Determination of trace and rare earth elements in marine sediment reference materials by ICP-MS : Comparison of open and closed acid digestion methods

Abstract

The ICP-MS determination of REE and several other trace elements in six USGS and Canadian marine sediment reference materials (GSMS-2, GSMS-3, HISS-1, PACS-2, MESS-1, MESS-3) was investigated. The sediment samples were dissolved following open and closed acid digestion procedures, and the methods were evaluated and compared. About 50 mg of the sample powder was used in both digestion techniques with an appropriate dilution, making the solutions suitable for ICP-MS analysis. 103 Rh was used as an internal standard to compensate for the signal drift due to changes in the nebulizer efficiency and other associated matrix interferences. Excellent agreement was observed between the ICP-MS data obtained by both digestion techniques and the certified values, (where available for comparison), for the majority of elements, including all REEs. For a few of the trace elements, such as Cr, Ni, Sr, and Pb, the closed digestion method was found to be very effective due to the controlled temperature and pressure maintained on the sample for many hours. The accuracy and precision achieved was better than 5% RSD in most cases, and the detection limits for most of the elements were in the ppt to sub-ppt range. For the first time, this study provides comprehensive data of trace and REEs by ICP-MS in GSMS-2, GSMS-3, HISS-1, PACS-2, and MESS-3 for which currently only few trace and very few REE-certified values are available in the literature. The analytical data of five marine sediment samples collected from the Bay of Bengal showed that the closed acid digestion technique is a suitable method for the precise ICP-MS determination of trace elements and REEs.