Removal of the Iron Matrix by Cloud-Point Extraction with Ammonium Thiocyanate for the Analysis of Iron Metals

Abstract

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.