The present paper describes a facile method for the determination of trace impurities in iron metals. This method is based on the selective removal of the matrix element as hydroxide precipitate followed by the determination of desired trace elements left in the solution. To an iron sample solution were added ethylene glycol bis(2-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) and diethylenetriamine. The iron(III) matrix was almost completely (>99%) precipitated at pH 9.5, while trace elements [Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Pb(II)] were left in the solution due to the complexation with EGTA and diethylenetriamine. The sufficient removal of the matrix element and negligible loss of trace elements allowed the sensitive determination at ng g -1 levels by inductively coupled plasma-mass spectrometry.KEY WORDS: matrix precipitation; iron(III) hydroxide; trace metals; high-purity iron; inductively coupled plasma-mass spectrometry.
Synopsis :To an iron sample solution were added ammonium thiocyanate, ethylenediaminetetraacetic acid, and polyoxyethylene-4-nonylphenoxy ether (nonionic surfactant, average number of ethylene oxides 7.5). The nonionic surfactant was segregated from the solution by heating at 80°C. The thiocyanato complex of iron(III) was nearly completely collected in the surfactant phase, leaving trace elements [e.g., Mn(II), Ni(II), and Bi(III)] in the aqueous phase. The trace elements were determined by graphite-furnace atomic absorption spectrometry. The proposed method was successfully applied to the analysis of high-purity iron.
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