Determination of cobalt, copper, mercury, and nickel as bis(2-hydroxyethyl)dithiocarbamate complexes by high-performance liquid chromatography

Ammonium bis(2-hydroxyethyl)dithiocarbamate (HEDC) is used as a precolumn derivatizing reagent for the reversed-phase HPLC determination of Co(II), Cu(II), Hg(II), and Ni(II). The metal-HEDC complexes are soluble in water, which eliminates the need to extract them into an organic solvent prior to analysis. Co(II), Cu(II), and Ni(II) can be determined by direct aqueous injection onto a C18 column in the range of 0.005-10.0 mg/L, with a precision of 1.5-3.2%. Detection is at 405 nm. The Hg(II)-HEDC complex is preconcentrated on an on-line adsorption column prior to HPLC analysis. After preconcentration, Hg(II) can be determined in the range of 0.02-25..mu..g/L with a precision of less than 2%. The analysis of spiked electroplating waste waters showed good agreement with expected values.