Determination of copper, zinc, cadmium and lead in a fish otolith certified reference material by isotope dilution inductively coupled plasma mass spectrometry using off-line solvent extraction

Copper, Zn, Cd and Pb concentrations in a fish otolith (ear stone) certifie d reference material (CRM) were determined by isotope dilution inductively coupled plasma mass spectrometry (ID-ICP-MS). The material consists of almo st pure calcium carbonate, and contained 39% calcium and less than 1 ppm of these heavy metals. An off-line solvent extraction was employed to separat e the metals from the sample matrix. Contamination from reagents and from t he extraction procedure was minimal and precise results were obtained for t hese four metals. The mean concentration (mg kg(-1) dry wt) and standard de viation (1 sigma) were 0.742 +/- 0.007 for Cu, 0.471 +/- 0.002 for Zn, 0.00 28 +/- 0.0002 for Cd and 0.0234 +/- 0.0003 for Pb (n=5). An ICP-MS determin ation by external calibration after solvent extraction was used as a back-u p method and the results obtained (Cu, 0.73; Zn, 0.43; Cd, 0.0028; Pb, 0.02 6; n=3 for each) were in good agreement with the ID-ICP-MS results. The pre sent ID-ICP-MS results are used as reference values of the fish otolith CRM .