Enantioseparation of erythro-mefloquine and its analogues in capillary electrophoresis

Elucidation of the Enantiodiscrimination Properties of a Nonracemic Chiral Alignment Medium through Gel-based Capillary Electrochromatography: Separation of the Mefloquine Stereoisomers

Enantiodiscrimination and enantioseparation are two highly important processes in chemistry, often performed by using NMR spectroscopy and chromatography. For a better understanding of the mechanistic details, the same system should be studied by both methods. In addition, isotropic and anisotropic NMR parameters should be obtained, the latter using alignment media so that residual dipolar couplings and chemical-shift anisotropies can be measured. Consequently, a chiral alignment medium was used for the first time in chiral gel-based capillary electrochromatography with the four stereoisomers of the antimalaria drug mefloquine as test compounds. Chromatographic data verify that enantiodiscrimination obtained with this alignment gel is caused by differences in the equilibrium constants related to associate formation. Hence, the chromatographic separation provides physicochemical data that form a basis for the understanding and optimization of alignment processes, and vice versa.

Capillary electrophoresis for pharmaceutical analysis

This chapter describes the application of capillary electrophoresis (CE) to pharmaceutical analysis. The areas of pharmaceutical analysis covered are enantiomer separation, analysis of small molecules such as amino acids or drug counter-ions, pharmaceutical assay, related substances determinations, and physiochemical measurements such as log P and pKa of compounds. The different electrophoretic modes available and their advantages for pharmaceutical analysis are described. Recent applications of CE for each subject area are tabulated with electrolyte details. Information on electrolyte choice and method optimization to obtain optimal separations is included.

Liquid-phase microextraction combined with high-performance liquid chromatography for the enantioselective analysis of mefloquine in plasma samples

A simple and rapid method, which involves liquid-phase microextraction (LPME) followed by HPLC analysis using Chiralpak AD column and UV detection, was developed for the enantioselective determination of mefloquine in plasma samples. Several factors that influence the efficiency of three-phase LPME were investigated and optimized. Under the optimal extraction conditions, the mean recoveries were 33.2 and 35.0% for (-)-(SR-)-mefloquine and (+)-(RS)-mefloquine, respectively. The method was linear over 50-1500 ng/ml range. Within-day and between-day assay precision and accuracy were below 15% for both enantiomers at concentrations of 150, 600 and 1200 ng/ml. Furthermore, no racemization or degradation were seen with the method described.

Evaluation of newly synthesized derivative of cyclodextrin for the capillary electrophoretic separation

A highly water-soluble new cyclodextrin (CD) derivative 2-O-acetonyl-2-O-hydroxypropyl-beta-CD (2-AHP-beta-CD) was synthesized and tested as an effective chiral selector for the capillary zone electrophoretic resolution (Rs) of several basic and acidic analytes. The primary purpose of the research was to explore the capability of the 2-AHP-beta-CD as chiral selectors on comparison with the neutral CDs such as beta-CD, DM-beta-CD and HP-beta-CD. Substitution with 2-O-acetonyl-2-O-hydroxypropyl group at the secondary hydroxyl sites of the CD is aimed at influencing the magnitude and selectivity of analyte-CD interactions. The chiral resolution was strongly influenced by the concentration of the CDs and buffer pH. 2-AHP-beta-CD showed the best enantiomer resolution properties among the tested compounds, while the other CDs showed inferior or no performances at all.