Determining Cadmium in Marine Sediments by Inductively Coupled Plasma Mass Spectrometry: Attacking the Problems or the Problems With the Attack?†

Abstract

The importance of interelement interference of one trace element on another is highlighted in the determination of low levels of Cd in marine sediments by ICP-MS, both during an interlaboratory proficiency test and in the analysis of certified reference materials. Initial values obtained for the CRMs MESS-1 and BCSS-1 after an HF-based digestion were up to 50% higher than the certificate values, although the ratio of the Cd isotopes at m/z 111 and 114 agreed with that for the natural abundance of Cd. Investigations revealed that a polyatomic interference on ¹¹¹Cd, arising from the relatively large concentrations of Zr in the digests, was very similar in size to the isobaric interference of ¹¹⁴Sn on ¹¹⁴Cd in these materials. Appropriate corrections derived from the analysis of single element interferent solutions gave concentrations indistinguishable from the certificate value, with detection limits of 0.043 and 0.060 mg kg^–1 for ¹¹¹Cd and ¹¹⁴Cd, respectively. The study highlights the problem of obtaining consistent datasets between laboratories using different sample preparation schemes for environmentally important trace elements close to the detection limit.