Simultaneous Determination of Thallium, Copper, Cadmium and Lead in Seawater by Isotope Dilution-Surfac e

Abstract

Isotope dilution-surface ionization mass spectrometry, contin uing to attract the attention of scientists because of its inherent theoretical and technical accuracy in environmental analyses, was applied to the determination of ppt (1012) level concentrations of thallium, copper, cadmium and lead in seawater samples using a quadri-spike solution of 203Tl, 65Cu, 116Cdand206Pb. The accuracy of the proposed method is exellent in comparison with other methods. Furthermore, the method is applied to the determination of the partitioning of their concentrations between particulates and liquid phase in sea water. Samples were taken from the surface of the Western Pacific Ocean, 2 km off Muroran-shi, Hokkaido. They were partitioned between both phases by ( 1 ) filtration through a Nucleopore filter, ( 2 ) centrifuging (10000 rpm, one hour) and or ( 3 ) ultrafiltration. Their concentrations in the sample are found to be 12.8±0.1ppt for thallium, 293± 6 ppt for copper, 46.0±0.3 ppt for cadmium and 70±1 ppt for lead, while these are partitioned between particulates and liquid phase as follows, in above unit, : Nucleopore-filtration (thallium: O.14 and 12, copper 25 and 260, cadmium: 1.21 and 45.3, lead: 39 and 31), Centrifugation (thallium: 0.32 and 12.4, copper: 71 and 227, cadmium: I.74and 45.4, lead: 52 and 19), ultrafiltration (bulk of thallium and cadmium being partitioned in particulates of molecular weight smaller than 103 and/or liquid phase, while others being veiled due to contaminations from the ultrafiltration device). These figures, however, showed distinct changes reflecting a variability of coastal environments.