Assay of acetylsalicylic acid and three of its metabolites in human plasmaand urine using non-aqueous capillary electrophoresis with reversed electroosmotic flow

The separation of acetylsalicylic acid and three of its metabolites-salicyl ic acid, salicyluric acid and gentisic acid-is demonstrated in a non-aqueou s capillary electrophoresis system with reversed electroosmotic flow. Solve nt mixtures of methanol and acetonitrile are used for the electrophoresis m edia and different electrolytes have been investigated, The flow is reverse d by the addition of the polycation hexadimethrine bromide and thus a negat ive voltage is used. This system provides a fast and effective separation o f the four analytes. The separation method was applied to the assay of acet ylsalicylic acid and its major metabolites in plasma and urine and the limi ts of quantification for all of these compounds are about 5 mu g ml(-1) in plasma and 25 mu g ml(-1) in urine. (C) 1998 Elsevier Science B.V. All righ ts reserved.