DETERMINATION OF MG CU, ZN, AG AND PB IN PURE IRON BY ISOTOPE-DILUTION ANALYSIS INDUCTIVELY COUPLED PLASMA MASS-SPECTROMETRY

Isotope dilution analysis (ID) with inductively coupled plasma mass spectrometry (ICP-MS) was applied to the determination of ultra trace levels of impurities, such as Mg Cu, Zn, Ag and Pb in pure irons. Furthermore, a cation exchange method was combined with the ID as a pretreatment procedure in order to remove the iron matrix cation to preconcentrate impurities. It was found that the cation exchange method was very suitable for a pretreatment procedure for ID, because the cation exchange resin contained almost no contaminant elements after properly rinseing. Recoveries of elements by the cation exchange method were 50 to 86% for the above elements, and it was high enough to be combined with ID. Using ID-ICPMS, it was possible to measure 0.1 mug/g levels of these elements with R.S.D. of less than 4%. In particular, 1ng/g of Ag was determined with R.S.D. of less than 17%.