Determination of cadmium in oyster tissue using isotope dilution inductively coupled plasma mass spectrometry:: comparison of results obtained in the standard and He/H2 cell modes

An inductively coupled plasma quadrupole mass spectrometer equipped with an octopole collision/reaction cell was used for the determination of cadmium in oyster tissue samples using isotope dilution inductively coupled plasma mass spectrometry. The oyster samples in question were found to contain Mo and Zr. In our feasibility study on a Cd standard solution (10 mu g L-1) containing a matrix of Mo (1000 mu g L-1) or Zr (250 mu g L-1), the potentially interfering species (MoO+ or ZrO+) present at the analytical mass of cadmium concerned (m/z 111, 112 or 114) was reduced effectively through the use of a mixture of He and H-2 as cell gases. The accuracy of the method was validated by the analysis of a matrix-matched certified reference material (CRM) of NIST SRM 1566b. The CRM was analyzed under the standard and He/H-2 cell modes. Two isotopic pairs of Cd-114/Cd-111 and Cd-112/Cd-111 were selected for quantification purposes. The recoveries of cadmium obtained in the two cell modes were compared with each other. The validated method was applied successfully to the APMP.QM-P5 pilot study for international comparability purposes.