Accurate determination of elements in silicate glass by nanosecond and femtosecond laser ablation ICP-MS at high spatial resolution

Despite the large number of successful applications of LA-ICP-MS, elemental fractionation remains the main limitation for many of its applications in the Earth sciences. This limitation is particularly notable for high spatial resolution analysis. Elemental fractionation and mass-load effect in silicate glasses NIST SRM 610 and GSE-1G were investigated by using 193 nm ArF excimer nanosecond (ns) laser and 257 nm femtosecond (fs) laser ablation systems coupled to inductively coupled plasma mass spectrometry. Contrary to those observed in ns-LA-ICP-MS, the most elemental fractionation at the small spot sizes of 16-24 mu m are lower than that at the large spot sizes of 44-60 mu m in fs-LA-ICP-MS. The significantly different fractionation behaviors of Li, Na, Si, K, V, Cr, Mn, Fe, Co, Ni, Cu, Rb, Cs and U between silicate glass materials NIST SRM 610 and GSE-1G observed in 193 nm excimer LA-ICP-MS are eliminated by using 257 nm fs-LA-ICP-MS at high spatial resolution. In addition, the mass load effect and matrix dependent mass load effect are also found to be reduced by using fs-LA-ICP-MS in comparison with ns-LA-ICP-MS. Except for Sb, Pb and Bi, the elemental fractionation is independent on the laser fluence chosen, which is irrespective of ns- or fs-LA-ICP-MS. In this study, a spot size of 24 mu m was used to test the capabilities of LA-ICP-MS analysis at high spatial resolution. The agreement between our data and the reference values is better than 10% for most of the elements in MPI-DING, USGS, and NIST glasses by using fs-LA-ICP-MS. For ns laser ablation analysis, the accuracy is highly dependent on the calibration strategies used (conventional external calibration method or 100% oxide normalization method) and the selected external reference materials (NIST SRM 610 or GSE-1G). The much less laser-induced elemental fractionation and matrix effect in fs-LAICP-MS in comparison with 193 nm excimer LA-ICP-MS make it more suitable for the analysis of silicate materials at high spatial resolution. (C) 2015 Elsevier B.V. All rights reserved.