ADVANCED POSSIBILITIES ON MULTIELEMENT SEPARATION AND DETECTION OF METAL-IONS BY CAPILLARY ZONE ELECTROPHORESIS USING PRECAPILLARY COMPLEXATION .1. SEPARATION ASPECTS

Many metal ions can be separated by capillary zone electrophoresis (CE ) using cyclohexane-1,2-diaminetetraacetic acid (CDTA) as a complexing reagent for precapillary derivatization of analytes. Adding an organi c solvent, such as ethylene glycol, permits a wide selection in separa tion resolution. The effect of this electrolyte additive, as well as t hat of tetraalkylammonium salts, anionic and cationic surfactants, var ying berate buffer concentration and some operational variables (appli ed voltage, sample volume, etc.), was studied in detail with regard to electrophoretic and electroosmotic mobility. The gain in resolution i s due to the enhancing effect of electrolyte changes on the migration range and peak efficiency. An impact of modest electrophoretic velocit y changes is believed to occur in a much lesser degree. Under optimize d conditions, excellent separations of 23 metal-CDTA complexes within 10 min were obtained. Aluminium(III), antimony(III), bismuth(III), chr omium(III), mercury(II), palladium(II), silver(I), tallium(I), tin(IV) , uranium(VI), vanadium(IV,V) and zirconium(IV), which are scarcely su bject to conventional CE procedures, were separated, along with severa l other metal ions, using a 20 mM sodium berate buffer (pH 9.0) contai ning 5% ethylene glycol and 1 mM CDTA. The problem of improving the de tectability for complexed metal ions was also addressed.