Preconcentration of trace metals in sea water matrix for differential pulse anodic stripping voltammetry

Abstract

A preconcentration procedure with two-step extraction was proposed to be used in conjunction with differential pulse anodic stripping voltammetry (DPASV) for the determination of trace metals in sea water. The two-step extraction involved extraction of trace metals from sea water with dithiocarbamate into chloroform followed by backextraction with a Hg 2+ solution at pH 3.5, as previously reported. The aqueous solution containing simply the enriched metals and the nonreacted Hg 2+ was analysed by DPASV using a glassy carbon electrode. Anodic stripping voltammetry of the metals including Zn, Cd, Pb and Cu was conducted in the preconcentrated solution after adding 0.025 M KCl. The preconcentrated solution was observed not to cause any interference in the anodic stripping voltammetry. Besides, the Hg 2+ could be in situ utilized as the source of the mercury film coated on the glassy carbon electrode, rendering it as an efficacious working electrode. The detection limits achieved were as low as 0.004 μg/1 for Zn, 0.002 μg/1 for Cd, 0.002 μg/1 for Pb and 0.003 μg/1 for Cu in sea water by DPASV coupled with the preconcentration procedure with an enrichment factor of 20. The analytical reliability was confirmed by checking with NASS-3 (NR-A4) open ocean sea water.