Decomposition of marine sediments for quantitative recovery of chromium and inductively coupled plasma mass spectrometric analysis

A method is described for the determination of total chromium in National Research Council of Canada Certified Reference Material (CRM) sediments HISS-1, PACS-2 and BCSS-1 using inductively coupled plasma mass spectrometry (ICP-MS). Complete solubilization of Cr was achieved with closed vessel microwave digestion using a mixture of HNO 3 and HF followed by an open beaker reflux with HClO 4 and H 2 SO 4 for 8-12 h at 290 °C. Subsequent quantification by quadrupole ICP-MS required complete removal of residual HClO 4 and H 2 SO 4 in order to eliminate polyatomic ion interferences on 52 Cr and 53 Cr from 35 ClOH, 34 S 18 O and 37 ClO, respectively; this was achieved by baking the residue at 335 °C. Values of 30.0±3.4, 95.6±1.0 and 123±2 μg g –1 were obtained for HISS-1, PACS-2 and BCSS-1, respectively, in agreement with their respective certified values of 30.0±6.8, 91.8±5.8 and 123±14 μg g –1 . The detection limit (3σ), based on a 0.25 g sample and a 250 ml final volume, was 0.4 μg g –1 . The methodology is suitable for the determination of other trace elements of interest in these sediments.