Preparation of Certified Reference Materials of Sillimanite for Chemical Composition Analysis

With an increasing utilization of sillimanite, some reference materials of sillimanite for chemical composition have been developed in countries such as the UK, South Africa and Japan. In China, there is only one national secondary standard material for chemical compositon of sillimanite. It is difficult to meet the research needs of the country in terms of the concentration gradient range and the value index. For this study, two sillimanite ores were collected from Linkou county in Heilongjiang and Leijiang county in Henan, and one sillimanite concentrate was collected from Linkou county in Heilongjiang. According to national primary reference materials specifications, 3 sillimanite CRMs have been developed and approved as national standard reference materials (GBW07843, GBW07844, GBW07845). For the homogeneity test, the calculated F values in 3 sillimanite CRMs obtained by analysis of variance (ANOVA) were less than the critical F values at the 95% confidence level, with the exception of TFe₂O₃ and Cu in Y-1, and MnO in J-1, indicating no obvious differences between units and within units. The differences of TFe₂O₃ and Cu in Y-1 and MnO in J-1 between units and within units resulted from the error in the analytical methods. The results showed that 3 sillimanite CRMs had good homogeneity. The calculated test statistic b₁ of 3 sillimanite CRMs during the 14-month observation period was statistically insignificant, indicating that 3 sillimanite CRMs were stable. 10 qualified laboratories were selected to give certified values and uncertainties of 39 components, including major elements, trace elements and sillimanite phases in ores. The relative expanded uncertainties of 39 components range from 0.60% to 29.9%. The content of Al₂O₃ in sillimanite reference materials is 25.85%, 28.16%, 55.06% for GBW07843, GBW07844, and GBW07845, respectively. 3 sillimanite CRMs meet the monitoring requirements of chemical composition analysis for sillimanite samples in geology and environment fields.