PRECONCENTRATION OF TRACE-METALS IN SEA-WATER MATRIX FOR DIFFERENTIAL-PULSE ANODIC-STRIPPING VOLTAMMETRY

A preconcentration procedure with two-step extraction was proposed to be used in conjunction with differential pulse anodic stripping voltam metry (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 Hg2+ solution at pH 3.5, as previously reported. The aqueous solutio n containing simply the enriched metals and the nonreacted Hg2+ was an alysed by DPASV using a glassy carbon electrode. Anodic stripping volt ammetry of the metals including Zn, Cd, Pb and Cu was conducted in the preconcentrated solution after adding 0.025 M KCl. The preconcentrate d solution was observed not to cause any interference in the anodic st ripping voltammetry. Besides, the Hg2+ could be in situ utilized as th e source of the mercury film coated on the glassy carbon electrode, re ndering it as an efficacious working electrode. The detection limits a chieved were as low as 0.004 mu g/l for Zn, 0.002 mu g/l for Cd, 0.002 mu g/l for Pb and 0.003 mu g/l for Cu in sea water by DPASV coupled w ith the preconcentration procedure with an enrichment factor of 20. Th e analytical reliability was confirmed by checking with NASS3 (NR-A4) open ocean sea water.