Determination of trace element abundances in GSJ reference rock samples using lithium metaborate-lithium tetraborate fused solutions and inductively coupled plasma mass spectrometry

This study aims to establish a quantitative method for determination of trace element abundances in rock samples using LiBO_2-Li_2B_4O_7 fused solutions and inductively coupled plasma mass spectrometry (ICP-MS). Alkali fusion of rock powders has an advantage in assuring complete dissolution of refractory minerals, but the analyte solution diluted from the alkali-fused glass is known to cause matrix effects during ICP-MS analysis. The present study adopted the following procedures: (1) The alkali fusion of the rock powders was made using a rock:flux ratio of 1:2. (2) The alkali fused glass samples were digested using 5% HNO_3-0.1% HF to yield solutions with high dilution factors of 6000-8000 times. (3) The internal standard method was adopted to construct the calibration curves. Concentrations of the internal standard element (10 ppb In) were kept constant in the solutions of both the reference and unknown samples. The results show that abundances of Sc, V, Cr, Co, Ni, Rb, Sr, Y, Zr, Nb, Cs, Ba, 14 REEs, Hf, Ta, Pb, Th, and U were successfully determined in representative standards from the Geological Survey of Japan (JA-1, JA-2, JA-3, JB-1b, JB-2, JB-3, JG-1a, JG-2, JG-3, JGb-1, JR-1, JR-2, and JR-3).