1. Institute of Geophysical and Geochemical Exploration, Chinese Academy of Geological Sciences, Langfang 065000, China
2. China University of Geosciences，Beijing 100083, China
3. Central Laboratory of North China Geological Exploration Bureau, Sanhe 065201, China
4. TJ-Standard (Tianjin) Metrology Testing Co., Ltd., Tianjin 300380, China
Abstract：Homogeneity is one of the three characteristics of reference materials. X-Ray Fluorescence Spectrometry has lots of strengths, like simplicity, high precision，and multiple elements simultaneous analysis. So X-Ray Fluorescence Spectrometry is one of the important methods to test the homogeneity of reference materials. At present, the application of X-Ray Fluorescence spectrometry to test the homogeneity of reference materials is still controversial. The homogeneity test requires that the sample weight is the minimum, and the general geochemical reference materials minimum sample weight is 0.1 g. The sample weight is about 4 g when the XRF is used for the homogeneity test; the obtained result is theoretically insufficient to support whether the sample is homogeneous under the condition of the minimum sampling weight. Based on the optimization of instrument parameters，this study changed the size of the previous pelleting mold to make the sampling weight 0.1 g, using pressed powder pellets, selected three soil (GBW07425, GBW07428, GBW07388) and three stream sediment (GBW07375, GBW07378, GBW07379) certified reference materials, each reference material taken from 15 bottles, sampling 2 from each bottle, the number of the total samples is 30, choosing SiO2, Al2O3, Fe2O3, MgO, CaO, Na2O, K2O, Mn, Ti and P 10 components to test. According to the single factor analysis of variance of F values and measured values of the standard deviation (S) and the relative standard deviation (RSD) comprehensive to evaluate the homogeneity of reference materials. Through theoretical calculation showed that the minimum sample weight of 10 main components was less than 0.1 g under the condition that the radiation radius of the sample was 5 mm. The results with 0.1 g pressed powder pellets showed that the accuracy of the method in this study was high, the relative errors were less than 16%, the precision was high, the relative standard deviations were no more than 4.3%, the F values were less than the critical values, and the homogeneity of soil and sediment certified reference materials was good. X-Ray Fluorescence Spectrometry is applied for determination under the condition that the minimum sampling amount is 0.1 g, which can not only solve the long-standing dispute in the homogeneity test of geological reference materials but also provide technical support for the application of X-Ray Fluorescence Spectrometry in other fields.
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