Determination of cadmium in food samples by ID-ICP-MS with solid phase extraction for eliminating...

A solid phase extraction (SPE) method using chelating resin was developed to separate Cd from spectral-interferences prior to the analysis of food samples by isotope-dilution inductively coupled plasma mass-spectrometry (ID-ICP-MS). Two syringe-driven chelating columns (SDCCs), Nobias Chelate PB-1M and InertSep ME-1, were investigated in the present experiment. The results of the pH dependence of Mo removal rates showed that separation of Cd and Mo could be obtained at pH conditions over 7. In addition, 0.6 mL of NH(4)OH solution added into each 10 mL of digested sample solution (in 0.3M HNO(3)) followed by SPE was enough to remove the interfering elements, i.e. Mo, Zr, and Sn, in ID-ICP-MS analysis of Cd. Furthermore, it was found that InertSep ME-1 was more effective for separating Cd from the interfering elements, with removal rates approximately 100% for Mo, Zr, and Sn while the recovery of Cd was approximately 100%. The optimized SPE operations were as follows: 0.6 mL of NH(4)OH was added into each 10 mL of digested sample solution; the sample solution was loaded into each pre-cleaned SDCCs at a flow rate of 5 mL min(-1); after 5 mL of ultrapure water was passed through the SDCC for washing, 2 mL of 0.3M HNO(3) was passed through to elute Cd and the eluent was subjected to ICP-MS measurement. The present method was validated by analyzing five certified reference materials (CRMs) produced by the National Metrology Institute of Japan (NMIJ), and then was applied to a soybean powder sample.