Suppression of chiral recognition of 3-hydroxy-1,4-benzodiazepines during micellar electrokinetic capillary chromatography with bile salts.

During the development of a micellar electrokinetic chromatographic screening method for 1,4-benzodiazepines, peak splitting and broadening were observed for some 3-hydroxy-1,4-benzodiazepines (oxazepam, lorazepam, temazepam and lormetazepam). This phenomenon occurred when the micellar phase consisted of bile salts and can be ascribed to the chiral nature of these surfactants. As the bile salts were applied in order to reduce the capacity factors to an appropriate level, enantiomer separation was not an objective and even disturbing. By increasing the analysis temperature, the chiral recognition of these compounds could be suppressed.

Application of micellar electrokinetic chromatography to the quality control of pharmaceutical formulations: the analysis of xanthine derivatives.

Micellar electrokinetic chromatography (MEKC) has been applied to the analysis of three different drugs. Although belonging to different therapeutic classes, all these drugs contain xanthine derivatives as active substances. Pentoxifylline was separated from eight related xanthines. Quantitative MEKC was applied to determine impurities (caffeine and xanthine) in the purified drug at the 0.05-0.1% level and also for the determination of the active substance in Agapurin tablets. Ethofylline and theophylline were separated from ephedrine and mebrophenhydramine and determined in Xantedrylettae tablets while caffeine was separated from mephenhydramine and determined in Kinedryl tablets. In all cases, simple borate buffers with sodium dodecyl sulfate as the surfactant were satisfactory and little separation optimization was required. The relative standard deviation (RSD) of the migration times was better than 1% while the RSD of the observed areas was better than 2%. This demonstrates that MEKC is a valuable alternative for the traditional high-performance liquid chromatography analysis of drugs and drug formulations.

On the possibility of performing chiral wall-coated open-tubular electrochromatography in 50 micron internal diameter capillaries.

Recent results have demonstrated acceptable enantiomer separations in open, 50 microns internal diameter capillaries, coated with a chiral stationary phase, a technique known as electrochromatography. According to existing literature, smaller column diameters, 10 microns or less, are generally preferred for this mode of operation. The conditions under which the wider columns can be used are discussed.

Quantitation of organic acids in sugar refinery juices with capillary zone electrophoresis and indirect UV detection.

During sugar refinement, monitoring of organic acids such as formate, tartrate, succinate, malate, glycolate and acetate in the process "juices" is important for process control. Matrix effects can lead to problems in conventional chromatographic ion analysis of these solutions. Capillary zone electrophoresis, with indirect UV detection, has been shown to be a good alternative, requiring almost no sample preparation, other than dilution, and with fast analysis time (less than 7 min). A co-elution problem for the formate-tartrate pair could be solved by adding small amounts of bivalent metal ions to the electrophoresis buffer. Quantitative analyses of the organic acids in the juices from beet sugar production and from the processing of a hydrolysed chicory root extract (Cichorium intybus) are reported.