We have examined matrix-masking method for analyzing iron and steels by ICP-OES with ion exchange separation. In the ion exchange separation of impurity elements from iron matrix, it is vital to separate only those elements that are targeted. Therefore, the matrix element was masked with ethylenediamine tetra-acetic acid (EDTA) to prevent the interference with the procedure of ion exchange separation of impurities. Specimen was decomposed by heating with nitric acid, and added 4.0 g of EDTA. Only impurities were adsorbed by cation-exchange resin, whereas iron combined with EDTA was not absorbed. The impurities adsorbed by resin were eluted by nitric acid, and those were measured by ICP-OES. This method enabled to separate matrix Fe by over 99.9%. We found, therefore, the recoveries of aluminum, calcium and magnesium were over 98%. The analytical result of manganese impurities of the Japanese iron and steel CRMs of a JSS003-4 and JSS168-7 were in good agreement with those of the certified values.
