SEPARATION OF XANTHINES AND URIC ACIDS BY CAPILLARY ZONE ELECTROPHORESIS AND MICELLAR ELECTROKINETIC CAPILLARY ELECTROPHORESIS

A CZE method was developed for the separation of xanthines and uric acid derivatives which are normally present in human plasma and urine as metabolites of caffeine. The methyl-substituted uric acids were separated using a 0.05 M sodium phosphate buffer (pH 7.0) at an applied voltage of 10 kV. In contrast, the separation of the methyl-substituted xanthines was only possible in the MECE mode, where SDS (0.15 M) was added to the buffer system. When both types of compounds were present in the same sample, optimum resolution (12 peaks for 13 standard solutes) was realized in the MECE mode with 0.15 M SDS added to the 0.05 M, pH 7 phosphate buffer at an applied voltage of 15 kV.