Separation of dithiocarbamate metal complexes by micellar electrokinetic chromatography

Abstract

Separation of a number of transition metal complexes with bis(2-hydroxyethyl)dithiocarbamate (HEDTC) by micellar electrokinetic capillary chromatography (MEKC) with direct photometric detection was investigated. Pre-capillary complexation was shown to be superior to on-capillary complexation in terms of the number of metals ions which could be detected and their peak shapes, enabling analysis of Cd(II), Pb(II), Pt(II), Co(II), Ni(II), Bi(III), Cr(II), Cu(II) and Hg(II). The type and composition of the background electrolyte (BGE) were investigated with respect to separation selectivity and BGE stability. A BGE of 60 mM 3-(morpholino)propane sulfonic acid (MOPS), 30 mM tris(hydroxymethyl)aminomethane (Tris), 10 mM sodium dodecyl sulphate (SDS) and 100 µM HEDTC, pH 7.2 was found to be optimal with nine metals baseline separated in less than seven minutes, and giving separation efficiencies of up to 367000 theoretical plates, reproducibility of corrected peak areas below 3% relative standard deviation, concentration detection limits from 0.04 to 1.3 µM and mass detection limits at sub femtomole levels (detection at 254 nm).