Development and application of an analyte/matrix separation procedure for multi-element trace analysis of steel alloys by means of sector-field ICP-mass spectrometry

Abstract

An analytical procedure, based on the use of sector-field ICP-mass spectrometry (ICP-SFMS), was developed for the determination of Be, B, Al, P, S, Ti, Ge, As, Se, Zr, Nb, Rh, Pd, Sn, Sb, Hf, Ta, W, Re, Ir and Pt in a high-alloy steel matrix, consisting mainly of Cr, Fe and Ni, in addition to lower amounts of Si, V, Mn, Co, Cu and Mo. To reduce the impact of spectral and non-spectral interferences, an analyte/matrix separation procedure based on cation-exchange chromatography was developed and applied. In the chromatographic protocol used, most of the first row transition metals are retained on AG 50Wx8 resin, whereby ca. 97.5% of the initial matrix can be separated from the rapidly eluting target elements. The main matrix constituents accompanying the rapidly eluting target elements are Si, Mo and ca. 5% of the total Cr, the latter of which unavoidably elutes prematurely. The finalised procedure was applied to CRMs and real high-alloy steel samples (T91, 316L and 15–15Ti). The experimentally determined concentrations for the CRMs were found to be in good agreement with certified values. Analysis of the real samples revealed the presence of measureable amounts of most of the target elements in at least one of the three steels, with the exception of Be, S, Se, Hf and Ir. For elements not natively found in the CRMs or the real samples under study, recoveries of 100% (within reproducibility uncertainty) were obtained when analysing mock samples. Procedural limits of quantification (10s LoQs) were determined by subjecting blanks to the entire procedure. These were found to range from low ng g⁻¹ levels for Re to sub-mg g⁻¹ levels for S.