Exchange Reactions with Zinc Bis[(2-hydroxyethyl)dithiocarbamate] for Automated Monitoring of Metal Ions in Industrial Effluents by Liquid Chromatography with Electrochemical Detection

On-line mixing of industrial effluents with a buffered aqueous solution of the water-soluble zinc bis[(2-hydroxy ethyl)dithiocarbamate] complex (or mixtures of zinc nitrate and ammonium bis(2-hydroxyethyl)dithiocarbamate) leads to the automated formation of dithlocarbamate complexes of metals such as copper, cobalt, nickel, and cadmium. Automated injection of the complexes formed in this way into a slowly flowing (<0.8 mL min^-1) 40/60 methanol-water (buffer) solvent mixture followed by oxidative electrochemical detection at +0.9 V vs Ag/AgCl of the dithlocarbamate complexes separated on a C₁₈ chromatographic column completes the development of a highly efficient microprocessor-controlled system for trace metal determination in Industrial effluents. The high stability of the zinc complex, the absence of any electroactive ligand, the ability to use water-soluble complexes, and the requirement of only small amounts of nonaqueous solvent allow considerable improvements to be made in long-term (7 day) monitoring of metals in industrial effluents relative to existing approaches.