Determination of structurally related phenothiazines by capillary zone electrophoresis and micellar electrokinetic chromatography

Fourteen structurally related basic phenothiazines were determined by capillary zone electrophoresis (CZE) and micellar electrokinetic chromatography (MEKC), applying electrolyte systems containing the fluorinated cationic surfactant FC 135. Effective mobilities of the phenothiazines were determined as a function of pH by CZE in the anionic mode with a reversed electroosmotic flow (EOF). Larger differences in overall effective mobilities were obtained in MEKC, applying the cationic surfactant cetyltrimethylammonium bromide as micelle forming agent. The quantitative abilities and matrix effects of CZE with reversed EOF were studied, and as an example the concentrations of thioridazine and promethazine in pharmaceutical preparations were determined.