Advanced possibilities on multi-element 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 organic solvent, such as ethylene glycol, permits a wide selection in separation resolution. The effect of this electrolyte additive, as well as that of tetraalkylammonium salts, anionic and cationic surfactants, varying berate buffer concentration and some operational variables (applied voltage, sample volume, etc.), was studied in detail with regard to electrophoretic and electroosmotic mobility. The gain in resolution is due to the enhancing effect of electrolyte changes on the migration range and peak efficiency. An impact of modest electrophoretic velocity changes is believed to occur in a much lesser degree. Under optimized conditions, excellent separations of 23 metal-CDTA complexes within 10 min were obtained. Aluminium(III), antimony(III), bismuth(III), chromium(III), mercury(II), palladium(II), silver(I), tallium(I), tin(IV), uranium(VI), vanadium(IV,V) and zirconium(IV), which are scarcely subject to conventional CE procedures, were separated, along with several other metal ions, using a 20 mM sodium berate buffer (pH 9.0) containing 5% ethylene glycol and 1 mM CDTA. The problem of improving the detectability for complexed metal ions was also addressed.