Use of Xenon as Internal Standard for the Accurate Determination of Trace Elements in Water Samples by ICP-MS

Application of xenon (Xe-129) as an internal standard for the precise and accurate determination of several trace elements in different kinds of water samples by inductively coupled plasma mass spectrometry (ICP-MS) is described. The novelty of this approach is that no external addition of any reagent is involved since xenon is present as an impurity in the plasma gas itself. As a result, the possibility of introducing any type of elemental impurities through the addition of an internal standard will be completely avoided. Therefore, this feature will be of great value when determinations are carried out for elements present at ng/mL and sub-ng/mL levels. The utility of Xe-129 as an internal standard has been validated using standard reference materials NIST 1640d, NIST 1643e, and NIST 1640a. The accuracies and precisions achieved were markedly better when internal standardization was applied. In general, trace element data in a variety of water samples were obtained with < 5% RSD with comparable accuracy in each case, suggesting that this method can be applied routinely for the determination of trace elements in water.