Direct determination of trace metals in sea-water using electrothermal vaporization inductively coupled plasma mass spectrometry

Abstract

A method is described for the direct analysis of five transition elements (Co, Cu, Mn, Ni, V) in sea-water using ETV-ICP-MS. Interferences from the sea-water matrix were eliminated by a combination of in situ separation of analyte and matrix components in the ETV, and use of nitric acid as a chemical modifier. The nitric acid facilitates the removal of chloride from the sea-water matrix during the sample drying stage, whilst optimization of the ETV heating programme allows for effective separation of residual matrix and analyte species, thus reducing ionization suppression and space charge effects in the ICP-MS. Calibration standards, prepared by spiking a sea-water matrix stripped of trace metals by ion exchange, gave excellent linearity and allowed for direct determination of selected analytes without the use of standard additions. Detection limits ranged from 0.003 µg l–1 for V to 0.14 µg l–1 for Cu. The precision and accuracy of the method were checked by analysis of two certified reference sea-waters.