EVALUATION OF CARRIER ELECTROLYTES FOR CAPILLARY ZONE ELECTROPHORESIS OF LOW-MOLECULAR-MASS ANIONS WITH INDIRECT UV DETECTION

Indirect UV detection in capillary zone electrophoresis has been investigated with respect to transfer ratios for low-molecular-mass analyte anions and chromate or various aromatic carboxylic acids acting both as carrier electrolytes and detection probes. The transfer ratio can be regarded as a measure of the effectiveness by which analyte ions displace the UV-absorbing probe ions and has been found to depend on the relative mobilities of the analyte and the carrier. Highest values of transfer ratios have occurred when the carrier ion had a higher mobility than the analyte ion. This trend follows the Kohlrausch theory, but still considerable deviations between calculated and experimental data have been encountered. Consideration of the transfer ratio, the molar absorptivity of the probe and the degree of separation achieved, suggests that chromate is the best electrolyte for high-mobility inorganic anions. The results obtained enable predictions of the most suitable carrier electrolyte for various applications with indirect UV detection.