Quantitative structure-retention relationships in comparative studies of behavior of stationary phases under high-performance liquid chromatography and capillary electrochromatography conditions.

Quantitative structure-retention relationships (QSRR) have been employed in studying the molecular mechanism of chromatographic separations under pressure- (HPLC) and electro-driven (CEC) conditions. Logarithms of retention factors corresponding to zero percent of organic modifier in aqueous eluent, log k(w), were determined on eight reversed-phase stationary phases under both HPLC and CEC conditions at similar eluent flow velocities. QSRR equations describing log k(w) in terms of linear solvation energy relationship (LSER) parameters of analytes, in terms of simple structural descriptors acquired by calculation chemistry, and in terms of logarithms of n-octanol-water partition coefficients, were derived.

Characterisation of reversed-phase stationary phases for the liquid chromatographic analysis of basic pharmaceuticals by thermodynamic data.

This paper describes the characterisation of reversed-phase liquid chromatography (RPLC) columns using thermodynamic measurements. Retention versus 1/T data were used to construct Van't Hoff plots. The slope of these plots indicates the standard enthalpy of transfer of the analyte from the mobile to the stationary phase.

Sorptive sample preparation -- a review.

Most sample-enrichment procedures currently available rely on adsorption of the analytes of interest by a suitable adsorbent material. Although good performance can be obtained for many practical problems, in some cases the applicability of adsorptive sample preparation falls short, particularly for the enrichment of polar and/or high-molecular-weight compounds, especially in combination with thermal desorption. Because of the very strong retention of adsorbent materials, undesired effects such as incomplete desorption and artifact formation are observed.

Endgroup-based separation and quantitation of polyamide-6,6 by means of critical chromatography.

Polyamide-6,6 is a polycondensation product from the two monomers adipic acid and 1,6-hexamethylenediamine. Depending on the reacted amount of these monomers, different ratios of amine and carboxylic acid endgroups can be formed. Besides linear chains, cyclic polyamides will also be formed.

Analysis of linear and cyclic oligomers in polyamide-6 without sample preparation by liquid chromatography using the sandwich injection method. III. Separation mechanism and gradient optimization.

The first six linear and cyclic oligomers of polyamide-6 can be quantitatively determined in the polymer using HPLC with the sandwich injection method and an aqueous acetonitrile gradient. In this final part of the triptych concerning the determination of the oligomers in polyamide-6, the irregular elution behavior of the cyclic monomer compared to the cyclic oligomers was investigated. We also optimized the separation of the involved polyamide oligomers, with respect to gradient steepness, stationary phase, column temperature and mobile phase pH.