CHEMICAL MODIFICATION OF CAPILLARY COLUMN FOR ELECTROPHORETIC SEPARATIONS OF TRANSITION-METAL IONS

The surface modification of a fused-capillary for the separation of transition metal ions is described. A comparison was made of the properties of capillaries for each reaction stage, containing NH2, COOH and CONHOH functional groups, with those of the unreacted capillary by electroosmotic flow measurements and its dependence on pH. Multi-component mixtures of transition metal complexes with 4-(2-pyridylazo)resorcinol were separated in modified capillaries containing NH2 and COOH functional groups with an ammonia-ammonium buffer of pH 9.0 at an applied voltage of 15 kV followed by direct UV-Vis detection at 520 nm. Others were separated using the treated capillary containing CONHOH groups with pH 4.0 imidazole (5 mM)-alpha-hydroxyisobutyric acid (8 mM) as electrophoresis buffer, followed by indirect UV detection at 214 nm. The effects of electrophoretic buffer parameters on the complexation reaction and migration behaviour are discussed. Experimental results indicated that incorporating the chelating functional group in the inner wall of the capillary markedly enhances the selectivity of the system. Further, the optimum separation efficiencies were obtained by employing capillaries containing CONHOH functional groups.