Preparation of standard composites for the trace element analysis by X-ray fluorescence

Abstract

Synthetic standards were prepared for the determination of 12 trace elements (Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Ba, Pb and Th) by X-ray fluorescence. Pure chemical reagents of elements of interest were mixed with major-element composites with similar chemical composition to the anorthite-diopside eutectic mixture. The mechanically mixed standards were melted in an electric heater at about 1400°C for the complete homogenization and subsequently quenched in distilled water. The quenched glasses were analyzed by an electron probe microanalyzer (EPMA). Except for CaO, the analytical values gave a good agreement with values calculated by weight of used chemical reagent within the error range of EPMA. The glasses were pulverized and mixed with standard rock samples issued by Geological Survey of Japan to make the variation of major-element composition wider. Synthesized standards range from 43.81 to 73.69% for SiO2 and from less than 10 to about 600 ppm for most trace elements. The fusion technique with the mixture of sample and flux (Li2B4O7) in the proportion of 1:2 was applied to the analysis. Precision of calibration curves, corrected for matrix effect by iron content, is high enough to analyze trace elements of concentration above 10 ppm in igneous and sedimentary silicate rocks.