Determination of trace and ultra-trace elements in saline waters by inductively coupled plasma mass spectrometry after off-line chromatographic separation and preconcentration

Abstract

A method for the determination of trace and ultra-trace elements in sea-water by ICP-MS, after preconcentration and matrix removal using a commercially available ion-chelation system, was developed and optimized. Cellulose-immobilized ethylenediaminetriacetic acid was used as the column material and elution profiles were determined with an on-line configuration. Recovery experiments were carried out, firstly in a simple matrix (spiked de-ionized water) and secondly in a complex matrix (synthetic sea-water) employing a preconcentration factor of either 10 or 100. In both types of matrix, recoveries of between 90 and 110% were obtained for Cd, Co, Cu, Ni, Pb, U, Y and the 14 REEs. Excess recoveries were obtained for Zn and are thought to result from reagent contamination. Reproducibility was in the range 0.20–7.25% coefficient of variation. Optimized conditions were used to analyse National Research Council of Canada CRMs, Estuarine Water SLEW-1, Open Ocean Sea-water NASS-4 and Nearshore Sea-water CASS-2. Accuracy and precision are related to concentration. Cd, Co, Cu and Ni show good accuracy for concentrations greater than 1 ng ml^–1. Both short term instrumental precision and between sample reproducibility are typically better than 10% RSD. Although the rare earth elements are not certified in any of the reference materials, a relatively smooth sea-water normalized plot is seen for SLEW-1.