EFFECT OF ELECTROLYTE-COMPOSITION ON THE SEPARATION OF INORGANIC METAL-CATIONS BY CAPILLARY ION ELECTROPHORESIS

Capillary ion electrophoresis (CIE; Waters' tradename Capillary Ion Analysis) is a capillary electrophoresis technique in which the conditions for separation are optimized for the analysis of inorganic or low-molecular-weight ions. Among the variable parameters in CIE, control of the electrolyte composition provides one of the more significant means for manipulating separations. In the separation by CIE of mixtures of various alkali metal, alkaline earth metals and transition metals their relative selectivity could be changed by altering the pH and the concentration of the complexing agent in the electrolyte. To permit the use of indirect photometric detection and to ensure symmetrical peak shape a highly UV absorbing amine, with an electrophoretic mobility similar to those of the analyte cations, was chosen as the major component of the electrolyte. The reproducibility in terms of the migration times was less than 0.5% relative standard deviation and in terms of peak area was better than 2% relative standard deviation. Detection limits ranged from low to mid-parts per billion (10(9)). Applications of this technique for the analysis of metal cations in tap water. orange juice and in acid-etching baths is demonstrated.