Determination of major and trace elements in alloy steels by nanosecond and femtosecond laser ablation ICP-MS with non-matrix-matched calibration

Abstract

Accurate elemental analysis of alloy steels is a prerequisite for providing high-quality product assurance. This study investigates the quantification capabilities of three laser systems: 257-nm femtosecond (300 fs), 213-nm Nd:YAG (3 ns), and 193-nm ArF* excimer (15 ns) lasers coupled with inductively coupled plasma mass spectrometry for the determination of major and trace elements in alloy steels. The results demonstrate that under typical operating conditions, the signal intensity of the 257-nm femtosecond (fs) laser system is approximately 10 and 3.6 times higher in comparison to the 193-nm ArF excimer and 213-nm Nd:YAG nanosecond (ns) lasers, respectively. The transient signals of the fs-laser also demonstrate greater stability compared to the ns-laser. In addition, significant differences in melting and elemental fractionation were observed among the three laser-ablation (LA) systems, with the highest observed for the 193-nm ns-LA. In contrast, calculated Fe-normalized elemental fractionation indices are close to 1 for most elements, and no significant melting was observed when employing the 257-nm fs-LA. In this work, internal standardization using 57Fe and 100% normalization-calibration strategy were employed in combination with NIST 610 (silicate glass) as a non-matrix-matched external calibration material. The concentrations of the major and trace elements found in alloy-steel samples illustrate that a significant improvement in the analytical results was obtained with fs-LA using non-matrix-matched calibration.