Liquid chromatography of metal chelates. Chromatographic studies of homologous dialkyldithiocarbamates

Abstract

The chromatographic behaviour of a selected group of metal dithiocarbamates was investigated by reversed-phase, liquid chromatography. Ligands with the general formula R 2NCSSNa, where R is CH 3CH 2–, CH 3CH 2CH 2–, (CH 3) 2CH–, CH 3CH 2CH 2CH 2– or CH 3CH 2CH 2CH 2CH 2– were synthesised and used to prepare the corresponding complexes of zinc(II), arsenic(III), iron(III), cadmium(II), lead(II), nickel(II), copper(II), mercury(II), cobalt(III) and chromium(III). The chromatographic behaviour of the metal complexes on a C 18 column was examined with the mobile phases comprising methanol–water, acetonitrile–water and methanol–acetonitrile–water. With the exception of one ligand [where R=(CH 3) 2CH–], the majority of the chelates were resolved satisfactorily. Although the Cd(II) and Pb(II) complexes were not resolved by the binary solvent systems, those derived from the straight-chain, higher homologues (C 3–C 5) were successfully separated with ternary solvent mixtures. Chelates of Zn(II), Fe(III) and the diethyldithiocarbamate of As(III) were not observed using any of these mobile phases.