OPTIMIZATION OF THE INDIRECT FLUOROMETRIC DETECTION FOR THE SIMULTANEOUS ANALYSIS OF INORGANIC ANIONS AND POLYCHARGED ORGANIC-ANIONS BY CAPILLARY ELECTROPHORESIS

Until now, fluorescein sodium salt has been used to generate the backg round signal for indirect fluorimetric detection of inorganic cations or mono-charged organic anions separated by Capillary Zone Electrophor esis (CZE). In this paper, we extend the use of fluorescein sodium sal t to the simultaneous CZE analysis of inorganic anions (Cl-, NO2-, NO3 -, SO42-, F-) and poly-charged organic anions (oxalate and citrate). T he electroosmotic flow was reversed by using tetradecyltrimethylammoni um bromide (TTAB) or hexadimethrine. The specific problems linked to t he simultaneous utilization of fluorescein sodium salt and a positivel y charged capillary were studied and resolved by reducing the fluoresc ein/TTAB interactions and by optimizing the fluorophore concentration in the electrolyte. The study of reproducibility and the quantitative approach led to very good results. In such conditions the quantificati on of Cl-, NO3- and SO42-, in different mineral and spring waters, has been successfully realized. In addition, the detection thresholds rea ched the range of one hundred to a few hundred ppb.