Effect of electrolyte and solvent composition on capillary electrophoretic separation of some pharmaceuticals in non-aqueous media

Non-aqueous capillary electrophoresis was used to study the separation selectivity of positively charged drug substances and negatively charged diuretics. Study was made of the effects of organic solvent composition and the background electrolyte on the separation. The separation selectivity could be altered considerably by varying the methanol/acetonitrile composition. In addition, the migration order and the resolution of the pharmaceuticals could be altered merely by changing the electrolyte cation or the anion. The electrolytes tested were alkali metal acetates, ammonium acetate, ammonium chloride and ammonium bromide. As with aqueous background electrolyte solutions, the electroosmotic flow was decreased with increasing size of the alkali metal cation of the electrolyte in methanol/acetonitrile 50:50 (v/v). (C) 1999 Elsevier Science B.V. All rights reserved.