DETERMINATION OF TRACE-METAL IONS BY CAPILLARY-ELECTROPHORESIS WITH FLUORESCENCE DETECTION BASED ON POSTCOLUMN COMPLEXATION WITH 8-HYDROXYQUINOLINE-5-SULFONIC ACID

A method has been developed for the determination of aluminium and oth er metal ions (Ca, Mg, Zn, Cd) in aqueous samples. The metal ions are separated as the free cations by capillary electrophoresis. A solution of 8-hydroxyquinoline-5-sulphonic acid (HQS) is added post column to mix with the separation buffer. The resulting HQS complexes could be d etected by their fluorescence. The influence of the pH of the separati on buffer and the post-column reagent has been studied. For Al and Zn low-pH values were required, while far Ca and Mg a pH of 8-9 for the r eagent was optimal. The fluorescence intensities could be increased ap proximately three-fold by adding 20% (v/v) dimethylformamide to the re agent. Under optimised conditions detection limits in the low mu g l(- 1) level (approx. 0.l mu mol l(-1)) were obtained. The repeatability o f the peak areas was from 1.4% at high concentration to 8.4% at a conc entration of 0.25 mu mol l(-1). The speciation of aluminium ions in th e presence of fluoride was studied. (C) 1998 Elsevier Science B.V. All rights reserved.