Spark ablation inductively coupled plasma mass spectrometry analysis of minor and trace elements in low and high alloy steels using single calibration curves

Abstract

A unidirectional high current pulse spark with a very fast rise-time, ensuring a rapid and complete transfer of energy to the sample, was used as the sampling system for the analysis of carbon steels and highly alloyed steels with the same operating conditions. The sparking operating conditions were optimised and a restrictive path was designed to decrease the quantity of eroded material reaching the plasma, in order to prevent deposition of material in the torch injector, and to minimise sampling cone blockage and drift effects. Spark ablation sampling efficiency and effectiveness of the restrictive path were evaluated. To compensate for differences in the amount of material ablated or for a variation in drift, ⁵⁷ Fe and ⁵⁵ Mn were used as internal standards. The calibration procedure was applied to the analysis of the elements Al, B, Co, Cu, Mn, Nb, P, Si, and V, present in the following certified reference materials: BCS (Bureau of Analysed Samples) SS-456 to SS-460 (residual series); CRMs (European Committee for Iron and Steel Standardisation) No 285-2 (Maraging steel), No 292-1 (niobium stabilised steel), No 295-1 (highly alloyed steel), and No 296-1 (jethete steel). When plotting intensity ratios (I _X /I _IS ) versus concentration ratios (C _X /C _IS ) linear calibration curves over the entire range of tested concentrations, with correlation coefficients better than 0.999, were obtained. Determination limits below 1 µg g ^–1 were found and the precision was better than 2.8%. It has also been shown to determine carbon contents at concentration levels greater than 0.03% with RSD values below 3%. For the elements As, Sn, Ti, W and Zr, only present in one or two of the Standard Materials, the sensitivity was also evaluated. Furthermore, the possibility of obtaining reproducible transient signals from sparking periods of only a few seconds was demonstrated.