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  • Analytical Chemistry and Spectroscopy  (25.033)
  • Biochemistry and Biotechnology  (13.095)
  • Computational Chemistry and Molecular Modeling  (8.042)
  • stability
  • Wiley-Blackwell  (46.224)
  • Springer  (680)
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  • 201
    Digitale Medien
    Digitale Medien
    Isolation, Characterization, and Stability of Positional Isomers of Mono-PEGylated Salmon Calcitonins (1999)
    Springer
    Pharmaceutical research 16 (1999), S. 813-818 
    Details
    ISSN: 1573-904X
    Schlagwort(e): calcitonin ; polyethylene glycol ; PEGylation ; peptide ; tryptic digestion ; stability ; HPLC
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Purpose. To separate and characterize the different positional isomers of mono-PEGylated salmon calcitonins (mono-PEG-sCTs) and to evaluate the effects of the PEGylation site on the stability of different mono-PEG-sCTs in rat kidney homogenate. Methods. Mono-PEG-sCTs were prepared using succinimidyl carbonate monomethoxy polyethylene glycol (5,000 Da) and separated by gel-filtration HPLC followed by reversed-phase HPLC. To characterize PEGylated sCTs, matrix-assisted laser desorption ionization time of flight mass spectrometry (M ALDI-TOF MS) and reversed-phase HPLC of the trypsin digested samples were performed. Mono-PEG-sCTs and sCT in rat kidney homogenates were measured by column-switching reversed-phase HPLC with on-line detection of the radioiodinated samples using a flow-through radioisotope detector. Results. Three different mono-PEGylated sCTs were separated by reversed-phase gradient HPLC. From the MALDI-TOF MS analysis, the average molecular weight of mono-PEG-sCTs was confirmed as around 8650 Da. The presence of PEG moiety in the mono-PEG-sCTs was also manifested by the fact that the distance between two adjacent mass spectum lines was 44 Da which corresponds to PEG monomer unit. Tryptic digestion analysis demonstrated that these mono-PEG-sCTs are 3 positional isomers of N-terminus, Lys18- and Lys11-residue modified mono-PEGylated sCTs. The degradation half-life of these 3 positional isomers in rat kidney homogenates significantly increased in order of the N-terminus (125.5 min), Lys11- (157.3 min), and Lysl8-residue modified mono-PEGylated sCT (281.5 min) over the native sCT (4.8 min). Conclusions. Three positional isomers of mono-PEGylated sCTs were purified and characterized. Of these, the resistance to proteolytic degradation was highest for the Lysl8-residue modified mono-PEG-sCT. These studies demonstrate that the in vivo stability of PEGylated sCTs is highly dependent on the site of PEG molecule attachment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1018861616465
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  • 202
    Digitale Medien
    Digitale Medien
    On the Stability of a Laminar Wall Jet with Heat Transfer (1999)
    Springer
    Flow, turbulence and combustion 62 (1999), S. 137-162 
    Details
    ISSN: 1573-1987
    Schlagwort(e): laminar wall jet ; heat transfer ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The hydrodynamic stability of a low speed, plane, non-isothermal laminar wall jet at a constant temperature boundary condition was investigated theoretically and experimentally. The mean velocity and temperature profiles used in the stability analysis were obtained by implementing the Illingworth–Stewartson transformation that allows one to extend the classical Glauert solution to a thermally non-uniform flow. The stability calculations showed that the two unstable eigenmodes coexisting at moderate Reynolds numbers are significantly affected by the heat transfer. Heating is destabilizing the flow while cooling is stabilizing it. However, the large-scale instabilities associated with the inflection point of the velocity profile still amplify in spite of the high level of the stabilizing temperature difference. The calculated stability characteristics of the wall jet with heat transfer were compared with experimental data. The comparison showed excellent agreement for small amplitudes of the imposed perturbations. The agreement is less good for the phase velocities of the sub-harmonic wave and this is attributed to experimental difficulties and to nonlinear effects.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009965531203
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  • 203
    Digitale Medien
    Digitale Medien
    Orbital Migration Of Giant Planets: Using Numerical Integration To Investigate Consequences For Other Bodies (1999)
    Springer
    Earth, moon and planets 87 (1999), S. 103-115 
    Details
    ISSN: 1573-0794
    Schlagwort(e): Accretion ; exoplanetary system ; extrasolar planets ; numerical integration ; orbital migration ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie , Physik
    Notizen: Abstract A number of extrasolar planets have been detected in close orbits around nearby stars. It is probable that these planets did not form in these orbits but migrated from their formation locations beyond the ice line. Orbital migration mechanisms involving angular momentum transfer through tidal interactions between the planets and circumstellar gas-dust disks or by gravitational interaction with a residual planetesimal disk together with several means of halting inward migration have been identified. These offer plausible schemes to explain the orbits of observed extrasolar giant planets and giant planets within the Solar System. Recent advances in numerical integration methods and in the power of computer workstations have allowed these techniques to be applied to modelling directly the mechanisms and consequences of orbital migration in the Solar System. There is now potential for these techniques also to be applied to modelling the consequences of the orbital migration of planets in the observed exoplanetary systems. In particular the detailed investigation of the stability of terrestrial planets in the habitable zone of these systems and the formation of terrestrial planets after the dissipation of the gas disk is now possible. The stability of terrestrial planets in the habitable zone of selected exoplanetary systems has been established and the possibility of the accretion of terrestrial planets in these systems is being investigated by the author in collaboration with Barrie W. Jones (Open University), and with John Chambers (NASA-Ames) and Mark Bailey of Armagh Observatory, using numerical integration. The direct simulation of orbital migration by planetesimal scattering must probably await faster hardware and/or more efficient algorithms.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1017996927696
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  • 204
    Digitale Medien
    Digitale Medien
    Robust Stability of Multivariate Polynomials. Part 1: Small Coefficient Perturbations (1999)
    Springer
    Multidimensional systems and signal processing 10 (1999), S. 7-20 
    Details
    ISSN: 1573-0824
    Schlagwort(e): multivariate polynomials ; stability ; robust stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract This paper presents a detailed analysis of some classes of stable multivariate polynomials. The main aim of the analysis is to give conditions under which polynomials preserve stability when they are subjected to small coefficient variations. The maximal class of such polynomials is introduced. Some basic properties of polynomials from this class are obtained.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008456918178
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  • 205
    Digitale Medien
    Digitale Medien
    Stability and resilience in benthic macroinvertebrate assemblages (1999)
    Springer
    Hydrobiologia 403 (1999), S. 123-133 
    Details
    ISSN: 1573-5117
    Schlagwort(e): disturbance ; stability ; resilience ; Trichoptera ; Ephemeroptera ; Psychomyia
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Benthic macroinvertebrate assemblages of Bushkill Creek, Northampton County, PA were studied at the same site during the 1970s (11 dates) and 1990s (8 dates) to evaluate stability and resilience. In the 1970s, a Surber sampler was used, and in the 1990s, a Hess sampler. Assemblages appeared stable over a wide range of environmental stresses with the exception of 1994–1995 when total numbers and total Trichoptera decreased. Taxa richness and EPT indices varied little in 1994–1995 from other sampled years. By July 1996, all metrics (Trichoptera numbers, total numbers, taxa richness, EPT index, Bray-Curtis Index) resembled the 1970s exception for lower wet weight. Bray-Curtis indices and taxa composition were similar in July 1972 and July 1996, suggesting assemblage stability over 25 years. The Trichoptera, Psychomyia (Psychomiidae) and Leucotrichia (Hydroptilidae), decreased during the 1990s and never rebounded to 1970s numbers. During winter 1994, the coldest temperatures and greatest cumulative snowfall occurred in the region. These conditions probably stressed the assemblage with low temperatures, anchor/frazil ice and ice break-up. The assemblage was then exposed to four bankful floods in winter/spring 1994 and five bankful floods in winter/spring 1996. Recovery time following these multiple disturbances was 27 months. Previous recovery times from winter and flood disturbances were considerably shorter (2–5 months). The 1990s recovery time (5–9 times previusly recorded) for this assemblage was apparently extended by multiple physical disturbances, outside the predicted range. The assemblages had not been previously exposed to such severe conditions and, therefore, recovery time was extended. Despite severe weather conditions, the assemblage recovered and exhibited both stability and resilience in its return to an assemblage similar to the 1970s.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1003711928980
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  • 206
    Digitale Medien
    Digitale Medien
    Procedures for the characterisation of bioaerosol particles. Part I: aerosolisation and recovery agent effects (1999)
    Springer
    Aerobiologia 15 (1999), S. 267-280 
    Details
    ISSN: 1573-3025
    Schlagwort(e): aerosolisation effects ; bioaerosol ; bioaerosol sampling ; effects of recovery agents ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The sampling and assay of bioaerosols are important ina number of industrial and health-care applications. Airborne microorganisms are notoriously difficult toenumerate accurately under such conditions and nosingle procedure is suitable for all applications. Problems are compounded by the differences in assaymethod or sampler type selected, making theinterpretation of results difficult.Understanding the airborne behaviour of microorganismsover a range of environmental conditions is vital ifprocedures are to be defined and recommended for theassessment of bioaerosols. Microorganisms that arerobust over a wide range of conditions are ideal astracer particles. Unfortunately, the large majorityof non-fungal bioaerosols are susceptible to damage. A predictable assessment procedure is required whichwill not affect the viability of the collectedsample. This paper examines how aerosolisation may affect the characteristics of two speciesof microorganism (Pseudomonas fluorescens andMS2 coliphage). It forms part of a larger programmeto develop standards for the assessment of biologicalparticles. The aim of the work was to develop procedures toexamine the effects of aerosolisation onmicroorganisms, with particular reference topre-aerosolisation protocol (spray suspension age) andpost-sampling handling protocol (aerosol age incollection solution). These procedures were then usedto examine the effect of recovery agents, addedto the spray suspension prior to aerosolisation, onthe culturability of E.coli. Aerosolisation reduces the culturability of P. fluorescensand the viability of viability of MS2coliphage. Pre-sampling and post-collection handlingand storage of these aerosolised microorganisms werealso found to have an effect. This and earlierstudies have shown that the culturable fraction ofmicroorganisms can be affected by the same factorsdescribed above. Of five microorganisms tested so farin the main programme, only Penicillium expansumspores were shown to be robust and stable with aconstant culturable fraction. Therefore, recommendinga particular microorganism (apart from P. expansum) as an airborne biological standard foraerosol studies is not advised. It is recommendedthat a microorganism, representative of the envisagedapplication, be characterised it in terms of theaerosolisation parameters, storage time and conditionsin the manner reported in this study. This can beachieved using the experimental equipment described.The addition of 0.1 mM concentrations of the sugarsinositol, trehalose and raffinose to spray suspensionsof Escherichia coli, prior to aerosolisation,made no significant difference to the culturablefraction of the aerosol.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007638711384
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  • 207
    Digitale Medien
    Digitale Medien
    Equilibrium stability of generalized Birkhoff's autonomous system (1999)
    Springer
    Applied mathematics and mechanics 20 (1999), S. 564-567 
    Details
    ISSN: 1573-2754
    Schlagwort(e): generalized Birkhoff's system ; equilibrium state ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Mathematik , Physik
    Notizen: Abstract In this paper, equilibrium stability of generalized Birkhoff's autonomous system is discussed. First, equilibrium equations of generalized Birkhoff's autonomous system are set up, and then the linear approximate method and direct method of stability in equilibrium state are studied. Some results on equilibrium of generalized Birkhoff's autonomous system are obtained on the basis of Lyapunov's thorem. Last, the application of the results is illustrated with an example.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02463754
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  • 208
    Digitale Medien
    Digitale Medien
    Portfolio optimization via stochastic programming: Methods of output analysis (1999)
    Springer
    Mathematical methods of operations research 50 (1999), S. 245-270 
    Details
    ISSN: 1432-5217
    Schlagwort(e): Key words: Portfolio optimization ; stochastic programming ; stability ; postoptimality ; worst-case analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik , Wirtschaftswissenschaften
    Notizen: Abstract. Solutions of portfolio optimization problems are often influenced by errors or misspecifications due to approximation, estimation and incomplete information. Selected methods for analysis of results obtained by solving stochastic programs are presented and their scope illustrated on generic examples – the Markowitz model, a multiperiod bond portfolio management problem and a general strategic investment problem. The approaches are based on asymptotic and robust statistics, on the moment problem and on results of parametric optimization.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s001860050097
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  • 209
    Digitale Medien
    Digitale Medien
    The effect of Li and La on NiO/Al2O3 catalyst for CH4/O2 to syngas reaction (1999)
    Springer
    Reaction kinetics and catalysis letters 68 (1999), S. 243-247 
    Details
    ISSN: 1588-2837
    Schlagwort(e): Methane partial oxidation ; nickel-based catalysts ; stability ; sintering and loss of nickel
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The thermal stability and an 80 h life test over nickel-based catalysts for CH4/O2 to syngas reaction were investigated by flow-reactor, XPS, XRD and AAS analysis. The results indicate that the introduction of Li and La not only stabilized the support γ-Al2O3 phase, but also suppressed the sintering and loss of nickel, and in addition, enhanced the ability to suppress the carbon-deposition over NiO/Al2O3 during the high-temperature reaction.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02475508
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  • 210
    Digitale Medien
    Digitale Medien
    A Multiple-Shooting Technique for Optimal Control (1999)
    Springer
    Journal of optimization theory and applications 102 (1999), S. 299-313 
    Details
    ISSN: 1573-2878
    Schlagwort(e): Comparison of methods ; optimal control ; sensitivity ; shooting methods ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract A new method for solving optimal control problems, here called multiple NOC shooting, is presented. It is developed from NOC shooting. It has some advantages over its parent and over multiple shooting, which are both successful, high-accuracy methods for optimal control. A comparison of the three methods is given, incorporating two examples.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1021728407151
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  • 211
    Digitale Medien
    Digitale Medien
    New Linear Program Performance Bounds for Queueing Networks (1999)
    Springer
    Journal of optimization theory and applications 100 (1999), S. 575-597 
    Details
    ISSN: 1573-2878
    Schlagwort(e): Queueing networks ; scheduling ; stability ; performance evaluation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract We obtain new linear programs for bounding the performance and proving the stability of queueing networks. They exploit the key facts that the transition probabilities of queueing networks are shift invariant on the relative interiors of faces and the cost functions of interest are linear in the state. A systematic procedure for choosing different quadratic functions on the relative interiors of faces to serve as surrogates of the differential costs in an inequality relaxation of the average cost function leads to linear program bounds. These bounds are probably better than earlier known bounds. It is also shown how to incorporate additional features, such as the presence of virtual multi-server stations to further improve the bounds. The approach also extends to provide functional bounds valid for all arrival rates.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022638523391
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  • 212
    Digitale Medien
    Digitale Medien
    Binding and Ionophoric Properties of Polythioamide Compounds. Ag(I) and Hg(II) Selectivities (1999)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 34 (1999), S. 277-289 
    Details
    ISSN: 1573-1111
    Schlagwort(e): complexes ; stability ; extraction ; transport ; tetrathiolactams
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The synthesis of tetrathiolactams and related di- and tetrathioamide compounds is described. The formation constants of their heavy-metal complexes are determined by using the strong UV absorption of the thioamide chromophore. Extraction and transport abilities of tetrathioamide ionophores show selectivities for Ag(I) and Hg(II) cations over alkali, alkaline-earth or other heavy metal cations including transition metals such as Co(II).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008093510236
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  • 213
    Digitale Medien
    Digitale Medien
    Polarographic Studies on Anion Coordination Chemistry. Host–Guest Interactions of Hexacyclen and Pentacyclen with Pyrophosphate, Selenite, Selenate, Molybdate and Tungstate Anions (1999)
    Springer
    Journal of inclusion phenomena and macrocyclic chemistry 34 (1999), S. 455-464 
    Details
    ISSN: 1573-1111
    Schlagwort(e): hexacyclen ; pentacyclen ; anion complexes ; stoichiometry ; stability ; polarography
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The complexation of protonated hexacyclen and pentacyclen with pyrophosphate, selenite, selenate, molybdate and tungstate anions was studied by differential pulse polarography at 25 °C. The stoichiometry and stability of the resulting anion complexes were evaluated from the pH and concentration-dependence of the peak potentials, respectively. The results established 1 : 1 anion receptor complexation in all cases. In the case of all anions studied, hexacyclen was found to form more stable anion complexes than pentacyclen. The fact that the anion-receptor complexation depends on the structural features of both the anions and the macrocycles used is indicative of a steric controlled interaction.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008050909119
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  • 214
    Digitale Medien
    Digitale Medien
    Closed-Loop Stability Monitoring of Axial Flow Compression Systems (1999)
    Springer
    Nonlinear dynamics 20 (1999), S. 181-196 
    Details
    ISSN: 1573-269X
    Schlagwort(e): monitoring ; stability ; compressors ; axial flow compressors ; stall ; surge ; bifurcation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract Monitoring systems are proposed for the detection of incipient instability in axial flow compression systems. The work employs generic features associated with the response to noise inputs of systems bordering on instability. Based on these generic features, a closed-loop monitoring system is proposed. Numerical simulation is used to illustrate the operation of the proposed closed-loop monitoring system.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004596213600
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  • 215
    Digitale Medien
    Digitale Medien
    On the Reconstitution Problem in the Multiple Time-Scale Method (1999)
    Springer
    Nonlinear dynamics 19 (1999), S. 135-158 
    Details
    ISSN: 1573-269X
    Schlagwort(e): perturbation methods ; higher-order approximations ; dynamical systems ; codimension ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract Higher-order multiple-scale methods for general multiparameter mechanical systems are studied. The role played by the control and imperfection parameters in deriving the perturbative equations is highlighted. The definition of the codimension of the problem, borrowed from the bifurcation theory, is extended to general systems, excited either externally or parametrically. The concept of a reduced dynamical system is then invoked. Different approaches followed in the literature to deal with reconstituted amplitude equations are discussed, both in the search for steady-state solutions and in the analysis of stability. Four classes of methods are considered, based on the consistency or inconsistency of the approach, and on the completeness or incompleteness of the terms retained in the analysis. The four methods are critically compared and general conclusions drawn. Finally, three examples are illustrated to corroborate the findings and to show the quantitative differences between the various approaches.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008330423238
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  • 216
    Digitale Medien
    Digitale Medien
    Articulated Pipes Conveying Fluid Pulsating with High Frequency (1999)
    Springer
    Nonlinear dynamics 19 (1999), S. 173-193 
    Details
    ISSN: 1573-269X
    Schlagwort(e): fluid conveying pipes ; high-frequency pulsating fluid ; separation of slow and fast motion ; stability ; nonlinear dynamics
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract Stability and nonlinear dynamics of two articulated pipes conveying fluid with a high-frequency pulsating component is investigated. The non-autonomous model equations are converted into autonomous equations by approximating the fast excitation terms with slowly varying terms. The downward hanging pipe position will lose stability if the mean flow speed exceeds a certain critical value. Adding a pulsating component to the fluid flow is shown to stabilize the hanging position for high values of the ratio between fluid and pipe-mass, and to marginally destabilize this position for low ratios. An approximate nonlinear solution for small-amplitude flutter oscillations is obtained using a fifth-order multiple scales perturbation method, and large-amplitude oscillations are examined by numerical integration of the autonomous model equations, using a path-following algorithm. The pulsating fluid component is shown to affect the nonlinear behavior of the system, e.g. bifurcation types can change from supercritical to subcritical, creating several coexisting stable solutions and also anti-symmetrical flutter may appear.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008326812760
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  • 217
    Digitale Medien
    Digitale Medien
    Double Hopf Bifurcations and Chaos of a Nonlinear Vibration System (1999)
    Springer
    Nonlinear dynamics 19 (1999), S. 313-332 
    Details
    ISSN: 1573-269X
    Schlagwort(e): double pendulum system ; double Hopf bifurcation ; stability ; chaos
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract A double pendulum system is studied for analyzing the dynamic behaviour near a critical point characterized by nonsemisimple 1:1 resonance. Based on normal form theory, it is shown that two phase-locked periodic solutions may bifurcate from an initial equilibrium, one of them is unstable and the other may be stable for certain values of parameters. A secondary bifurcation from the stable periodic solution yields a family of quasi-periodic solutions lying on a two-dimensional torus. Further cascading bifurcations from the quasi-periodic motions lead to two chaoses via a period-doubling route. It is shown that all the solutions and chaotic motions are obtained under positive damping.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008347523779
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  • 218
    Digitale Medien
    Digitale Medien
    Preventing buoyancy-driven flows of two Bingham fluids in a closed pipe – Fluid rheology design for oilfield plug cementing (1999)
    Springer
    Journal of engineering mathematics 36 (1999), S. 327-348 
    Details
    ISSN: 1573-2703
    Schlagwort(e): Bingham fluids ; multi-layer flow ; no-flow/yield criteria ; stability ; variational methods.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Abstract The mechanically unstable situation of a heavy Bingham fluid resting on top of a light Bingham fluid in an inclined closed-ended pipe can be stabilised if the fluids have sufficiently large yield stresses. This paper focuses on determining the yield stresses that are sufficient to keep the fluids statically stable for a given fluid density difference, pipe diameter and pipe inclination. The results are applicable to a broad class of practically observable flows. This situation provides an idealised model for the oilfield process of plug cementing.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004511113745
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  • 219
    Digitale Medien
    Digitale Medien
    A Multibody Motion Stability Analysis (1999)
    Springer
    Multibody system dynamics 3 (1999), S. 287-299 
    Details
    ISSN: 1573-272X
    Schlagwort(e): multibody dynamics ; symbol manipulation ; linearization ; stability ; Floquet theory
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract It is shown that use of AUTOLEV, a symbol manipulation computer program for mechanics analyses, can greatly facilitate the stability analysis of motions of multibody systems.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009882505218
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  • 220
    Digitale Medien
    Digitale Medien
    The onset of steady Bénard-Marangoni convection in a two-layer system of conducting fluid in the presence of a uniform magnetic field (1999)
    Springer
    Journal of engineering mathematics 35 (1999), S. 385-404 
    Details
    ISSN: 1573-2703
    Schlagwort(e): Bénard-Marangini convection ; conducting fluids ; stability ; two-layer system.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik , Technik allgemein
    Notizen: Abstract The onset of steady Bénard-Marangoni convection in two horizontal liquid layers of electrically conducting immiscible fluids subjected to a uniform vertical magnetic field and temperature gradient is analysed by means of a combination of analytical and numerical techniques. The free surface can be either deformable or nondeformable and the interface between the fluids is always assumed to be flat. The effect of the lower layer on the critical values of Rayleigh, Marangoni and wave numbers for the onset of steady convection is investigated. When the free surface is nondeformable, the critical parameters for the onset of pure Marangoni convection are increased, whereas for the onset of pure Bénard convection they are decreased compared to the single-layer model. The results for a single-layer and for two-layers are qualitatively similar for Bénard-Marangoni convection when the free surface is deformable. All disturbances can be stabilized with sufficiently strong magnetic field when the free surface is nondeformable. If the free surface is allowed to deform and gravity waves are excluded, then the layers are always unstable to disturbances with sufficiently small wave number with magnetic field. Inclusion of gravity waves has a stabilizing effect on certain disturbances of small wave number in the presence of weak or moderate magnetic field.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004439231890
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  • 221
    Digitale Medien
    Digitale Medien
    Dynamics of Oscillators with Strongly Nonlinear Asymmetric Damping (1999)
    Springer
    Nonlinear dynamics 20 (1999), S. 221-246 
    Details
    ISSN: 1573-269X
    Schlagwort(e): Coulomb friction ; asymmetric damping ; exact periodic motions ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract Dynamics of a class of strongly nonlinear single degree of freedom oscillators is investigated. Their common characteristic is that they possess piecewise linear damping properties, which can be expressed in a general asymmetric form. More specifically, the damping coefficient and a constant parameter appearing in the equation of motion are functions of the velocity direction. This class of oscillators is quite general and includes other important categories of mechanical systems as special cases, like systems with Coulomb friction. First, an analysis is presented for locating directly exact periodic responses of these oscillators to harmonic excitation. Due to the presence of dry friction, these responses may involve intervals where the oscillator is stuck temporarily. Then, an appropriate stability analysis is also presented together with some quite general bifurcation results. In the second part of the work, this analysis is applied to several example systems with piecewise linear damping, in order to reveal the most important aspects of their dynamics. Initially, systems with symmetric characteristics are examined, for which the periodic response is found to be symmetric or asymmetric. Then, dynamical systems with asymmetric damping characteristics are also examined. In all cases, emphasis is placed on investigating the low forcing frequency ranges, where interesting dynamics is noticed. The analytical predictions are complemented with results obtained by proper integration of the equation of motion, which among other responses reveal the existence of quasiperiodic, chaotic and unbounded motions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008398813070
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  • 222
    Digitale Medien
    Digitale Medien
    Composition and Microstructure Determination of the Syndiotactic Copolymer of para-Methylstyrene and Styrene by Pyrolysis Gas Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 11-16 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Pyrolysis gas chromatography ; microstructure determination ; syndiotactic copolymers ; styrenes ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---The composition and microstructure of syndiotactic para-methylstyrene/styrene copolymer was determined by a pyrolysis gas chromatography (Py-GC) method. This method uses the styrene and para-methylstyrene monomer peak intensities to determine the styrene and para-methylstyrene composition in the copolymer. The number average sequence length of styrene was calculated by using the triad peak intensities. Because of the low concentration of para-methylstyrene in the copolymer, the number average sequence length of para-methylstyrene was determined with formulas that incorporate the copolymer composition and the number average sequence length of styrene. The distribution of para-methylstyrene defined by the terms “percent of single units” and “percent of desired distribution” was calculated by the number average sequence of para-methylstyrene. This method has been tested with copolymers containing up to 24 mole% of para-methylstyrene. The composition results from Py-GC of para-methylstyrene and styrene copolymers used in this study were in excellent agreement with 1H-NMR results.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 223
    Digitale Medien
    Digitale Medien
    Superior ECD Performance through Design and Application (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 24-28 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; ECD ; Micro-ECD ; GC detector ; organochlorine pesticides ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---A new ECD, the HP 6890 Series Micro-ECD, was designed to address inherent deficiencies in classical electron capture detectors (ECD), especially with respect to sensitivity, linearity, dynamic range, and ruggedness. Several novel technologies were incorporated in the totally new design and were refined through practical testing and user feedback. Validation of the micro-ECD performance was accomplished through side-by-side testing of the Micro-ECD with previous ECDs following US EPA Contract Laboratory Program methods for pesticides and PCBs. In addition, extensive interviews were conducted with early users of the Micro-ECD who also had experience with other designs running a variety of ECD methods. The design and resulting performance improvements are described.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 224
    Digitale Medien
    Digitale Medien
    Experimentation with Chiral CE: The Application of Two Chiral Selectors and Partial Filling with Chiral Selector (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 33-38 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Capillary electrophoresis ; chiral separation ; negatively charged chiral selectors ; capillary filling methods ; dual systems ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---Data on the use of two chiral selectors, namely 18-crown-6 tetracarboxylic acid and a negatively charged cyclodextrin derivative (sulfated-β-cyclodextrin or carboxymethyl-β-cyclodextrin), in the same background electrolyte are presented. The use of such dual systems has a considerable influence on the resolution, as illustrated for the separation of tryptophan derivatives. Reduction of the consumption of chiral selector without significant loss in resolution was obtained by only partly filling the capillary and applying a run buffer without selector. This is illustrated for the chiral separation of tryptophan hydroxamate and the diastereomeric and enantiomeric separation of the dipeptide α/b-AspPhe-OMe.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 225
    Digitale Medien
    Digitale Medien
    Determination of Free Diterpenes in Green and Roasted Coffees (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 43-46 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Green and roasted coffee ; diterpenes ; cafestol ; kahweol ; 16-O-methylcafestol ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---The three coffee diterpenes cafestol, kahweol, and 16-O-methylcafestol are mostly esterified with fatty acids. Little has been published about the diterpenes occurring in the free form. By means of gel permeation chromatography on Bio Beads S-X3, it is now possible to simultaneously analyze and quantify the small amounts of these compounds by RP-HPLC. In this way, free kahweol was first proved to be an ingredient of Robusta coffee. Various Arabica and Robusta coffees - both green and roasted - were investigated. Free diterpenes were found in green coffees in amounts below 200 mg/kg dry matter. In comparison to the respective total diterpene content determined by the same HPLC method after saponification of the coffee oil, the proportion of free diterpenes ranged from 0.7 to 3.5 %. During the roasting process, the three uncombined diterpenes behaved similarly: free 16-O-methylcafestol, cafestol as well as kahweol were degraded with increasing roasting temperature.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 226
    Digitale Medien
    Digitale Medien
    Optimization through Factorial Planning of the Use of Ethanol : Water as a Mobile Phase for Reversed Phase HPLC (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 52-54 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Ethanol ; mobile phase ; factorial planning ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 227
    Digitale Medien
    Digitale Medien
    Levels of Organotin Compounds in Burbot (Lota Lota) from Norwegian Lakes (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 177-180 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Fresh water systems ; burbot ; organotin compounds ; speciation analysis ; GC-AED ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---No abstract
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 228
    Digitale Medien
    Digitale Medien
    RP-HPLC and GC-MS Techniques for the Quantitative Analysis of Substituted 1,2,4-Trioxanes and their Thermolysis Products in Solution (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 67-69 
    Details
    ISSN: 0935-6304
    Schlagwort(e): RP-HPLC ; GC-MS ; trioxanes ; thermolysis products ; quantitative analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 229
    Digitale Medien
    Digitale Medien
    A Robust Thermal Modulator for Comprehensive Two-Dimensional Gas Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 3-10 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Multidimensional Gas Chromatography ; orthogonal separations ; GC×GC ; comprehensive two-dimensional chromatography ; characterization of gasoline ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---In comprehensive two-dimensional gas chromatography (GC×GC), two capillary columns are connected in series through an interface known as a “thermal modulator”. This device transforms effluent from the first capillary column into a series of sharp injection-like chemical pulses suitable for high-speed chromatography on the second column. Dramatic increases in the resolving power, sensitivity, and speed of the gas chromatograph result. This paper describes the development of a robust and reliable thermal modulator for GC×GC.
    Zusätzliches Material: 5 Ill.
    Materialart: Digitale Medien
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  • 230
    Digitale Medien
    Digitale Medien
    Effect of Mobile Phase Components on the Separation of Polypeptides Using Carbon Dioxide-Based Mobile Phases (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 74-78 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Polypeptides ; subcritical fluid chromatography ; supercritical fluid chromatography ; carbon dioxide ; additives ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---The effect of mobile phase modifier and additive on the chromatographic properties of various small polypeptides was explored under subcritical conditions. A polymeric column was used to separate various enkephalin analogs, bradykinin, and oxytocin using a carbon dioxide-based mobile phase with either an ethanol or a 2-methoxyethanol modifier. The role of the modifier was found to be secondary to that of the mobile phase additive. As progressively stronger acidic mobile phase additives were used, the peak profiles of the various polypeptides improved and retention decreased. Heptadecafluorooctanesulfonic acid was found to be the most useful additive for these types of solutes under near-critical conditions, while the potassium salt of heptadecafluorooctanesulfonic acid failed to elute any of the polypeptides. At low temperatures, pressure gradients with a carbon dioxide/ethanol/heptadecafluorooctanesulfonic acid ternary mobile phase produced reasonably good peak profiles with the polymeric column.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
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  • 231
    Digitale Medien
    Digitale Medien
    γ(δ)-Thionolactones - Enantioselective Capillary GC and Sensory Characteristics of Enantiomers (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 89-92 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Enantioselective gas chromatography ; heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin ; heptakis(2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin ; γ(δ)-thionolactones ; olfactometry ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---The even numbered γ(δ)-thionolactones (C6-C12) were investigated, using heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)- and heptakis(2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin as chiral stationary phases in capillary gas chromatography. The odor characteristics of γ(δ)-thionolactone enantiomers were investigated by enantioselective gas chromatography/olfactometry.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 232
    Digitale Medien
    Digitale Medien
    Programmable Temperature Vaporizer (PTV) Applied to the Triglyceride Analysis of Milk Fat (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 93-96 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Capillary GC ; PTV and on-column injectors ; milk fat triglycerides ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---The PTV (Programmable Temperature Vaporizer) is a split/splitless injector which allows the sample to be introduced at a relatively low temperature, thus affording accurate and reproducible sampling. After injection the PTV is rapidly heated to transfer the vaporized components into the capillary column. This type of injector has proved to be an efficient tool for the evaluation of fatty acids, essential oils, and pesticides in food analysis. In this work the suitability of PTV for the analysis of milk fat purity by the Official EU method was evaluated. This method is based on the gas chromatographic determination of triglycerides only according to their total number of carbon atoms followed by the application of formulae deriving from multiple linear regressions. The analysis is currently carried out with a packed column or a short capillary column and an on-column injection system. Several samples of pure milk fat and mixtures of milk fat with foreign fat were analyzed with the same capillary column and by using both PTV and on-column injection systems. The results show that the gas chromatographic profile obtained by PTV is comparable with that obtained by the on-column injector, while repeatability and reproducibility data meet the requirements indicated in the Official Method. Therefore, this study demonstrates that it is possible to use the PTV instead of the on-column injector to determine the purity of milk fat with this method.
    Zusätzliches Material: 1 Ill.
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  • 233
    Digitale Medien
    Digitale Medien
    Study of the Linear Range in HPLC Analyses with UV Detection: Methodology and Experimental Application to the Influence of the Analyte UV Spectrum (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 217-221 
    Details
    ISSN: 0935-6304
    Schlagwort(e): HPLC ; UV detection ; linear range ; method validation ; Beer-Lambert law ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Determination of the linear range is one of the main concerns in validation of an HPLC analysis method. It is particularly important since single point calibration will be then used routinely. We proposed an iterative methodology to handle this problem. The idea was, at each step, to test statistically whether the following point belonged to the same regression line. The methodology was then used to evaluate quantitatively the effect on linear range of a shift in detection wavelength or of the detector bandwidth. Although experimental results were globally in accordance with spectroscopic theory, magnitudes observed were rather large. So the linear range could vary by a factor of over 2 with changes in conditions that remained within the range of current practical values. Changes in detection wavelength were limited to about fifteen nm around λmax and the detector used was considered to be representative of modern high-performance UV detectors. The question of how to take consequences in method validation into account was raised. The solution proposed recommended that the validation was undertaken in conditions as close as possible to those where the method would be conducted routinely. This means with the same instrumentation and on the product of interest for analyses.
    Zusätzliches Material: 6 Ill.
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  • 234
    Digitale Medien
    Digitale Medien
    Equilibrium-Sorptive Enrichment: A Novel Technique for Trace Analysis in Air (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 231-234 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Trace analysis ; air samples ; BTX ; equilibrium-sorptive enrichment ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---No abstract
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 235
    Digitale Medien
    Digitale Medien
    Theoretical Design Considerations for Multi-capillary Columns in Fast Gas Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 119-122 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Fast gas chromatography ; multi-capillary column ; band broadening ; simulation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 236
    Digitale Medien
    Digitale Medien
    GC-MS Determination of Kava-Pyrones in Alpinia zerumbet Leaves (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 129-130 
    Details
    ISSN: 0935-6304
    Schlagwort(e): GC-MS ; kava pyrones ; Alpinia zerumbet ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 237
    Digitale Medien
    Digitale Medien
    On-Line Coupling of Separation Techniques to NMR (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 135-143 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Chromatographic separation techniques ; High Performance Liquid Chromatography (HPLC) ; Gel Permeation Chromatography (GPC) ; Supercritical Fluid Chromatography (SFC) ; Capillary HPLC ; Nuclear Magnetic Resonance (NMR) spectroscopy ; hyphenation of chromatography with NMR spectroscopy ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---The hyphenation of chromatographic separation techniques with NMR spectroscopy is one of the most powerful and time-saving methods for the separation and structural elucidation of unknown compounds and molecular compositions of mixtures. Most of the routinely used NMR flow-cells have detection volumes between 40-180 μL for conventional separations with analytical columns, and the newest designs employ detection volumes in the order of 200 nL for capillary separations. The low flow rates used in capillary chromatography permit the use of deuterated solvents. Unequivocal structural assignment of unknown chromatographic peaks is possible by two-dimensional stopped-flow capillary HPLC-NMR experiments.
    Zusätzliches Material: 14 Ill.
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  • 238
    Digitale Medien
    Digitale Medien
    Enhanced Resolution of Conjugated Linoleic Acid Isomers by Tandem-Column Silver-Ion High Performance Liquid Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 144-148 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Conjugated linoleic acid (CLA) ; silver-ion high performance liquid chromatography (Ag+-HPLC) ; cheese ; analysis ; silver-ion chromatography ; tandem-column Ag+-HPLC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---A commercial mixture of conjugated linoleic acid (CLA) isomers, reportedly consisting of six components, was recently resolved into 12 peaks attributed to CLA isomers using silver-ion high performance liquid chromatography (Ag+-HPLC). In this study, the coupling of two analytical silver-ion high performance liquid chromatography columns (tandem-column Ag+-HPLC) in series led to the enhanced resolution of CLA isomers. Many CLA isomers were baseline resolved and the pair 18 : 2 8,10 c/t and 18 : 2 7,9 c/t found in cheese products, was resolved for the first time. In this work, a similar commercial CLA mixture was separated into 16 peaks, while CLA isomers from cheese also gave rise to 16 peaks. As expected, the CLA isomers were separated into three geometric groups in the order trans,trans, cis/trans, and cis,cis. Semi-preparative Ag+-HPLC, followed by gas chromatography-mass spectroscopy of the dimethyloxazoline derivatives, was used to confirm the identity of the newly resolved positional CLA isomers. The double bond configuration of CLA isomers was established by gas chromatography-Fourier transform infrared spectroscopy. Two minor t,t CLA isomers found in cheese, presumably 18 : 2 t6t8 and 18 : 2 t13t15, were also separated. The CLA isomeric composition of 16 commercial cheese products was determined.
    Zusätzliches Material: 5 Ill.
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  • 239
    Digitale Medien
    Digitale Medien
    The Importance of Solvent Venting to Reduce Memory Effects with On-Line LC-GC-AED (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 159-163 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Multi-dimensional chromatography ; LC-GC ; AED ; memory effects ; fossil fuel ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---Conventional operation of the GC Atomic Emission Detector (AED) system involves backflushing of the microwave induced plasma (MIP) during the elution of small volumes of solvent from the GC column. When performing multi-dimensional, on-line LC-GC-AED, significantly larger solvent volumes are introduced into the system and must subsequently be removed. Thus solvent venting procedures are required and the backflushing of the plasma must be extended to facilitate solvent but not solute removal. This study demonstrates the significance of memory effects imparted upon the MIP of the AED if solvent venting is incomplete. Comparison of conventional GC-AED and multi-dimensional LC-GC-AED is made with respect to a fossil fuel sample.
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  • 240
    Digitale Medien
    Digitale Medien
    Multiresidue Analysis of Phenylurea Herbicides in Environmental and Drinking Water by Capillary Electrophoresis (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 171-176 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Micellar electrokinetic chromatography (MEKC) ; solid phase extraction (SPE) ; phenylurea(s) ; herbicide(s) ; monuron ; linuron ; diuron ; isoproturon ; monolinuron ; drinking water ; environmental water ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---The present paper describes the application of capillary electrophoresis in the micellar mode to the separation and quantitative determination of five phenylurea herbicides, viz. monuron, linuron, diuron, isoproturon, and monolinuron, in water samples. Using uncoated fused silica capillary and phosphate-borate buffer (pH 7.0) containing SDS, the five pesticides are resolved in less than 15 min and quantitatively determined by an ultraviolet detector at 244 nm. Method optimization and validation parameters are presented. Good linearity and repeatability were observed for all the compounds studied (correlation coefficients 0.999). The feasibility of the method developed was tested by simultaneous determination of these herbicides in environmental and drinking water samples at the minimum residue levels (MRLs) (0.1 μg/L) after solid-phase extraction (SPE) preconcentration procedure.
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  • 241
    Digitale Medien
    Digitale Medien
    Solid Phase Microextraction and GC-MIP-AED for the Speciation Analysis of Organomercury Compounds (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 181-182 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; microwave induced emission spectrometry ; speciation ; mercury ; SPME, headspace SPME ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---No abstract
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 242
    Digitale Medien
    Digitale Medien
    At-Line Solid-Phase Extraction Coupled to Capillary Electrophoresis: Determination of Amphoteric Compounds in Biological Samples (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 183-187 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Capillary electrophoresis ; interfacing ; sample treatment ; serum ; solid-phase extraction ; sulfonamides ; urine ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---No abstract
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 243
    Digitale Medien
    Digitale Medien
    Analysis of Mixtures of Fatty Acid Esters by Chromarod Chromatography/Flame Ionization Detection (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 191-194 
    Details
    ISSN: 0935-6304
    Schlagwort(e): TLC/FID ; simple and double migration ; triangle of solvent selectivity ; lipochemical media ; fatty acid esters ; esterification ; transesterification ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---No abstract
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 244
    Digitale Medien
    Digitale Medien
    Determination of 1,4-Dioxane in Toluene by Gas Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 201-204 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Capillary gas chromatography ; flame ionization detection ; solvent effects ; aqueous injection ; toluene analysis ; dioxane ; sample preparation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---A gas chromatographic method is presented for determining from 1 to 100 μg/mL of 1,4-dioxane in toluene with purities ranging from commercial to high-purity grades. This method relies on extracting 1,4-dioxane from toluene into water. The water extract is analyzed for 1,4-dioxane content by gas chromatography/flame ionization detection and a capillary column coated with a bonded polyethylene glycol stationary phase. Splitless injection is used to achieve a 1 μg/mL detection limit. Purging extracts with nitrogen after an initial analysis is suggested as an extract clean-up procedure and as a means to confirm the identification of 1,4-dioxane. However, for absolute identification of dioxane, gas chromatography/mass spectroscopy should be considered.
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  • 245
    Digitale Medien
    Digitale Medien
    Flow Rate and Velocity of Ideal Gas in a Capillary Column with Uniform Permeability (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 213-216 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Average velocity ; characteristic parameters ; flow rate ; high pressure drop ; low pressure drop ; outlet velocity ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: When the column pressure drop is high, the average velocity of a carrier gas is proportional to the square root of the outlet velocity and the flow rate. Characteristic velocity, flow rate and pressure - the boundary conditions between low and high pressure drop regions - are introduced. Previously derived equations for average velocity vs. outlet velocity were modified to include the flow rate and to become more suitable for the separate studies of the low and high pressure drop regions.
    Zusätzliches Material: 1 Ill.
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  • 246
    Digitale Medien
    Digitale Medien
    Determination of Green and Black Tea Composition by Capillary Electrophoresis (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 225-230 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Green tea ; black tea ; composition ; stability ; capillary electrophoresis ; MEKC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: No abstract
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
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  • 247
    Digitale Medien
    Digitale Medien
    High Speed Cryogenic Modulation - A Technology Enabling Comprehensive Multidimensional Gas Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 235-238 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Cryogenic modulation ; LMCS ; GC×GC ; multidimensional GC ; comprehensive gas chromatography ; petroleum analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: No abstract
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 248
    Digitale Medien
    Digitale Medien
    Heptakis(6-O-ethyl-2,3-O-pentyl)-β-cyclodextrin: A New Chiral Stationary Phases for Capillary GC (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 242-244 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Enantioselective gas chromatography ; 6-O-ethyl-2,3-O-pentyl-β-cyclodextrin ; essential oils ; carboxylic acids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---No abstract
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 249
    Digitale Medien
    Digitale Medien
    Determination of Amitraz in Cattle Dipping Baths by High-Performance Liquid Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 247-249 
    Details
    ISSN: 0935-6304
    Schlagwort(e): High performance liquid chromatography-ultraviolet detection (HPLC-UV) ; Amitraz ; cattle dipping bath ; pesticide ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---No abstract
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 250
    Digitale Medien
    Digitale Medien
    On-Line Coupled Liquid Chromatography - Gas Chromatography in the Analysis of Process Samples (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 261-264 
    Details
    ISSN: 0935-6304
    Schlagwort(e): On-line coupled LC-GC ; normal phase liquid chromatography ; process samples ; oxygenated compounds ; partially concurrent solvent evaporation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---Normal phase liquid chromatography-gas chromatography was used with on-column interfacing and partially concurrent solvent evaporation in the analysis of process samples. Samples were taken from reaction mixtures, where the solvent was toluene. The analytes were oxygenated compounds: methyl isobutyrate, methyl methacrylate, methyl α-formyl isobutyrate, and methyl β-formyl isobutyrate. The analytes were transferred from LC to GC using back-flush with a solvent mixture of pentane and diethyl ether. Linearity, repeatability, and transfer efficiency were determined for the method. The method was applied in the determination of the analytes of two different process samples. The results were in good agreement with results obtained by the gas chromatographic method currently in use for the analysis of the process samples.
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  • 251
    Digitale Medien
    Digitale Medien
    Determination of the Critical Micelle Concentration of Cationic Surfactants by Capillary Electrophoresis (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 265-270 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Critical micelle concentration ; cationic surfactant ; capillary electrophoresis ; tetradecyltrimethylammonium bromide ; dodecyltrimethylammonium bromide ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---The determination of the critical micelle concentration (CMC) of cationic surfactants by capillary electrophoresis was demonstrated. In this study, tetradecyltrimethylammonium bromide (TTAB) and dodecyltrimethylammonium bromide (DoTAB) were selected as cationic surfactants and propazine was chosen as test solute. In the evolution of the effective electrophoretic mobility of propazine as a function of surfactant concentration, a dramatic change in slope at a particular concentration is a good indication of the CMC of this surfactant. The CMC values determined experimentally were further confirmed by a curve-fitting approach. Simulation of the electrophoretic mobility curves as a function of surfactant concentration in both micellar electrokinetic chromatography and capillary zone electrophoresis using cationic surfactants as an electrolyte modifier was performed for propazine, and the intersection of these two mobility curves allowed us to precisely predict the CMC of the surfactant. The CMC values determined for TTAB and DoTAB are 1.6 ± 0.1 and 11.0 ± 0.1 mM, respectively, in the case of an electrolytic solution consisting of 70 mM phosphate buffer at pH 6.0. Moreover, the applicability of the electroosmotic mobility as a parameter for the determination of the CMC was examined.
    Zusätzliches Material: 6 Ill.
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  • 252
    Digitale Medien
    Digitale Medien
    A Unified Sample Preparation System for Extraction of Various Analyte/Matrix Combinations (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 271-275 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Supercritical fluid extraction ; enhanced solvent extraction ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---A supercritical fluid extraction/enhanced solvent extraction system (SFE/ESE) was used to remove polar and non-polar analytes from various matrices. Extraction of environmental pollutants from soil, additives from low density polyethylene, sulfa drugs from animal tissue, and drug from tablet was performed using both SFE and ESE. Results showed that a single instrumental system can be used to perform both ESE with organic solvents and SFE with carbon dioxide-based fluids. Each method has its own unique advantages and applications. The ability to carry out both solvent extraction and supercritical fluid extraction with one system has obvious economical advantages.
    Zusätzliches Material: 5 Ill.
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  • 253
    Digitale Medien
    Digitale Medien
    An Improved Interface for Coupling Solid-Phase Microextraction (SPME) to High Performance Liquid Chromatography (HPLC) Applied to the Analysis of Explosives (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 279-282 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Solid phase microextraction (SPME) ; SPME/HPLC interface ; C-8 refocusing unit ; explosives analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---No abstract
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 254
    Digitale Medien
    Digitale Medien
    Analysis of the Naturally Occurring Pesticide Rotenone by Capillary Gas Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 294-296 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Gas chromatography ; capillary ; fused silica ; rotenone ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: No abstract
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 255
    Digitale Medien
    Digitale Medien
    Isolation of Polychlorodibenzo-p-dioxins and Polychlorobiphenyls upon Deproteinization of a Serum Sample by HPLC with Restricted-Access Reversed-Phase Packing Materials (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 287-293 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Deproteinization ; polychlorobiphenyls ; polychlorodibenzo-p-dioxins ; restricted-access reversed-phase packings ; sample preparation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---No abstract
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 256
    Digitale Medien
    Digitale Medien
    Determination of Trichothecene Toxin (T2 Mycotoxin) in Aqueous Sample with Solid Phase Microextraction Technique Followed by Gas Chromatography with Flame Ionization Detection (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 424-426 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Mycotoxin ; T2 ; solid phase microextraction ; GC/FID ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---No abstract
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
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  • 257
    Digitale Medien
    Digitale Medien
    Preparation of On-Column Frits in Packed Fused Silica Capillaries by Sol-Gel Technology (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 438-442 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Capillary electrochromatography ; micro-HPLC ; preparation of on-column frits ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---Existing methods for preparing frits in packed fused silica capillaries as used for electrochromatography and micro HPLC are not applicable to all silica based packing materials and involve a high thermal stress for both the stationary phase and the fused silica tubing including the polyimide coating. A new procedure for the production of such on-column frits under mild conditions by a sol-gel type reaction of polydimethoxysiloxane (PDMOS) is described in this paper. Reaction conditions were established for optimum mechanical stability and high permeability of the frits. Frits produced in this manner showed no noticeable effect on the overall efficiency.
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  • 258
    Digitale Medien
    Digitale Medien
    Application of Temperature and Applied Voltage Programming in Micellar Electrokinetic Capillary Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 443-448 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Micellar electrokinetic capillary chromatography ; temperature programming ; applied voltage programming ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---Temperature and voltage programming modes were utilized to optimize selectivity and increase the eluting rate of strongly retained compounds in micellar electrokinetic chromatography. Separations obtained by applying temperature, voltage, and a simultaneous combination of temperature and voltage gradient in micellar electrokinetic capillary chromatography were compared with separations performed under isothermal and constant voltage conditions. A complete separation of all the constituents of the test mixture was only achieved in the temperature programming run and in a combination of temperature and voltage programming modes. Simultaneous variations of column temperature and applied voltage during a separation run, yielded a 30% reduction in the total analysis time when compared to a temperature gradient alone. Temperature programming and voltage programming modes may be the gradient methods of choice because of the considerable technical difficulties involved in performing linear solvent gradient elution in micellar electrokinetic chromatography.
    Zusätzliches Material: 7 Ill.
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  • 259
    Digitale Medien
    Digitale Medien
    Fast Temperature Programming in Gas Chromatography using Resistive Heating (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 459-464 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Fast gas chromatography ; gas chromatography ; resistive heating ; organophosphorus pesticides ; PAHs ; triazines ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---The features of a resistive-heated capillary column for fast temperature-programmed gas chromatography (GC) have been evaluated. Experiments were carried out using a commercial available EZ Flash GC, an assembly which can be used to upgrade existing gas chromatographs. The capillary column is placed inside a metal tube which can be heated, and cooled, much more rapidly than any conventional GC oven. The EZ Flash assembly can generate temperature ramps up to 1200°/min and can be cooled down from 300 to 50°C in 30 s. Samples were injected via a conventional split/splitless injector and transferred to the GC column. The combination of a short column (5 m×0.25 mm i. d.), a high gas flow rate (up to 10 mL/min), and fast temperature programmes typically decreased analysis times from 30 min to about 2.5 min. Both the split and splitless injection mode could be used. With n-alkanes as test analytes, the standard deviations of the retention times with respect to the peak width were less than 15% (n = 7). First results on RSDs of peak areas of less than 3% for all but one n-alkane indicate that the technique can also be used for quantification. The combined use of a short GC column and fast temperature gradients does cause some loss of separation efficiency, but the approach is ideally suited for fast screening as illustrated for polycyclic aromatic hydrocarbons, organophosphorus pesticides, and triazine herbicides as test compounds. Total analysis times - which included injection, separation, and equilibration to initial conditions - were typically less than 3 min.
    Zusätzliches Material: 7 Ill.
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  • 260
    Digitale Medien
    Digitale Medien
    Determination of Deuterated Phenylalanine and Tyrosine in Egg Protein by GCQ (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 465-468 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Amino acid ; stable isotope ; GC-MS ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---In order to study protein digestibility by means of noninvasive tracer techniques (stable isotopes), a representative oral tracer, i.e. a stable isotope labeled protein, is needed. Therefore, egg white containing L-[ring-2H5]phenylalanine and L-[ring-2H4]tyrosine was prepared. The aim of this study was to measure the isotopic enrichment of the labeled amino acids in the egg white. The use of a standard GC-MS, based on ion trap technology was found to be a reliable technique. The enrichment of L-[ring-2H5]phenylalanine and L-[ring-2H4]tyrosine, expressed in Molar Percent (MP) amounted to 23.2 MP and 2.8 MP respectively.
    Zusätzliches Material: 4 Ill.
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  • 261
    Digitale Medien
    Digitale Medien
    Development of a Methodology for the Identification of Volatiles in Industrial Adhesive Formulations by GC/MS with Manual Headspace Sampling (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 477-480 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Adhesives ; GC/MS ; headspace analysis ; poly(vinyl acetate) ; volatile organic compounds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---No abstract
    Zusätzliches Material: 2 Ill.
    Materialart: Digitale Medien
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  • 262
    Digitale Medien
    Digitale Medien
    High Resolution Separation of Non-Polar Lipid Classes by HPLC-ELSD Using Alumina as Stationary Phase (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 483-486 
    Details
    ISSN: 0935-6304
    Schlagwort(e): HPLC ; alumina ; evaporative light-scattering detection ; non-polar lipids ; wax esters ; sterol esters ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---This study describes the performance and capacity of alumina as stationary phase in an HPLC-ELSD (evaporative light-scattering detection) method optimized for the separation of the non-polar lipid classes hydrocarbons, wax esters, sterol esters, triacylglycerols, and sterols, including quantitative determination of these lipid classes in natural samples. By using gradient elution and constant equilibration times between injections, highly reproducible separations of triacontane, stearyl oleate, and cholesterol oleate were accomplished with a binary mobile phase system. Phase A contained 0.5% tetrahydrofuran in hexane and phase B 20% isopropanol and 20% tetrahydrofuran in hexane. The same system was also used to determine the non-polar lipid classes in a zooplankton sample, the major lipid class being wax esters, followed by triacylglycerols, sterol esters, sterols, and hydrocarbons. Substantial amounts of an unknown compound, possibly acylated glyceryl ethers, were also found. The equilibration time of alumina was relatively slow compared to a polyvinyl alcohol stationary phase used earlier by the authors and calibration curves for different lipid classes were more uniform and linear with alumina.
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  • 263
    Digitale Medien
    Digitale Medien
    Prediction of Migration Times of Organic Ions in Capillary Zone Electrophoresis (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 495-500 
    Details
    ISSN: 0935-6304
    Schlagwort(e): CZE ; mobility ratio ; migration time prediction ; mathematical model ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---The electrophoretic mobility ratio (R value) of any two ions is constant and independent of the capillary type and electrophoretic conditions if their electrical charges and hydration radii are constant. The use of strong acid salts and quaternary ammonium salts is therefore proposed for the determination of R values. Such analytes are called markers. The following determinations can be carried out: (i) the determination of the migration time corresponding to the electroosmotic flow (EOF) in any capillary under any electrophoretic condition by measuring the migration times of two markers in the condition studied (useful when the EOF is weak); (ii) the determination of the migration time of an analyte in any capillary by knowing the migration time of the markers in the capillary studied. If the pH is changed and the ionization of the analyte is pH dependent, the resulting migration time for the analyte can be calculated. The constancy of the mobility ratios of seven markers was checked experimentally at eight different pH values (between pH 3 and 10), at three temperatures, and for two buffer concentrations. The predicted and experimental migration times were also compared in two different types of capillaries.
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  • 264
    Digitale Medien
    Digitale Medien
    Possibilities and Limitations of Fast Temperature Programming as a Route towards Fast GC (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 509-513 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Fast GC ; fast temperature programming ; resistive heating techniques ; short columns ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---One possible way to speed up a gas chromatographic analysis is the application of fast temperature programming by using resistive heating techniques. With this heating technique programming rates up to 20° per second can be reached. A relative standard deviation of retention times better than 0.2% is obtained. Using fast temperature programming the analysis-times of a mineral oil sample, an industrial oligomer sample, and toxic compounds in diesel fuel have been reduced 5 to 20 times, compared to a standard temperature programmed analysis. In most cases resistive heating cannot be applied to reduce the analysis time of a complex sample. The use of fast temperature programming is preferable to the use of short columns and columns operated at above-optimum carrier gas velocities.
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  • 265
    Digitale Medien
    Digitale Medien
    Trace Determination of Organic Compounds in Water by Direct Enrichment in Multichannel Thick Film Silicone Rubber Traps with Capillary Gas Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 521-526 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Multichannel silicone trap ; water analysis ; flow rate ; methanol ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The application of Multichannel Silicone Rubber Traps for the direct analysis of organic compounds in water was studied. The optimum collection flow rate for a 10 mL sample was found to be ca. 150 μL·min-1. The effect of methanol on the retention power of the trap was evaluated. The addition of a methanol fraction of up to 40% to the water standards did not show any loss in collection efficiency. It was shown that the extraction of organic compounds from water with the multichannel trap is uncomplicated, i. e. methanol is not required to achieve accurate analyses, concentration of the sample onto the trap is by gravity flow, and excess water remaining in the multichannel trap after water extraction is removed by centrifugation. With the use of the multichannel silicone rubber trap a wide boiling point range of compounds were analyzed from aqueous samples at levels of 1-4 μg·L-1.
    Zusätzliches Material: 5 Ill.
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  • 266
    Digitale Medien
    Digitale Medien
    Improved Procedure for Single DB-XLB Column GC-MS-SIM Quantitation of PCB Congener Distributions and Characterization of Two Different Preparations Sold as “Aroclor 1254” (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 533-540 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Chlorobiphenyl congeners ; Aroclor 1254 ; DB-XLB phase ; GC-MS-SIM ; PCB 126 ; toxic equivalency ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---Complete PCB congener distributions in a panel of Aroclor mixtures were previously obtained by combining data from several HRGC systems. In that study quantitation of minor components may have been unreliable due to single level calibration against high levels of individual congener standards. Two lots of Aroclor 1254 had markedly different congener distributions. In this study, the design and performance of a congener-specific PCB analysis method employing GC-MS-SIM detection of congeners separated on a DB-XLB capillary column are discussed. Quantitation is carried out against a 6-level inclusive standard curve of a mixture of 144 congeners found in Aroclors. A separate procedure to measure trace levels of PCB 126 in Aroclors using the same system, combined with levels initially acquired for other congeners, facilitates estimation of TEQ values (Toxic Equivalencies of the PCB mixtures to 2,3,7,8-TCDD). PCB congener profiles of 15 Aroclor 1254 mixtures are presented. These profiles show that the less common, high TEQ variety of Aroclor 1254 was manufactured by an atypical, two-stage chlorination process that was apparently used during the final 1% of Aroclor 1254 production (ca. 1974-1976).
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  • 267
    Digitale Medien
    Digitale Medien
    Functionalized Polymeric Sorbents for Solid-Phase Extraction of Polar Pollutants (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 547-552 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Water analysis ; polar pollutants ; solid-phase extraction ; chemically-modified polymeric resins ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---This study assesses how the physical characteristics of styrene-divinylbenzene (PS-DVB) resins affect the extent to which they are modified when they are functionalized, and how they affect recoveries in on-line solid-phase extraction (SPE) of some polar phenolic compounds, pesticides, and metabolites from water samples which were analyzed by liquid chromatography and UV detection. For this purpose, three commercial PS-DVB resins with different physical characteristics (Amberchrom GC-161m and two different PLRP-S resins) were chemically modified by placing a hydrophilic group, an o-carboxybenzoyl moiety, on their surface; although the physical characteristics are different, the extent of modification did not vary significantly. The results from the SPE process with each sorbent were related to their physical and chemical properties. The polymers with higher surface area provided better recoveries. Moreover, the recoveries for these analytes were better with the chemically-modified polymers due to the higher polarity of these sorbents. The best recovery values were with the sorbent obtained from the chemical modification of Amberchrom GC-161m, the commercial sorbent with higher surface area. For instance, in the analysis of 50 mL of a sample of 2 μg L-1, the recovery of phenol was 40% with Amberchrom GC-161m and 65% with the chemically-modified Amberchrom GC-161m.
    Zusätzliches Material: 3 Ill.
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  • 268
    Digitale Medien
    Digitale Medien
    γ-Dithiolactones - Analytical and Sensory Characteristics (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 421-423 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Enantioselective gas chromatography ; 2,3-di-O-methyl-6-O-tert-butyldimethylsilyl-β-cyclodextrin ; 2,3-di-O-acetyl-6-O-tert-butyldimethylsilyl-β-cyclodextrin ; γ-dithiolactones ; olfactometry ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---No abstract
    Zusätzliches Material: 2 Ill.
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  • 269
    Digitale Medien
    Digitale Medien
    Determination of Biological Oxidative Stress Using High Performance Liquid Chromatography with Electrochemical Detection (HPLC-ECD) (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 429-437 
    Details
    ISSN: 0935-6304
    Schlagwort(e): HPLC ; nitrotyrosine ; nitrotocopherol ; analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---For three decades, high performance liquid chromatography has proven itself to be a powerful, flexible, and inexpensive tool for basic and clinical research. Recent advances in our understanding of disease have prompted a demand for more sensitive and selective methods of routine bioanalysis, particularly with respect to the determination of oxidative metabolites and biomarkers of oxidative stress. Multidimensional detectors utilizing coulometric arrays offer a solution to these research needs. The challenge to the bioanalyst is now to creatively apply HPLC-ECD technology to promising research and clinical enterprises.
    Zusätzliches Material: 9 Ill.
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  • 270
    Digitale Medien
    Digitale Medien
    Optimization and Parameter Study for Chiral Separation by Capillary Electrophoresis (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 449-453 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Capillary electrophoresis ; experimental design ; cyclodextrin ; chiral separation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---Orthogonal design and uniform design were used for the optimization of separation of enantiomers using 2,6-di-O-methyl-β-cyclodextrin (DM-β-CD) as a chiral selector by capillary zone electrophoresis. The concentration of DM-β-CD, buffer pH, running voltage, and capillary temperature were selected as variable parameters, their different effects on peak resolution were studied by the design methods. It was concluded that orthogonal design offers a rapid and efficient means for testing the importance of individual parameters and for determining the optimum operating conditions. However, for a large number of both factors and levels, uniform design is more efficient. The effect of addition of methanol and citric acid buffer on the separation of enantiomers was also examined.
    Zusätzliches Material: 5 Ill.
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  • 271
    Digitale Medien
    Digitale Medien
    Prototypical Test Substances for a Reversed Phase in a Retention Parameter Model (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 454-458 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Liquid chromatography ; reversed phase ; prototypical substances ; retention parameter model ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---A set of four prototypical substances (naphthalene, acetanilide, phenol, and benzonitrile) is selected from 26 different analytes used by Seibert and Poole for characterization of the retention behavior of 20 liquid chromatographic systems of a C18 reversed phase with methanol/water and acetonitrile/water as mobile phases. Retention data of 22 different analytes can be calculated from the retention data of the set of prototypical substances with a mean standard deviation of 5.4%. Two phase system maps similar to that suggested by Poole et al. are provided for an octadecylsiloxane-bonded silica sorbent with methanol and acetonitrile as cosolvents with water.
    Zusätzliches Material: 2 Ill.
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  • 272
    Digitale Medien
    Digitale Medien
    Determination of Organic Peroxides by Gas Chromatography with Cold On-Column Injection (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 475-476 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Organic peroxides ; gas chromatography ; FID ; cold on-column injection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---No abstract
    Zusätzliches Material: 1 Ill.
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  • 273
    Digitale Medien
    Digitale Medien
    Modifier and Additive Effects in the Supercritical Fluid Extraction of Pseudoephedrine Hydrochloride from Spiked-Sand and Suphedrine Tablets (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 469-474 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Supercritical fluid extraction ; SFE modifiers ; pseudoephedrine ; suphedrine ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---The effect of modifier and additive composition upon pseudoephedrine recovery from spiked-sand and Suphedrine tablets was examined. Recovery was shown to be dependent on CO2 density as well as on the addition of an ion pairing agent to the matrix. The presence of methanol in the extraction vessel prior to SFE was shown to play a significant role in the ion-pair extraction process. Recovery was also shown to be a function of ion-pairing reagent composition and concentration. The most successful recovery was obtained in the presence of 1-heptanesulfonic acid (HSA), sodium salt in methanol at a 5:1 molar ratio (reagent to drug). The increased extractability in the presence of ion-pairing reagent was attributed to reduced analyte polarity and analyte-matrix displacement. Alternatively, a matrix-spiked mixture of methanol and 1% water by itself was just as effective as a matrix-spiked mixture of methanol and HSA for attaining efficient extraction. Several in-cell (e. g. to the matrix) and in-line (e. g. to the fluid) modifiers were examined for the extraction of pseudoephedrine from Suphedrine tablets. The greatest pseudoephedrine recovery from Suphedrine tablets of 82% (7.0%) was achieved with 10% (l% H2O) methanol-modified CO2 in the presence of 400 μL of methanol (l% H2O). Finally AgCl tests and infrared analyses were performed on two tablet extracts. It was confirmed that even in the absence of any in-cell modifier, a small fraction of pseudoephedrine hydrochloride could be extracted.
    Zusätzliches Material: 5 Ill.
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  • 274
    Digitale Medien
    Digitale Medien
    Chiral Separation of Carboxymethyl Derivatives of Amines by Liquid Chromatography on Reversed-phase Silica Gel Coated with N-n-Dodecyl-L-hydroxyproline (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 487-489 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Carboxymethyl derivatives of amines ; dodecyl-L-hydroxyproline ; chelate ring ; chemiluminescence ; ruthenium complex ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---Carboxymethyl derivatives of amines containing a chiral α-carbon were separated into enantiomers by high-performance liquid chromatography using octadecylsilanized silica gel coated with N-n-dodecyl-L-hydroxyproline as the stationary phase and an aqueous solution containing copper(II) as the mobile phase. Detection was by post-column reaction involving derivatization to tertiary amine and chemiluminescence reaction of ruthenium bipyridine complex.
    Zusätzliches Material: 3 Ill.
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  • 275
    Digitale Medien
    Digitale Medien
    Temperature-Programmed Packed Capillary Liquid Chromatography Separation with Large Volume On-Column Focusing of Retinyl Esters (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 490-494 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Large volume injection ; packed capillary LC ; temperature programming ; retinyl esters ; vitamin A ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---A non-aqueous isocratic reversed-phase packed capillary high performance liquid chromatography method for the determination of retinyl esters, utilizing temperature programming and on-column focusing large volume injection, has been developed. The stationary phase material was C30, and the mobile phase consisted of acetonitrile-dichloromethane (70 : 30, v/v). A three-step temperature program, starting at 10°C for 10 min, then 1°/min to 30°C, and finally 2.5°/min to 70°C, was found most appropriate. Compared to an isothermal separation at 25°C, this temperature program provided improved peak resolution, enhanced peak shapes of the last eluting compounds, and a reduction of the overall elution time. A mass limit of detection of 27 pg was found with respect to retinyl palmitate, using UV detection with an “U” shaped flow cell at 327 nm. This corresponds to a concentration limit of detection of 2.7 pg/μL, when utilizing an injection volume of 10 μL. The concentration of retinyl palmitate in arctic seal liver samples was estimated to be 62.6 μg/g liver.
    Zusätzliches Material: 2 Ill.
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  • 276
    Digitale Medien
    Digitale Medien
    Separation of Positional Isomers on A, C- and A,D-Bridged Calix[6]arene as Stationary Phases in Capillary GC (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 679-682 
    Details
    ISSN: 0935-6304
    Schlagwort(e): A,C- and A,D-bridged calix[6]arene ; stationary phase ; capillary gas chromatography ; geometric and positional isomer separation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---A,C-Bridged (ACCX) and A,D-bridged isopropyldimethylsilylcalix[6]arene (ADCX) dissolved in OV-1701 were used as stationary phases in isothermal capillary gas chromatographic separation of some positional isomers. Retention factors and separation factors for the isomers were measured. The isomers investigated are well resolved on the two phases. Retention of all the solutes investigated is longer on ACCX than on ADCX. The longer retention on A,C-bridged calix[6]arene is probably due to extra inductive interactions of the solute molecule with the carbonyl moieties in the phase. Separation factors for closely eluting isomer pairs are similar on the two phases. This seems to indicate that the carbonyl moieties do not play an appreciable role in discriminating the isomer molecules on entering the cavity of the calixarene if the solute is retained by the inclusion process.
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  • 277
    Digitale Medien
    Digitale Medien
    Two-Dimensional Gas Chromatography. Concepts, Instrumentation, and Applications - Part 1: Fundamentals, Conventional Two-Dimensional Gas Chromatography, Selected Applications (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 647-665 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Two-dimensional GC ; statistical method of overlap ; petroleum ; fuels ; enviromental samples ; organochlorine compounds ; flavors ; aromas ; foods ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---The writer of this review published in 1978 a three-part article on two-dimensional gas chromatography in the first three issues of this journal [1]. The review was written at a time when capillary column GC was still in its infancy. Commercial columns were (essentially) unavailable and sample introduction into capillary columns was done exclusively in the split mode. Two-dimensional separations were explored in only a few laboratories. The limitations of capillary column technology made this exercise rather difficult. The introduction of fused silica capillary columns in the early eighties drastically changed the landscape in which gas chromatography was practiced. It took the chromatographic community just a few years to convert from packed columns to capillary columns. Instrumentation and accessories specifically designed for capillary column use came onto the market. This writer had great hopes that the revolution in capillary column GC would be mirrored in the development of instrumentation for Two-Dimensional Gas Chromatography. This never materialized. On the contrary, tentative steps taken by a few manufacturers and suppliers of chromatographic equipment fizzled out. It was perhaps the introduction of relatively inexpensive and user friendly GC/MS instrumentation, in combination with nearly indestructible fused silica capillary columns that took away the incentive to develop commercially viable Two-Dimensional Gas Chromatography. Much of the thinking went like this: why insist on good chromatography if mass spectrometry can do the job without the need for complete separation. Some progress in the further development of conventional Two-Dimensional Gas Chromatography has certainly been made over the last 20 years but there has not been a great deal of excitement. Applications have also been relatively sparse and they are limited to just a few areas. Science does not remain static and chromatography is no exception. Progress in gas chromatography is driven by new technology and ideas. Substantial improvements in two-dimensional GC were not forthcoming until Phillips and his research group introduced and implemented an entirely new form of Two-Dimensional Gas Chromatography, called comprehensive two-dimensional GC, or GC×GC. This breakthrough occurred only in 1991 [2]. It does take some time before scientists change attitudes and habits. There is always a time lag between the introduction of new technology and its general acceptance. The public's attitude toward comprehensive Two-Dimensional Gas Chromatography is probably no exception. The number of scientists who are actively pursuing this new branch of gas chromatography is still very small. It is often a single individual who carries the torch. J.B. Phillips' name is synonymous with comprehensive Two-Dimensional Gas Chromatography. He is not only its inventor and proponent but his fertile mind has initiated research in other related areas. Sadly, he passed away shortly before this review was written. This contribution is dedicated to his memory.
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  • 278
    Digitale Medien
    Digitale Medien
    Automated On-Line GPC-GC-FPD Involving Co-Solvent Trapping and the On-Column Interface for the Determination of Organophosphorus Pesticides in Olive Oils (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 17-23 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Coupled GPC-GC ; gel permeation chromatography ; on-column interface ; co-solvent trapping ; gas chromatography ; large volume injection ; organophosphorus pesticides ; olive oil ; automation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---The robustness of an automated on-line GPC-GC-FPD method for the determination of Organophosphorus (OP) Pesticides in olive oil has been significantly improved, now allowing a routine operation. The original GPC-GC transfer technique employed a loop type interface with an early vapor exit and co-solvent trapping. Shooting, caused by boiling delay and malfunctioning of the solvent vapor exit during the transfer of the 3 mL solvent fraction to the retention gap, resulted in insufficient focusing of the OP-pesticides. In this interfacing concept, the GPC fraction is introduced directly into the carrier gas stream during a certain time interval using the Dualchrom pressure- and flow regulation, resulting in a very stable transfer. The interface now basically corresponds to an on-column interface with flow regulation. Via a Pyrex glass door behind the GC-oven door it can be seen that the liquid flow is broken up into alternating gas-liquid segments by the carrier gas flow during transfer. This avoids shooting in the retention gap and broadens the temperature range for successful transfer. By using a smaller sized GPC column the solvent fraction transferred was reduced to 1.3 mL. Methyl acetate/cyclopentane and the co-solvent n-nonane were selected for their lower boiling points. The modified method is very robust and has been applied to the analysis of 28 different OP-pesticides in olive oil with an overall detection limit of 0.002 mg/kg. Routinely 24 h of unattended operation is possible with a cycle time of 75 min.
    Zusätzliches Material: 6 Ill.
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  • 279
    Digitale Medien
    Digitale Medien
    Investigation into the Formation of Bubbles in Capillary Electrochromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 29-32 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Capillary electrochromatography ; electroosmotic flow ; frit ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The formation of bubbles in capillary electrochromatography (CEC) is well documented: possible origins include Joule heating and variations in EOF velocity on passing from the stationary phase through the frit and into the open tube. Methods for the prevention of bubble formation are discussed which are confirmed by experimental results. Using frit lengths varying from 1 mm to 6 mm it is shown how frit length is directly related to the likelihood of bubble formation and how this is affected by applied voltage. It is shown that the change in applied voltage across a capillary affects the formation of bubbles and also that rebonding octadecylsilane (ODS) onto the silica frit after formation of the frit can minimize the formation of bubbles and how this effects the chromatography. A method is also described for increasing the robustness of silica capillaries using a column coupler along with modifications made to conventional capillary electrophoresis equipment to cater for CEC.
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  • 280
    Digitale Medien
    Digitale Medien
    Determination of Dihydroxybenzenes in Plastic Food Packaging Materials and in Food Simulating Liquids Using Capillary Electrophoresis (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 39-42 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Capillary electrophoresis ; CE ; chemical migration ; food contact plastics ; dihydroxybenzenes ; packaging ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---A capillary electrophoresis method has been developed to determine 1,2-dihydroxybenzene and 1,3-dihydroxybenzene in the food simulants distilled water, 3% acetic acid, 15% ethanol, and olive oil. Both substances, used as monomers and additives to make food packaging plastics, could be analyzed within 15 min. The 1,4-dihydroxybenzene isomer was unretained and eluted with the electroosmotic flow, and so the CE method can give only a semi-quantitative estimate of this isomer if it is present as a migrant. The analytical recovery for the 1,2- and 1,3-isomers from spiked simulants was good at 87% to 98% except for 1,2-dihydroxybenzene which could only be recovered to the extent of 58% from olive oil. Calibration graphs were linear and the limit of detection for each substance was 0.6 mg/kg, which is well below migration limits for these substances. It is concluded that CE offers a rapid and reliable analysis for the control of migration from plastics intended for food contact which employ 1,2-dihydroxybenzene or 1,3-dihydroxybenzene during manufacture, and offers a screening method for 1,4-dihydroxybenzene migration.
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  • 281
    Digitale Medien
    Digitale Medien
    Injection by Programmed Temperature Vaporization Injection (PTV) of Gaseous Samples for Gas Chromatography - Atomic Emission Spectrometry (GC-AED) (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 47-51 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Programmed temperature vaporization (PTV) ; GC-AED ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---Programmed temperature vaporization injection (PTV) coupled to gas chromatography and atomic emission detector (AED) has been studied for large volume injection of gaseous samples. As examples of the effectiveness of the technique, the results of the analysis of a series of headspace samples of foods such as garlic and onion, and of landfill gases are presented. The volumes of gaseous samples reconcentrated varied from a few milliliters up to liters depending on analyte dilution, through focusing onto a sorbent trap, then rapid liberation into the GC-AED system by programmed thermal desorption. Despite the high carrier gas flow rates associated with direct PTV-GC, AED performance and sensitivity were unaffected. The detailed elemental information obtained from the PTV-GC-AED analyses was confirmed using a PTV coupled to a gas chromatograph with ion trap detector mass spectrometer as detector (PTV-GC-ITD/MS).
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  • 282
    Digitale Medien
    Digitale Medien
    Investigation into the Effects of Sample Dissolving Solvents and Sample Matrices on the Separations Obtained in Capillary Electrophoresis. Part II. MECC (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 55-58 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Micellar electrokinetic capillary chromatography ; sample dissolving solvent ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 2 Ill.
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  • 283
    Digitale Medien
    Digitale Medien
    Separation of Regioisomers of Substituted Bromoindoles of Pharmaceutical Interest by RP-HPLC and Capillary Electrophoresis Based on Interaction with Sulfobutyl Ether-β-cyclodextrin (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 59-62 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Sulfobutyl ether-β-cyclodextrin ; micellar electrokinetic chromatography ; separation of regioisomers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 5 Ill.
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  • 284
    Digitale Medien
    Digitale Medien
    Determination of the Specific Migration of DEHP into Food Simulants Using High Performance Liquid Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 70-72 
    Details
    ISSN: 0935-6304
    Schlagwort(e): HPLC ; di(2-ethylhexyl) phthalate ; migration ; foods and food simulants ; PVC cling film ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Ill.
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  • 285
    Digitale Medien
    Digitale Medien
    Capillary Electrophoretic Identification of Commercial Gelling Agents (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 79-82 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Capillary electrophoresis ; thickeners ; monosaccharides ; PMMA capillaries ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---Gelling agents based on polysaccharides have become extremely important in the food industry. As more and more products like soups and sauces have become available in lyophilized form, thickeners have to be added to give a controlled consistency to the finished meal. A capillary electrophoretic method has been developed to investigate the monosaccharide composition of hydrolyzed thickeners. 2-Aminoanthracene was used as a derivatization reagent to allow sensitive fluorescence detection. This system was applied to a set of standard thickeners as well as to food samples.
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  • 286
    Digitale Medien
    Digitale Medien
    GC Analysis of Organic Acids and Phenols Using On-Line Methylation with Trimethylsulfonium Hydroxide and PTV Solvent Split Large Volume Injection (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 83-88 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Large volume injection ; programmed-temperature vaporizer ; organic acids ; phenols ; derivatization ; trimethylsulfonium hydroxide ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---The combination of on-line methylation using trimethylsulfonium hydroxide with large volume injection of 100 μL was evaluated for the analysis of organic acids and phenols in water. Solvent split injection was applied with complete evaporation of the solvent before analytes were transferred onto the GC column. Despite complete solvent removal, losses were very low compared to conventional splitless injection even for volatile acidic compounds such as propionic acid and phenol. This is explained by intermediate formation of low volatility trimethylsulfonium salts of the analytes which were held in the injector for long evaporation times of up to 10 min, if the evaporation temperature was as low as 10°C. Using a simple liquid/liquid extraction procedure, volatile fatty acids, dicarboxylic acids, benzoic acids and phenols could be detected in 5 mL of water at concentrations of 0.04-0.1 μmol/L with GC/MS in full scan mode. Lactic, pyruvic, and also malonic acids could only be detected at higher levels because of their limited extractability from water as well as their poorer methylation yields. The method provides an easy way to sensitively detect acidic compounds of medium to high volatility in water. It was applied for screening of organic acids and phenols in batch cultures of anaerobic bacteria of which one example is shown.
    Zusätzliches Material: 4 Ill.
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  • 287
    Digitale Medien
    Digitale Medien
    Study on the Performance of Three Different Capillary Gas Chromatographic Analyses in the Evaluation of Milk Fat Purity (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 97-102 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Capillary GC ; milk fat purity ; chemometrics ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---The adulteration of milk fat with foreign fat has been and still is a major concern in the dairy industry. Milk fat purity is currently evaluated by triglyceride analysis by using the Official EU method. The detection limit of the various vegetable and animal fats ranges between 4 and 6%. This research was carried out to verify whether it is possible to decrease the detection limits of beef tallow, which is the most widely used adulterating animal fat. For this purpose, determinations of diglycerides and 3,5-cholestadiene, together with the Official EU method, were applied both to several samples of pure milk fat and to mixtures of milk fat with different percentages of beef tallow. The best results were obtained combining the data deriving from the three determinations by multivariate statistical techniques; in particular, the statistical model obtained by the UNEQ technique seems to be able to decrease the detection limit of beef tallow from 5.2 to 2%. The diglyceride and 3,5-cholestadiene evaluation, combined with the Official EU method for triglycerides, can be usefully applied both to detect small additions of beef tallow and to demonstrate the adulteration of milk fat samples showing results close to the detection limit of the official method.
    Zusätzliches Material: 7 Ill.
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  • 288
    Digitale Medien
    Digitale Medien
    Solid-phase Microextraction of Volatile Polar Compounds in Water (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 109-115 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Solid-phase microextraction ; capillary gas chromatography ; volatile polar compounds ; water matrix ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---A method was developed for the analysis of volatile polar compounds in a water matrix using open cap vials Solid Phase Micro-Extraction (SPME) and Capillary Gas Chromatography (CGC). Both SPME techniques - direct sampling and headspace - were tested. Optimization of experimental conditions - exposure time, desorption time, with headspace SPME in addition the influence of the temperature and ionic strength of the sample solution on compound sorption, and finally GC response - were investigated. The analytes were extracted by directly immersing the 85 μm polyacrylate fiber in the aqueous sample or in the headspace. The linear range of the preconcentration process and the precision were examined. The amount of polar analytes sorbed on the fiber was determined and was found to be concentration dependent; it amounted to 0.014-0.64% in the concentration range of 0.00425-425 ppm studied in aqueous solution for direct sampling SPME and to 0.011-2.76% for solutions of concentration 0.0425-255 ppm for headspace SPME. The limits of determination were ascertained. Headspace SPME was applied to the analysis of real-life samples.
    Zusätzliches Material: 5 Ill.
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  • 289
    Digitale Medien
    Digitale Medien
    Analysis of Aliphatic Amines by Micellar Electrokinetic Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 126-128 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Micellar electrokinetic chromatography ; capillary electrophoresis ; amines ; cyclodextrins ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 290
    Digitale Medien
    Digitale Medien
    Drug Monitoring in Human Plasma by Capillary Gas Chromatography Coupled with Atomic Emission Detection. Potential and Limitations (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 123-125 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Capillary gas chromatography (GC) ; atomic emission detection (AED) ; human plasma ; drug monitoring ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 291
    Digitale Medien
    Digitale Medien
    Development and Validation of a Reversed-Phase Liquid Chromatographic Method for Analysis of Theophylline in Human Plasma (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 131-132 
    Details
    ISSN: 0935-6304
    Schlagwort(e): RP-HPLC ; theophylline ; asthma ; apnea ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 1 Ill.
    Materialart: Digitale Medien
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  • 292
    Digitale Medien
    Digitale Medien
    Semi-continuous High Speed Gas Analysis of Generated Vapors of Chemical Warfare Agents (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 153-158 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Vapor analysis ; nerve agents ; sulfur mustard ; data acquisition ; automation ; valve injection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---A method is presented for the continuous analysis of generated vapors of the nerve agents soman and sarin and the blistering agent sulfur mustard. By using a gas sampling valve and a very short (15 cm) column connected to an on-column injector with a “standard length” column, the system can either be calibrated or used for performing high speed gas analyses. When using a flame ionization detector, the detection limit was ca. 100 ppb (ca. 0.5-1.0 mg/m3). This technique is applied in inhalation toxicokinetic studies of nerve agents and mustard gas in the guinea pig.
    Zusätzliches Material: 6 Ill.
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  • 293
    Digitale Medien
    Digitale Medien
    Capacity of Uncoated 0.53 mm i.d. Pre-Columns for Retaining Sample Liquid in the Presence of a Solvent Vapor Exit (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 149-152 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Large volume on-column injection ; flooded zone ; capacity of 0.53 mm i. d. precolumns ; solvent trapping ; solvent vapor exit ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---0.53 mm i. d. uncoated precolumns of about 10 m in length followed by a solvent vapor exit have become a standard set-up for large volume on-column injection. It went unnoticed, however, that the introduction of a vapor exit requires two modification of previous working guidelines. First, the capacity of the precolumn to retain sample liquid is increased by a factor of 2.3-3 as a result of the around 100 times higher carrier gas flow rate. Secondly, it must be considered that this gain in retention of liquid is lost again upon closure of the exit: as the gas flow rate is reduced to a few mL/min, the layer of the residual sample liquid expands about 2.3-3 times. Hence, closure should occur late, and a section of the precolumn must be assigned for this secondary spreading.
    Zusätzliches Material: 3 Ill.
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  • 294
    Digitale Medien
    Digitale Medien
    Large Surface Area Divinylbenzene Copolymers for Size Exclusion Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 63-66 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Divinylbenzene copolymers ; exclusion limit ; size exclusion chromatography ; surface area ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
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  • 295
    Digitale Medien
    Digitale Medien
    A New Cell for Single Sided Headspace Sampling and Evaluation of Barrier Function in Laminated Paperboard (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 164-170 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Food packaging ; functional barrier ; gas chromatography ; laminated paperboard ; mass spectrometry ; single sided headspace ; paperboard ; plastic film ; polymer film ; test cell ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---A new cell for single sided headspace sampling has been developed for the analysis of volatile organic compounds from food packaging paperboard and laminated paperboard. The cell, which samples the volatile organic compounds over a selected surface, is useful for determining the barrier function of laminated paperboards with respect to volatile compounds. The analysis of volatile organic compounds is carried out by purge and trap capillary gas chromatography in combination with mass spectrometric detection and compound identification. The new sampling cell was constructed to facilitate specific analysis of organic compounds from only one side of a laminated paperboard. The construction and the operating principles of the new sampling device are described. The repeatability of the single sided headspace procedure was found to be quite good. Relative standard deviations of about 5-7% were obtained for the major compounds quantified in replicate headspace analyses of a laminated paperboard. The volatile compounds released from the inner side of a food packaging paperboard sample with different surface composition on the two sides were determined. The barrier function against volatile organic compounds of some laminated paperboards was investigated employing the new headspace cell.
    Zusätzliches Material: 7 Ill.
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  • 296
    Digitale Medien
    Digitale Medien
    HPLC Control of an Alkyl Glycoside Synthesis (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 188-190 
    Details
    ISSN: 0935-6304
    Schlagwort(e): LC stationary phases ; porous graphitic carbon ; surfactant ; alkyl glycosides ; glycosides ; evaporative light scattering detection ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---No abstract
    Zusätzliches Material: 3 Ill.
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  • 297
    Digitale Medien
    Digitale Medien
    Quantitative Determination of BTEX and Total Aromatic Compounds in Gasoline by Comprehensive Two-Dimensional Gas Chromatography (GC×GC) (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 195-200 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Multi-dimensional gas chromatography ; comprehensive two-dimensional gas chromatography ; GC×GC ; BTEX ; aromatics ; reformulated gasoline ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---Comprehensive two-dimensional gas chromatography (GC×GC) has been applied to the quantitative analysis of benzene, toluene, ethylbenzene, xylenes (BTEX), and all heavier aromatic compounds in gasoline. The two-dimensional chromatographic separation used volatility selection on the first-dimension column and polarity selection on the second-dimension column. In the resulting GC×GC chromatogram, aromatic species were resolved from other compound classes. Moreover, structurally related aromatics were grouped in a manner that facilitated identification and integration. The response of a flame ionization detector to each major aromatic group in gasoline was calibrated using internal standards. Quantitation produced results directly comparable with ASTM standard methods. The present GC×GC method can be expanded to analyze other gasoline components.
    Zusätzliches Material: 1 Ill.
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  • 298
    Digitale Medien
    Digitale Medien
    Membrane Extraction Combined with Thermodesorption/Gas Chromatography and Mass Selective Detection for the Analysis of Volatile Organic Compounds in Water (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 205-212 
    Details
    ISSN: 0935-6304
    Schlagwort(e): Membrane extraction ; hollow fiber membrane ; thermodesorption ; GC-MS ; volatile organic compounds ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---The range of application of a commercial thermodesorption-cryofocussing unit connected to a gas chromatograph/mass selective detector was extended to water analysis by using it in conjunction with membrane extraction. A flow of nitrogen passes through a silicone hollow fiber immersed in the water sample and extracted volatile organic compounds are enriched in a sorption tube mounted on top of the extraction cell. The sorption tube is then placed in the thermodesorption unit and analyzed by GC/MS. The optimal extraction parameters of this combined method were found to be 30 min extraction at 20°C with a stirring speed of 1,250 rpm and a flow rate of 100 mL/min nitrogen using a silicone hollow fiber of 0.3 m length. Under these conditions the reproducibility of the method was 5.2-10.5% RSD. The linear dynamic range of the optimized method spans three orders of magnitude and detection limits were found to be 0.02-0.1 μg/L for cis/trans-1,2-dichloroethene, benzene, trichloroethene, chlorobenzene, bromobenzene, ethylbenzene, 1,1,2,2-tetrachloroethane, and 1,2/1,4-dichlorobenzene. The method was found to be suitable for compounds with boiling points up to 220°C as memory effects increased considerably from dichloro- to hexachlorobenzene. Highly contaminated groundwater samples were analyzed. Quantitative results corresponded well with those achieved with conventional headspace-GC/FID.
    Zusätzliches Material: 10 Ill.
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  • 299
    Digitale Medien
    Digitale Medien
    Determination of Phenolic Compounds in Artemisia capillaris (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 222-224 
    Details
    ISSN: 0935-6304
    Schlagwort(e): High-performance liquid chromatography ; Artemisia capillaris ; phenolic compounds separation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---No abstract
    Zusätzliches Material: 2 Ill.
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  • 300
    Digitale Medien
    Digitale Medien
    New Stationary Phase Prepared by Immobilization of a Copper-Amine Complex on Silica and Its Use for High Performance Liquid Chromatography (1999)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 22 (1999), S. 103-108 
    Details
    ISSN: 0935-6304
    Schlagwort(e): HPLC ; stationary phase ; copper-amine complex ; aromatic amines ; polyaromatic hydrocarbons ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: ---Chromatographic silica (10 μm) was chemically modified with the silylating agent: [3-(2-aminoethyl)aminopropyl]trimethoxysilane (AEAPTS). The reaction product was characterized by elemental analysis and infrared and 13C and 29Si NMR spectra. The chemically modified silica was treated with Cu(II) in methanol medium. This cation was strongly adsorbed through complexation by the pendant ethylenediamine groups attached to the silica surface. The complex formed on the silica surface was shown to be stable in both aqueous and non-aqueous media. The aim of Cu(II) immobilization is to use this new material as a stationary phase in High Performance Liquid Chromatography (HPLC). Separations of synthetic mixtures of aromatic amines and of polyaromatic hydrocarbons were undertaken using 150×3.9 mm HPLC columns packed with the modified silica, with and without copper ions, to follow the influence of the cation on the chromatographic separation and to verify the efficiency of the new stationary phase for HPLC.
    Zusätzliches Material: 6 Ill.
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