Chiral separations of 1,3,4-thia- and 1,3,4-selenadiazine derivatives by use of non-aqueous capillary electrophoresis

Our aim was to establish suitable conditions for the chiral separation of 12 1,3,4-thia- and 1,3,4-selenadiazine derivatives; some of them were identified in screening tests as potential antituberculotics. To overcome possible problems with the water insolubility of most analytes, we profited by the advantages of non-aqueous capillary electrophoresis. Methanol, formamide, and a mixture of formamide with acetonitrile (1:2, v/v) were used as separation media. Hydroxyethyl-, hydroxypropyl-, and methyl-beta-cyclodextrin were applied as chiral selectors in concentrations of 200 mM. Besides the effect of these different electrophoretic media and selectors, we also investigated the consequences of using different electrolytes (25 mM ammonium acetate/1 M acetic acid and 25 mM citric acid/12.5 mM TRIS). Distinct differences of the separation factors in the different separation media were observed. Depending on structure characteristics of the analytes, we established clear classifications to these cyclodextrins (CD), which were most appropriate for the separation of the enantiomers of the particular analytes.