Simultaneous determination of multiple trace element compositions in thin (<30 μm) layers of BCR-2G by 193 nm ArF excimer laser ablation-ICP-MS: implications for matrix effect and elemental fractionation on quantitative analysis

Abstract

The latest generation of quadrupole ICP-MS instruments coupled with a 193 nm ArF excimer laser system (LA-ICP-MS) allows quantitative analysis for ultra-trace elements (ppm ~ ppb) from the small amount of solid materials. Multiple trace element compositions (Li, Be, B, Sc, V, Cr, Mn, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Nb, Mo, Cs, Ba, REE, Hf, Ta, Tl, Pb, Th and U) were simultaneously determined from thin layer (<30 μm) BCR-2G basalt glass reference materials using LA-ICP-MS. The effects of differences in matrix compositions (matrix effect) and elemental fractionation on the calibration technique for quantitative analysis, which involves combinations of external reference materials and internal standardization, were examined by using NIST SRM 612 (soda-lime glass) and two different elements (⁴²Ca and ²⁹Si) as an external reference material and internal standard elements, respectively. The elemental fractionation was found for several elements (B, Si, V, Mn, Ni, Zn, Rb, Mo and Pb). The effects of elemental fractionation on quantitative analysis are, however, practically negligible when the compositions were determined from thin layer samples, i.e., low depth-to-diameter ratio of laser pit, when ablating >50 μm pit diameter. No apparent differences between the Ca-normalized measured values and the Si-normalized one were found for both BCR-2G and natural minerals (clinopyroxene and amphibole in mafic rock). The measured values of BCR-2G are in agreement (within 20%) with the previous values for most elements (within 10% for REE except for Tb), except for Zn, Ga and Pb, in spite of large differences in matrix compositions between external reference material (NIST SRM 612) and the unknown sample (BCR-2G).