Preparation of Certified Reference Materials of Diatomite for Chemical Composition Analysis

Diatomite is an important mineral resource, widely used in traditional industries such as food, medicine, chemical industry, and construction, as well as emerging industries such as new generation information technology, new energy, and high-end equipment manufacturing. At present, there is only one reference material for the composition of diatomite abroad, with few fixed value components and exhausted use. There is no reference materials for diatomite composition analysis in China. The SiO₂ content is a key indicator for evaluating the quality of diatomaceous earth, but it cannot distinguish whether it comes from diatomite or associated silicate minerals. To meet the needs of exploration and comprehensive utilization of diatomite resources, candidate samples were collected from major diatomite producing areas and typical mining areas in China, such as Changbai County in Jilin Province, Tengchong City in Yunnan Province, and Shengzhou City in Zhejiang Province. Three types of diatomite composition analysis reference materials (GBW07742-GBW07744) have been developed. The homogeneity test and stability test of 33 components, including diatom content (amorphous SiO₂), SiO₂, Al₂O₃, TFe₂O₃ were carried out using inductively coupled plasma-optical emission spectroscopy (ICP-OES) and inductively coupled plasma-mass spectrometry (ICP-MS). Ten laboratories were selected to jointly determine the reference materials using a combination of classical chemical methods and instrumental analysis methods. The results showed that the measured F values of the three reference materials were all below the F critical value, with good uniformity. The short-term and long-term stability test results showed no directional changes and statistically significant differences. According to JJF1006-1994 and JJF 1343—2012, certified values and uncertainties have been established for 33 components. This series of reference materials has achieved the determination of amorphous SiO₂ (diatom content) in diatomite for the first time, solving the problem of being unable to distinguish whether SiO₂ comes from diatoms or associated silicate minerals. The diatom content, SiO₂, Al₂O₃, TF₂O₃ and other components have a good gradient, which can cover high, medium and low-grade diatomaceous earth products. The number of certified elements and their concentration ranges are superior to those of existing similar international reference materials, which can meet the needs of diatomite resource exploration, development, and comprehensive utilization.