Comparison of four ligands for the determination of cobalt in trace amounts by solvent extraction and graphite furnace atomic-absorption spectrophotometry

Abstract

Diethylammonium diethyldithiocarbamate (DDDC), ammonium tetramethylene dithiocarbamate (ammonium pyrrolidine dithiocarbamate; APDC), 1-nitrosonaphth-2-ol and 2-nitrosonaphth-1-ol were compared as ligands for the determination of trace amounts of cobalt by graphite furnace atomic-absorption spectrophotometry after extraction into xylene. The reproducibility of injecting the xylene phase was improved by coating the sampling capillary of the injection device with a carbon fluoride compound. Copper, iron, manganese and zinc at concentrations up to several thousand times that of cobalt interfered seriously when using DDDC and APDC as ligands. With the two nitrosonaphthols as ligands, only copper with 1-nitrosonaphth-2-ol interfered, making 2-nitrosonaphth-1-ol recommendable for the determination of trace amounts of cobalt. The detection limit is 1 ng ml^–1.