SELECTIVE ONLINE PRECONCENTRATION OF PROTEINS BY TANDEM METAL CHELATE-CAPILLARIES CAPILLARY-ZONE ELECTROPHORESIS

Fused-silica capillaries having surface bound iminodiacetic acid metal chelating functions were developed for the selective on-line preconcentration of dilute protein samples prior to capillary zone electrophoresis. The metal chelate capillaries with immobilized zinc proved effective in the selective accumulation of detectable amounts of proteins from dilute samples. They permitted the detection of 25 times less concentrated samples than by CZE alone with concentration sensitive detectors. Large sample volumes could be introduced without affecting separation efficiency. Besides demonstrating the effectiveness of metal chelate capillaries in the quantitative determination of proteins from dilute samples, the effects of pH, composition of electrolytes and sample feeding time on the analytical signal were examined with carbonic anhydrase, a zinc binding protein.