Determination of trace amounts of Si in iron and steel using gel chromatographic separation followed by isotopic dilution ICP-MS

An analytical method was investigated to improve the sensitivity of trace amounts of Si in high-purity iron and steels. Silicon in steel was converted to [SiMo12O40](4-) and adsorbed on a dextran gel column. After elution with aqueous ammonia, Mo was determined by isotopic dilution/ICP-MS, which resulted in the determination of Si. The determination of Si by the present method was not interfered by the presence of Al, As, Co, Cr, Cu, Mn, Ni and Ti. The presence of P increased the apparent analytical Value of Si, which could be avoided by washing the gel column with 10 w/v% oxalic acid + 10 v/v% nitric acid solution prior to the elution of molybdosilicate. The limit of the determination was 0.05 ppm.