UTILIZATION OF FLUORESCEIN SODIUM-SALT IN LASER-INDUCED INDIRECT FLUOROMETRIC DETECTION .2. APPLICATION TO ORGANIC-ANIONS

Previously, we have used the fluorescein sodium salt to generate the b ackground signal in the indirect fluorimetric detection of inorganic c ations (alkaline; alkaline earth metals and transition metals) separat ed by capillary zone electrophoresis (CZE). In this work, we report th at the use of fluorescein sodium salt can be extended to the detection of organic anions. A study of the detection thresholds and of reprodu cibility (elution times and effective electrophoretic mobilities) was performed. As samples we used, on the one hand, a mixture of n-alkane sulfonates (from C-1 to C-10) and, on the other hand, a mixture of car boxylic acids (from C-1 to C-18). Under the optimal conditions, detect ion thresholds of about 700 to 800 ppb were obtained and the reproduci bility of effective electrophoretic mobilities was characterized by a relative standard deviation of about 0.5%. Calibration curves were als o established (correlation coefficients were found to be between 0.995 and 0.9998). Finally, we compared the evolution of the experimental r esponse coefficients of these two series of samples as a function of a lkyl chain length with theoretical response coefficients obtained from findings reported by Ackermans et al. [J. Chromatogr., 549 (1991) 345 ].