Proficiency Testing of the XRF Method for Measuring 10 Major Elements in Different Rock Types

The X-ray Fluorescence Spectrometry (XRF) method was adapted for the determination of 10 major elements, such as silicon, aluminum, calcium and magnesium, in different types of rocks. The calibration curves were determined from 28 different types of rock standards which were fused into glass beads. The matrix effect was calibrated by using empirical factors. This method was used for determining the 10 major elements of samples from GeoPT proficiency testing. The 23 types of rock samples were analyzed over 15 years and the results indicate that this method is most effective in determining SiO₂, Al₂O₃, K₂O and CaO with the obtained|Z| < 2 for all samples. This method is also suitable for determining MgO, MnO, TiO₂ and Na₂O although each element has only one suspect result in different samples with the obtained|Z|>2, which was caused by the matrix difference between samples and standard samples in measuring the lower content elements. When the content of TFe₂O₃ is higher than 1.00% and P₂O₅ between 0.08% and 0.80%, the results can match expectations (the obtained|Z| < 2). To sum up, the developed XRF method has long term stability and is effective, which can match the expectation of applied geochemistry laboratories for determination of 10 major elements in different types of rock samples.