Showing papers in "Journal of Chromatography A in 1993"

TL;DR: In this paper, the degree of separation of the d and l enantiomers of PheNHPh (α value) is used to establish the influence of polymer morphology on polymer performance.

TL;DR: The purpose of this review is to shed some light on the complex properties of zirconia's surface chemistry in order to better understand its behaviour under chromatographic conditions and shows that the main difficulty in achieving a wider variety of applications is probably the lack of knowledge and poor understanding of zIRconia’s surface chemistry.

TL;DR: In this article, the chiral recognition properties of a cellulase (cellobiohydrolase I) were used to identify the isomers and peaks with satisfactory symmetry of β-blockers.

TL;DR: In this paper, the observed chromatographic response for organophosphorus pesticides in extracts from milk and butterfat is shown to be matrix dependent, and the preferred method of calibration is to use matrix standard solutions prepared by adding known amounts of organoproporus pesticides to residue-free sample matrix.

TL;DR: In this article, different priority lists of pesticides in water from the European Economic Community (EEC) and the US Environmental Protection Agency (EPA) in water are listed and discussed, and the main aims of the different approaches are the development of screening methods for pesticides and their transformation products in water, the achievement of low limits of detection, especially in the case of the EEC Drinking Water Directive which sets a limit of 0.1 μg/l for individual pesticides.

TL;DR: A rapid fully automated method for the determination of amino acids is described based on high-performance liquid chromatography and pre-column o-phthaldialdehyde derivatization and the coefficient of variation for the peak areas measured was below 3%, both in aqueous standards and in plasma.

TL;DR: A method for the identification of secondary aromatic lichen substances using high-performance liquid chromatography (HPLC) with reversed phase columns, gradient elution and benzoic and solorinic acids as standards has been developed as discussed by the authors.

TL;DR: In this article, an equilibrium model has been developed to describe the pH and cyclodextrin concentration dependence of the electrophoretic mobilities as well as the c, and the equilibrium model is used to describe both pH and c.

TL;DR: In this paper, the effects of process variables such as concentration of displacement agent, flow-rate and gradient slope on HPMC separations in the ion exchange, hydrophobic interaction and reversed phase modes were studied using model protein mixtures.

TL;DR: The dependence of solute retention (k′) on mobile phase composition (%B) for binary-solvent mixtures A-B is reviewed and compared with various empirical and theoretical equations that have been proposed for this relationship as discussed by the authors.

TL;DR: The experiments show that the entanglement threshold is a useful parameter in predicting a range of HEC concentrations which will separate certain DNA fragments for a given HEC molecular weight, however, the presence of a fully entangled network is not a prerequisite for separation.

TL;DR: In this article, the authors presented data for the partition coefficients (n-octanol-water) (Pow) of 221 pesticides and pesticide metabolites with their method of derivation and source.

TL;DR: Cyclodextrin (CD)-modified micellar electrokinetic chromatography was applied to the separation of closely related aromatic compounds and enantiomeric separations using CD together with sodium dodecyl sulphate (SDS) as mentioned in this paper.

TL;DR: A model describing the events controlling binding and selectivity as a function of pH is proposed, suggesting that a simple cation-exchange mechanism controls the retention in this system.

TL;DR: The NIST experience in the use of liquid chromatography for the determination of polycyclic aromatic hydrocarbons (PAHs) in environmental samples is summarized in this paper, including selection of the appropriate column, approaches to analyzing complex PAH mixtures, and accurate quantification of PAHs.

TL;DR: In this article, the authors review both the chromatographic methods used for these estimations, their successes and failures, and discuss pertinent solution thermodynamics of the partitioning of small molecules between bulk phases, such as octanol and water, and between a bulk phase and an interphase.

TL;DR: In this paper, a review of the theoretical background of QSRR and its application in the search for new reliable and precise descriptors of the structures of solutes of relevance to their properties, including properties other than chromatographic, e.g., bioactivity.

TL;DR: This review will address the theoretical foundation of the chromatographic method for the estimation of partition coefficients, with an emphasis on the origins of anomalous retention behavior.

TL;DR: A liquid chromatographic (LC) method has been developed for the quantitative measurement of the six major carotenoids in human serum (lutein, zeaxanthin, beta-cryptoxanthin), as well as retinol, retinyl palmitate, alpha-tocopherol, gamma-tocoperol, and delta-tocouserol).

TL;DR: An HPLC method using a normal-phase silica column and a gradient of dichloromethane-methanol-formic acid water mixtures as the eluent was developed to separate procyanidins on a molecular mass basis, without derivatization.

TL;DR: Polyvinylmethylsiloxanediol (50% vinyl) was synthesized and combined with a cross-linker for static coating onto fused-silica columns that yielded successful open tube and polymer network separations of proteins, peptides and DNA molecules.

TL;DR: Series of linear malto-oligosaccharides were found particularly suitable for both the study of the effect of the operating conditions on the separation and the investigation of the relationship between the electrophoretic mobility and the molecular size of the homologues.

TL;DR: In this article, a review of the factors that affect retention and selectivity with alkyl-modified sorbents, particularly for the separation of solutes with well defined, rigid structure (e.g., polycyclic aromatic hydrocarbons), is presented.

TL;DR: There is an optimum concentration of MeBCD for separation for each of the beta-blockers, the magnitude of which could be ranked by the use of a mathematical model and log P data--an indication of the hydrophobicity of the molecule.

TL;DR: The mechanisms of solid-phase extraction, types of sorbents and their application to multi-residue pesticide analysis are reviewed and a solution to environmental problems is offered.

TL;DR: In this paper, the resolution of a pair of enantiomers in chiral capillary electrophoresis (CE) is described by the use of a simple model, which shows the importance of maximising the electrophoretic mobility difference between the two enantiomer, and also the influence of electroosmotic mobility.

TL;DR: In this paper, an electrolyte system based on pyromellitic acid is proposed for direct photometric detection of anions, where the ability to modify the electrophoretic mobility of pyromelliitic acid as a function of ph provides flexibility in matching electrophoreic mobilities of analytes.

TL;DR: In this article, a new chromatographic hydrophobicity index (ϕ 0 ) is suggested as a measure of the lipophilic character of compounds in reversed-phase high-performance liquid chromatography (RP-HPLC).

TL;DR: The pH-zone refining countercurrent chromatography (pH-ZRC) as discussed by the authors is a countercurrent method that utilizes two immiscible solvent phases, one being acidic and one being basic, to partition solutes in contiguous, well-resolved, rectangularly shaped peaks in order of their partition coefficients.

TL;DR: Capillary electrophoresis is investigated for the determination of thermodynamic pKa measurements at low solute concentrations, a current limitation of potentiometric titrations as mentioned in this paper, which relies on measuring the ionic mobility of the solute as a function of pH.