mobile phase was tetrabutylammonium (TBA).
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    Michael Tswett's columns: Facts and speculations (1992)
    Springer
    Chromatographia 34 (1992), S. 342-346 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; History of chromatography ; Calcium carbonate stationary phase ; Chlorophyll
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Although Michael Tswett is the originator of chromatography, little is known about the performance of his chromatographic systems. His descriptions of the separation of plant pigments are detailed but nevertheless difficult to interprete by today's chromatographic theory. By our own experiments with the system calcium carbonate/benzene it was found that the separation factor of chlorophyll a and b is approx. 1.6 which means that less than 100 theoretical plates are necessary for separation. Tswett's columns with 50 μm particles and 2–3 cm of bed height presumably exceeded this plate number. His separations could have been impaired by mass overload and by a volume flow rate which was two orders of magnitude faster than the optimum.
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    Factors influencing retention and resolution of substituted alkylbenzenes in reversed-phase liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 347-356 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Isomeric substituted alkylbenzenes ; Retention and resolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The retention data of isomeric xylenes, ethyltoluenes and diethylbenzenes, and of mesitylene, benzene, toluene and ethylbenzene were obtained on a reversedphase column using methanol-water and ethanol-water mobile phases at four different temperatures. This database was used to relate the dependence of solute retention and resolution on the polarity of the mobile phase, solute dipole moment, and column temperature. The additivity of the free energy of the transfer of solute molecules or solute segments from the stationary phase to the mobile phase, was examined for the isomeric compounds. For this, the logarithm of the net retention volume was substituted for the free energy. Deviations from the additivity of free energies indicate that the separation of isomeric substituted alkylbenzenes is governed by their differential interactions with both the polar mobile phase and nonpolar stationary phase. Among the disubstituted alkylbenzenes,ortho-isomers favor the mobile phase more andpara-isomers tend to prefer the stationary phase more. Themeta-isomers are found to follow the additivity rule closely. These trends are amplified as the polarity of the mobile phase is increased indicating that these isomers are resolved better in water-rich mobile phases. These findings are substantiated by analogous results from gas-liquid chromatographic retention data, estimation of dipole moment effects, and examination of the entropic and enthalpic contributions to the net retention volume.
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    Direct determination of Benzo[a]pyrene in oil distillates by on-line two-dimensional HPLC with column switching (1992)
    Springer
    Chromatographia 34 (1992), S. 376-380 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Column switching ; Polycyclic aromatics ; Oil distillates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A selective and sensitive HPLC method for the determination of Benzo[a]pyrene (B[a]p) in oil fractions by means of column switching is described. The diluted oil samples were injected directly onto a silica column with isooctane as eluent. After fast elution of the main part of the sample matrix, the B[a]p containing fraction was transferred on-line to a dinitro-aryl-modified silica column for final separation with isooctane/tetrahydrofuran. A detection limit of 50 ppt B[a]p was found when using fluorescence detection.
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    Gradient high performance liquid chromatography of block copolymers of styrene andt-butyl methacrylate II. Association phenomena in mixtures of block copolymer with polystyrene (1992)
    Springer
    Chromatographia 34 (1992), S. 363-368 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Precipitation chromatography of polymers ; Block copolymers of styrene-butyl methacrylate ; Association phenomena
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Block copolymers of styrene andt-butyl methacrylate can be analysed by methanol/tetrahydrofuran gradients on C18 or phenyl bonded phase columns. On both of these columns, retention increases with styrene content of the samples. At 50°C, the retention of PS or a block copolymer containing 45% styrene was longer on the phenyl than the C18 columns. This indicates the contribution of adsorption to retention on phenyl bonded phase columns. Lowering the temperature from 50 to 30°C caused earlier elution of part of the sample from the phenyl phase. On a C18 phase the same drop in temperature improved the shape of the peak, which also started later than at 50°C. This effect of temperature is generally observed in polymer retention due to an adsorption mechanism, whereas increasing retention with decrease in temperature is characteristic of a precipitation mechanism. The block copolymer investigated contained 15% free polystyrene precursor which could not be separated from the block copolymer under the conditions employed. The addition of 20% PS homopolymer with a molecular weight similar to that of the styrene block in the copolymer showed that the polystyrene eluted together with the block copolymer, whereas the addition of PS homopolymer with a much higher molecular weight caused an extra peak at the expected elution time.
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    Multidentate phenyl-bonded phases in high-performance liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 381-385 
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    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Molecular recognition ; Multidentate phenyl-bonded phases ; PAHs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary New multidentate phenyl-bonded phases (MPBPs) were synthesized and evaluated the chromatographic retention behaviour with polycyclic aromatic hydrocarbons as sample probes in high-performance liquid chromatography. The new MPBPs show different retention characteristics from the previously synthesized MPBP, designated TP. Nevertheless, the results indicate that the retention mechanism is still the same as the TP phase: the size and shape of the solute molecule can be recognized by a cavity-like space formed by the methyl groups and phenyl rings of MPBPs.
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    URL: http://dx.doi.org/10.1007/BF02268372
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    Comparison and evaluation of HIC columns of different hydrophobicity (1992)
    Springer
    Chromatographia 34 (1992), S. 391-397 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Hydrophobic interaction ; Stationary phases ; Salt effect ; Proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Retention and selectivity in hydrophobic interaction chromatography (HIC) depend both on the type of stationary phase and on the mobile phase. In the last few years various high performance packing materials and columns have been introduced for HIC resulting in a range of different retentions and selectivity. We have investigated the effect of the stationary phase on the retention of various proteins. The retention of some solutes of different hydrophobicities were measured on three commercial HIC columns (TSK-Phenyl, Synchropack-Propyl, CAA-HIC) under isocratic conditions using water-methanol mixtures as eluent. The log kw values determined according to the literature were devalues determined according to the literature were dependent on the type and structure of the stationary phase and indicated a much less hydrophobic character for these columns than that obtained for reversed phase columns. Gradient separations were then carried out on a standard protein mixture using ammonium sulfate and sodium citrate to change the gradient time. In order to compare the effect of the stationary phase and the two salts investigated apparent capacity factors (kg) were determined and plotted against the gradient time obtained for the three columns in the two eluent system. It was shown that the type of stationary phase had a significant effect on the retention of proteins. In addition, the effect of the mobile phase composition, i.e. salt type, was considerably different on the various stationary phases. In order to exploit the potential of HIC to modulate selectivity for the separation of proteins, the combined effect of the stationary phase and the type of salt should be taken into account.
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    URL: http://dx.doi.org/10.1007/BF02268374
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    Chromatographic characteristics of porphyrine ether glycerides (1992)
    Springer
    Chromatographia 34 (1992), S. 431-432 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Thin-layer chromatography ; Porphyrine ether glycerides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Efficient TLC and HPLC conditions for the separation of a newly synthesized class of compounds, porphyrine ether glycerides, have been established. Supplementary physico-chemical characteristics are given for this group of solutes.
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    URL: http://dx.doi.org/10.1007/BF02268379
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    Integrated FIA/HPLC method for preconcentration and determination of transition metal ions (1992)
    Springer
    Chromatographia 34 (1992), S. 445-449 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Flow injection analysis ; Combined methods ; Transition metal ions ; Aqueous samples
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An automatic method based on the combination of a flow injection (FI) manifold with a liquid chromatograph has been developed for the enrichment and determination of transition metal ions in water samples. Alternatively, the FI configuration can be used as a screening system for the determination of the total concentration of heavy metals. Two-parameter expressions for calibration graphs involving preconcentration time and concentration of the analytes were established for both the FIA and the integrated FIA/HPLC methods. The preconcentration time depends on the concentration level of the analytes in the samples. The method is linear in the range 2–200 ng/ml, with r.s.d. values between 1.5 and 5.0. It has been applied to the determination of copper, lead, zinc, nickel, cobalt, cadmium and manganese in synthetic water samples.
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    URL: http://dx.doi.org/10.1007/BF02290233
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    Comparison of HPLC and solid phase clean-up methods for identification of PCBs in cod-liver oil by HRGC/MS-SIM technique (1992)
    Springer
    Chromatographia 34 (1992), S. 421-430 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Solid phase extraction ; PCBs in cod-liver oil ; GC/MS identification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A group of non-planar PCBs (IUPAC nos. 28, 52, 101, 118, 138, 153, and 180) was identified in a cod-liver oil product by using high resolution gas chromatography-mass spectrometry (HRGC/MS) in electron impact (EI) and negative chemical ionization (NCI) modes. The cod-liver oil samples were prepared either in a cyano column by high performance liquid chromatography (HPLC) or by a solid phase extraction (SPE) clean-up procedure that included e.g. purified charcoal treatment. The two methods of sample preparation were evaluated on the basis of the detectabilities of the congeners. The GC/MS-SIM method allowed quantitative monitoring of congeners nos. 52, 101, 118, 138, 153, and 180 at low concentration levels. Detection limits were 1.2 pg and 130 fg (m/z 292.00) in EI and NCI modes, respectively. The determination levels in EI and NCI were 1.8 pg and 290 fg in HPLC followed by HRGC/MS and 170 pg and 27 pg in SPE followed by HRGC/MS. The linear range was from 5.0 pg/μl to 1.0 ng/μl and from 1.0 pg/μl to 1.0 ng/μl in EI and NCI modes, respectively. In addition, the co-planar PCBs, PCDDs, and PCDFs were also screened and two of the chlorinated furanes were identified by HRGC/MS-NCI after separation from non-planar PCBs by SPE. In this case the only congeners that could be quantified were 2,3,4,7,8-PCDF and 1,2,3,4,6,7,8-HCDF, the detection limit for them being 740 fg (m/z 351.90) with NCI. SPE allows the separation of the planar and non-planar compounds, but LC separation is more effective for separation of the compounds of interest from the matrix. LC clean-up is easier and faster to perform than SPE clean-up.
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    URL: http://dx.doi.org/10.1007/BF02268378
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    Separation of stereoisomers of tetramethylcalix[4]arenoctol and derivatives by high-performance liquid chromatography (1992)
    Springer
    Chromatographia 34 (1992), S. 453-456 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Calix[4]arenes ; Host-guest chemistry ; Separation of stereoisomers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A high performance liquid chromatographic procedure on 5 μm RP-18 was developed for the separation of the four possible cis-trans isomers of tetramethyl-calix[4]arenoctol, and of their octaacetates, and their octamethyl ethers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02290235
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    HPLC separation of molecular species of intact sphingomyelin, utilizing multivariate design and optimization (1992)
    Springer
    Chromatographia 34 (1992), S. 529-533 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Sphingomyelin ; Molecular species separation ; Experimental design and optimization ; Chemometrics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary An improved method has been developed for the separation of molecular species of intact sphingomyelins from natural sources (chicken egg yolk, bovine brain, and bovine milk) by high performance liquid chromatography with light-scattering detection. The method was developed and optimized using a novel multivariate optimization strategy.
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    URL: http://dx.doi.org/10.1007/BF02290247
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    High-performance liquid chromatography of carbohydrates in enzymic hydrolysate of waste paper (1992)
    Springer
    Chromatographia 34 (1992), S. 534-536 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Carbohydrates ; Enzymic hydrolysate ; Waste paper
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Waste paper was pretreated with 5M sulfuric acid at 28°C to give a gel-like solution which was then hydrolyzed with cellulase, purified fromTrichoderma viride, to form carbohydrates. The determination of the carbohydrates was accomplished using an aminopropylbonded silica HPLC column and an RI detector. The detection limits were 20 ppm; xylose, glucose, and cellobiose were the major components. Salts from the buffer solution may affect the activity of cellulase. The analysis of carbohydrates can be performed under acid conditions. HPLC analysis of carbohydrates from enzymatic hydrolysis is reliable and successful.
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    URL: http://dx.doi.org/10.1007/BF02290248
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    Nitric Oxide: A Unique Endogenous Signaling Molecule in Vascular Biology (1999)
    Springer
    Bioscience reports 19 (1999), S. 51-71 
    Details
    ISSN: 1573-4935
    Keywords: Cell signaling ; nitric oxide ; vasculation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The properties of nitric oxide as an endogenous cell signaling molecule in vascular biology are described.
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    URL: http://dx.doi.org/10.1023/A:1020150124721
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    Discovery of Some of the Biological Effects of Nitric Oxide and its Role in Cell Signaling (1999)
    Springer
    Bioscience reports 19 (1999), S. 133-154 
    Details
    ISSN: 1573-4935
    Keywords: Cell signalling ; nitric oxide ; vasculature
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The role of nitric oxide in cellular signaling in the past 22 years has become one of the most rapidly growing areas in biology with more than 20,000 publications to date. Nitric oxide is a gas and free radical with an unshared electron that can regulate an ever-growing list of biological processes. In many instances nitric oxide mediates its biological effects by activating guanylyl cyclase and increasing cyclic GMP synthesis from GTP. However, the list of effects of nitric oxide that are independent of cyclic GMP is also growing at a rapid rate. For example, nitric oxide can interact with transition metals such as iron, thiol groups, other free radicals, oxygen, superoxide anion, unsaturated fatty acids and other molecules. Some of these reactions result in the oxidation of nitric oxide to nitrite and nitrate to terminate its effect, while other reactions can lead to altered protein structure, function, and/or catalytic capacity. These diverse effects of nitric oxide that are either cyclic GMP dependent or independent can alter and regulate important physiological and biochemical events in cell regulation and function. Nitric oxide can function as an intracellular messenger, an autacoid, a paracrine substance, a neurotransmitter, or as a hormone that can be carried to distant sites for effects. Thus, it is a unique simple molecule with an array of signaling functions. However, as with any messenger molecule, there can be too little or too much of the substance and pathological events result. Some of the methods to regulate either nitric oxide formation, metabolism, or function have been in clinical use for more than a century as with the use of organic nitrates and nitroglycerin in angina pectoris that was initiated in the 1870's. Current and future research with nitric oxide and cyclic GMP will undoubtedly expand the clinicians' therapeutic armamentarium to manage a number of important diseases by perturbing nitric oxide and cyclic GMP formation and metabolism. Such promise and expectations have obviously fueled the interests in these signaling molecules for a growing list of potential therapeutic applications.
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    URL: http://dx.doi.org/10.1023/A:1020265417394
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    Endothelium-Derived Relaxing Factor: Discovery, Early Studies, and Identification as Nitric Oxide (1999)
    Springer
    Bioscience reports 19 (1999), S. 235-251 
    Details
    ISSN: 1573-4935
    Keywords: Endothelium derived relaxing factor (EDRF) ; nitric oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract The discovery, early studies and identification of endothelium-derived relaxing factor (EDRF) as nitric oxide, are described.
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    URL: http://dx.doi.org/10.1023/A:1020537506008
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    A hypothesis for the local control of osteoclast function by Ca2+, nitric oxide and free radicals (1992)
    Springer
    Bioscience reports 12 (1992), S. 369-380 
    Details
    ISSN: 1573-4935
    Keywords: osteoclast ; Ca2+ receptor ; peroxide ; nitric oxide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Several important conclusions have recently emerged fromin vitro studies on the resorptive cell of bone, the osteoclast. First, it has been established that osteoclast function is modulated locally, by changes in the local concentration of Ca2+ caused by hydroxyapatite dissolution. It is thought that activation by Ca2+ of a surface membrane Ca2+ receptor mediates these effects, hence providing a feedback control. Second, a number of molecules produced locally by the endothelial cell, with which the osteoclast is in intimate contact, have been found to affect bone resorption profoundly. For instance, the autocoid nitric oxide strongly inhibits bone resorption. Finally, reactive oxygen species have been found to aid bone resorption and enhance osteoclastic activity directly. Here, we will attempt to integrate these control mechanisms into a unified hypothesis for the local control of bone resorption.
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    URL: http://dx.doi.org/10.1007/BF01121500
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    The globalization of N deposition: ecosystem consequences in tropical environments (1999)
    Springer
    Biogeochemistry 46 (1999), S. 67-83 
    Details
    ISSN: 1573-515X
    Keywords: acidification ; anthropogenic nitrogen ; cations ; nitrate leaching ; nitric oxide ; nitrous oxide ; nutrient limitation ; phosphorus ; productivity ; tropical ecosystems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Human activities have more than doubled the inputs of nitrogen (N) into terrestrial systems globally. The sources and distribution of anthropogenic N, including N fertilization and N fixed during fossil fuel combustion, are rapidly shifting from the temperate zone to a more global distribution. The consequences of anthropogenic N deposition for ecosystem processes and N losses have been studied primarily in N-limited ecosystems in the temperate zone; there is reason to expect that tropical ecosystems, where plant growth is most often limited by some other resource, will respond differently to increasing deposition. In this paper, we assess the likely direct and indirect effects of increasing anthropogenic N inputs on tropical ecosytem processes. We conclude that anthropogenic inputs of N into tropical forests are unlikely to increase productivity and may even decrease it due to indirect effects on acidity and the availability of phosphorus and cations. We also suggest that the direct effects of anthropogenic N deposition on N cycling processes will lead to increased fluxes at the soilwater and soil-air interfaces, with little or no lag in response time. Finally, we discuss the uncertainties inherent in this analysis, and outline future research that is needed to address those uncertainties.
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    URL: http://dx.doi.org/10.1007/BF01007574
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    Contemporary and pre-industrial global reactive nitrogen budgets (1999)
    Springer
    Biogeochemistry 46 (1999), S. 7-43 
    Details
    ISSN: 1573-515X
    Keywords: ammonia emissions ; global nitrogen cycle ; nitric oxide ; nitrogen deposition ; nitrogen pollution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Increases and expansion of anthropogenic emissions of both oxidized nitrogen compounds, NOx, and a reduced nitrogen compound, NH3, have driven an increase in nitrogen deposition. We estimate global NOx and NH3 emissions and use a model of the global troposphere, MOGUNTIA, to examine the pre-industrial and contemporary quantities and spatial patterns of wet and dry NOy and NHx deposition. Pre-industrial wet plus dry NOx and NHx deposition was greatest for tropical ecosystems, related to soil emissions, biomass burning and lightning emissions. Contemporary NOy + NHx wet and dry deposition onto Northern Hemisphere (NH) temperate ecosystems averages more than four times that of pre-industrial N deposition and far exceeds contemporary tropical N deposition. All temperate and tropical biomes receive more N via deposition today than pre-industrially. Comparison of contemporary wet deposition model estimates to measurements of wet deposition reveal that modeled and measured wet deposition for both NO− 3 and NH+ 4 were quite similar over the U.S. Over Western Europe, the model tended to underestimate wet deposition of NO− 3 and NH+ 4 but bulk deposition measurements were comparable to modeled total deposition. For the U.S. and Western Europe, we also estimated N emission and deposition budgets. In the U.S., estimated emissions exceed interpolated total deposition by 3--6 Tg N, suggesting that substantial N is transported offshore and/or the remote and rural location of the sites may fail to capture the deposition of urban emissions. In Europe, by contrast, interpolated total N deposition balances estimated emissions within the uncertainty of each.
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    URL: http://dx.doi.org/10.1023/A:1006148011944
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    The Nitric Oxide Donor SIN-1 Is Free of Tolerance and Maintains Its Cyclic GMP Stimulatory Potency in Nitrate-Tolerant LLC-PK1 Cells (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 633-636 
    Details
    ISSN: 1573-904X
    Keywords: nitrate tolerance ; nitric oxide ; cyclic GMP ; SIN-1 ; molsidomine ; glyceryl trinitrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. Using an established cell culture model, the present study investigates whether linsidomine (SIN-1), a spontaneous donor of nitric oxide and active metabolite of the antianginal drug molsidomine, induces tolerance to its own cyclic GMP stimulatory action or shows a diminished response after tolerance induction with glyceryl trinitrate. Methods. Incubations with nitric oxide donors were carried out in LLC-PK1, kidney epithelial cells. Intracellular levels of cyclic GMP, the vasodilatory second messenger of nitric oxide, were determined by radioimmunoassay. Results. A 5-h preincubation with glyceryl trinitrate (0.01−100 μM) led to complete inhibition of a subsequent cyclic GMP stimulation by glyceryl trinitrate but left the cyclic GMP response to SIN-1 unaltered. Similarly, cyclic GMP elevations by the spontaneous nitric oxide donors sodium nitroprusside and spermine NONOate were not affected after pretreatment with glyceryl trinitrate. Moreover, pretreatment with SIN-1 (1−1000 μM) had no significant effect on SIN-1-dependent cyclic GMP stimulation. Conclusions. Our results show that in LLC-PK1, cells, SIN-1 is free of tolerance induction and not cross-tolerant to glyceryl trinitrate. This may be due to the spontaneous nitric oxide release from SIN-1, which in contrast to nitric acid esters does not require enzymatic bioactivation and may therefore be unaffected by nitrate tolerance.
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    URL: http://dx.doi.org/10.1023/A:1018804003745
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    NO Donor and Biological Properties of Different Benzofuroxans1 (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 956-960 
    Details
    ISSN: 1573-904X
    Keywords: nitric oxide ; NO ; benzofuroxans ; NO donors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To investigate the effect of benzofusion on NO donor properties and related biological activities of the furoxan system. The biological properties considered were the ability to increase the cytosolic levels of cGMP in C6 cells and vasodilation. Methods. NO donor properties were investigated either in the presence or the absence of cysteine by using the Griess reaction, chemiluminescence, and gas chromatography. Increase of cytosolic cGMP levels were evaluated by radioimmunoassay. Vasodilating activity was assessed on rat aorta strips precontracted with noradrenaline, in the presence and the absence of oxyhemoglobin (HbO2) and methylene blue (MB), respectively. Results. Benzofuroxan and its methyl and cyano derivatives were unable to release NO under the experimental conditions. Generally these compounds displayed feeble vasodilating properties and were able to weakly stimulate soluble guanylate cyclase (sGC). By contrast, benzodifuroxan and benzotrifuroxan were able to produce both NO• and its reduced form NO−, the nitroxyl anion. They displayed potent vasodilating properties and were able to increase cytosolic levels of cGMP in a concentration-dependent manner. Conclusions. The simple benzofuroxans considered here are devoid of the capability to release NO, they weakly stimulate sGC as well as manifest feeble vasodilating properties by a mechanism that does not involve a thiol-induced NO production. By contrast, benzodifuroxan and benzotrifuroxan behave as typical NO donor furoxans.
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    URL: http://dx.doi.org/10.1023/A:1018974409622
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    Contemporary and pre-industrial global reactive nitrogen budgets (1999)
    Springer
    Biogeochemistry 46 (1999), S. 7-43 
    Details
    ISSN: 1573-515X
    Keywords: ammonia emissions ; global nitrogen cycle ; nitric oxide ; nitrogen deposition ; nitrogen pollution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Increases and expansion of anthropogenic emissions of both oxidized nitrogen compounds, NOx, and a reduced nitrogen compound, NH3, have driven an increase in nitrogen deposition. We estimate global NOx and NH3 emissions and use a model of the global troposphere, MOGUNTIA, to examine the pre-industrial and contemporary quantities and spatial patterns of wet and dry NOy and NHx deposition. Pre-industrial wet plus dry NOx and NHx deposition was greatest for tropical ecosystems, related to soil emissions, biomass burning and lightning emissions. Contemporary NOy+NHx wet and dry deposition onto Northern Hemisphere (NH) temperate ecosystems averages more than four times that of preindustrial N deposition and far exceeds contemporary tropical N deposition. All temperate and tropical biomes receive more N via deposition today than pre-industrially. Comparison of contemporary wet deposition model estimates to measurements of wet deposition reveal that modeled and measured wet deposition for both NO 3 − and NH 4 + were quite similar over the U.S. Over Western Europe, the model tended to underestimate wet deposition of NO 3 − and NH 4 + but bulk deposition measurements were comparable to modeled total deposition. For the U.S. and Western Europe, we also estimated N emission and deposition budgets. In the U.S., estimated emissions exceed interpolated total deposition by 3-6 Tg N, suggesting that substantial N is transported offshore and/or the remote and rural location of the sites may fail to capture the deposition of urban emissions. In Europe, by contrast, interpolated total N deposition balances estimated emissions within the uncertainty of each.
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    URL: http://dx.doi.org/10.1007/BF01007572
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    The globalization of N deposition: ecosystem consequences in tropical environments (1999)
    Springer
    Biogeochemistry 46 (1999), S. 67-83 
    Details
    ISSN: 1573-515X
    Keywords: acidification ; anthropogenic nitrogen ; cations ; nitrate leaching ; nitric oxide ; nitrous oxide ; nutrient limitation ; phosphorus ; productivity ; tropical ecosystems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Human activities have more than doubled the inputs of nitrogen (N) into terrestrial systems globally. The sources and distribution of anthropogenic N, including N fertilization and N fixed during fossil fuel combustion, are rapidly shifting from the temperate zone to a more global distribution. The consequences of anthropogenic N deposition for ecosystem processes and N losses have been studied primarily in N-limited ecosystems in the temperate zone; there is reason to expect that tropical ecosystems, where plant growth is most often limited by some other resource, will respond differently to increasing deposition. In this paper, we assess the likely direct and indirect effects of increasing anthropogenic N inputs on tropical ecosytem processes. We conclude that anthropogenic inputs of N into tropical forests are unlikely to increase productivity and may even decrease it due to indirect effects on acidity and the availability of phosphorus and cations. We also suggest that the direct effects of anthropogenic N deposition on N cycling processes will lead to increased fluxes at the soil-water and soil-air interfaces, with little or no lag in response time. Finally, we discuss the uncertainties inherent in this analysis, and outline future research that is needed to address those uncertainties.
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    URL: http://dx.doi.org/10.1023/A:1006152112852
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    Spontaneous film formation from a polymer solution (1992)
    Springer
    Colloid & polymer science 270 (1992), S. 207-211 
    Details
    ISSN: 1435-1536
    Keywords: Spontaneousfilm formation ; filmformationmechanism ; thinfilms ; solublepolymers ; substitutedpoly (p-phenylene terephthalate) ; poly (carbonate) ; surfacetension ; FT-IR ; DTA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An unusual continuous film formation process of lateral pentyloxy substituted poly(p-phenylene terephthalate)s (s-PPPT) and poly(carbonate) (PC) is observed. A liquid film of polymer solution creeps over the surface of water dropped into the polymer solution. By vaporization of the solvent a solid polymer film is formed on the water surface and can be removed. The driving force for the film formation mechanism is assumed by the reduction of the surface tension of water. Experiments verify this mechanism by increasing the film formation speed using a gas stream, by reducing the formation speed through lowering the surface tension by rinsing agents, and by lowering the solubility of the polymer. As expected, no effects are found by variation of the pH-value of water. Necessary conditions for the film formation process are: good solubility of the polar polymers in organic solvents having a high vapor pressure, complete phase separation, solution density higher than water density, and a surrounding gas phase unsaturated with solvent vapor. The thickness of the mechanically stable films is less than 0.5 μm. The films are amorphous by microscopical, FT-IR, x-ray, and DTA investigations.
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    URL: http://dx.doi.org/10.1007/BF00655471
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    Solid State Phase Formation in the Bi2O3-PbO-CaO System (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 125-130 
    Details
    ISSN: 1572-8943
    Keywords: Bi2O3-PbO-CaO system ; DTA ; solid-state reactions ; X-ray diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Following our previous research, this work is dedicated to the study of phase formation in the subsolidus domain of the Bi2O3-PbO-CaO system. Former investigations performed by DTA/TGA and XRD have pointed out that under non-isothermal conditions only the formation of binary compounds occurs. Under such conditions these compounds could be non-equilibrium phases. In order to establish the conditions of formation of equilibrium phases, a study of the Bi2O3-PbO-CaO system, in isothermal conditions, was carried out. The results obtained in isothermal conditions have confirmed the presence of Bi2O3-rich solid solutions and Ca2PbO4 as main equilibrium phases. An attempt to represent the phase relations of the mentioned system at 700°C should be equally mentioned.
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    URL: http://dx.doi.org/10.1023/A:1010199728644
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    Synthesis and Thermal Study of 8-Hydroxyquinoline Derivatives of the Alkaline Earth Metals I. Strontium Complexes (1999)
    Springer
    Journal of thermal analysis and calorimetry 56 (1999), S. 519-524 
    Details
    ISSN: 1572-8943
    Keywords: DTA ; 8-hydroxyquinoline and its halogenated derivatives ; strontium ; TG ; thermal behaviour
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Strontium complexes of 5,7-dibromo-, 5,7-dichloro-, 7-iodo- and 5-chloro-7-iodo-8-hydroxyquinoline were precipitated from an aqueous ammonia and acetone medium. The complexes obtained were Sr[(C9H4ONBr2)2]·2.5H2O; Sr[(C9H4ONCl2)(OH)]·1.5H2O; Sr[(C9H5ONI)2]·5H2O and Sr[(C9H4ONICl)(OH)]·1.25H2O. The residues of their thermal decomposition were SrBr2; a mixture of SrCl2, SrCO3 and SrO; SrCO3 and SrCO3, respectively. All were characterized by means of thermogravimetry, differential thermal analysis, complexometry with EDTA, atomic absorption spectroscopy, IR spectroscopy and X-ray diffraction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010100610627
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