METHODS FOR CONCENTRATING METAL-IONS PRIOR TO ANALYSIS BY ION CHROMATOGRAPHY OR CAPILLARY ELECTROPHORESIS

In ion chromatography and particularly in capillary electrophoresis, i t is often necessary to preconcentrate metal ions to be determined and to remove larger amounts of matrix ions such as Na+, Mg2+, and Ca2+. Several general techniques for concentration of selected metal ions ar e reviewed and illustrated by specific examples. These techniques incl ude the use of chelating resins and the formation of soluble complexes in solution with subsequent retention by ordinary solid-phase extract ion (SPE) columns. Many of the chelating resins used in the past for p reconcentration of metal cations have been relatively inefficient. Mor e effective resins can be created by careful attention to the particle size and physical structure of the resin, its chelating capacity, and the selectivity and kinetics of the chelating groups present in the r esin. Likewise, carefully designed soluble complexing reagents can be used effectively in conjunction with modem SPE techniques. These princ iples are illustrated by new types of chelating resins and reagents th at we have prepared and tested.