Determination of trace elements in unalloyed steels by flow injection inductively coupled plasma mass spectrometry

Abstract

A direct multi-element flow injection inductively coupled plasma mass spectrometry (FI-ICP-MS) method is described for the determination of trace elements in unalloyed steels. The applicability of FI-ICP-MS combined with microwave sample digestion for simultaneous analysis of trace amounts of Al, Ti, V, Cr, Co, Ni, Cu, As, Zr, Nb, Mo, Ta, W, Pb and Bi in unalloyed steels samples has been investigated. The advantage offered by FI-ICP-MS in comparison with conventional solution nebulization results in detection limits in the nanogram of analyte per gram of Fe range, because of the small dilution factor. Severe depression matrix effects caused by the Fe were encountered when the signal was compared with that from HNO₃ solutions. The FI and ICP operating parameters were optimized and suitable internal standards were added to correct for these matrix effects and for ion signal instability. Samples were analysed using a delivery rate of 2.8 ml min^–1, a nebulizer flow rate of 1.100 ml min^–1, a forward power of 1.5 kW and Be, Tl and Rh as internal standards, along with HNO₃ multielement standard calibration solutions (without Fe matrix matching). Results are given for two pure Fe reference materials (CRM 097 and NIST 365). The relative standard deviation for all analytes was <3% for concentrations above 1 µg g^–1.