On-line removal of Ca, Na and Mg from iminodiacetate resin for the determination of trace elements in seawater and fish otoliths by flow injection ICP-MS Original Research Article

A method is presented for the determination of trace elements in seawater and fish otoliths by inductively coupled plasma mass spectrometry (ICP-MS) with flow injection (FI) on-line separation and pre-concentration. Optimum separation and removal of Ca, Na and Mg from a typical seawater sample (NASS-5) was studied by variation of the sample loading time, loading pH, selective pH washing of the iminodiacetate-based resin and configuration of an extra valve in the FI system. These steps were necessary in order to minimize the interferents and permit calibration using the isotope dilution technique. The improved procedure was also validated by analysis of a certified seawater reference material CASS-3. A cod fish otolith, consisting of a calcium carbonate matrix was analyzed. Solution limits of detection (3s) were 3.0, 11, 12, 0.1, 1.0, 5.5 and 11 ng l−1 for Cu, Ni, Zn, Co, Pb, Cd and Fe, respectively, in the dissolved otolith sample. Precision was generally better than 3% R.S.D. (n=7) for all the elements at 1.0 μg l−1.