BACKGROUNDFrom 1986 to 2007, different grades of trace gold certified reference materials (background grade, anomaly grade, medium grade and high grade) and mineral gold certified reference materials (mineralization grade, cutoff grade and concentrate grade) had been developed by IGGE and used for regional geochemical survey, mineral exploration and evaluation, mining and smelting. With the increase of the service life period and the consumption of recent years, most of the gold certified reference materials has been used up or almost used up. New gold standard materials need to be developed urgently.

OBJECTIVESTo develop a new gold certified reference material and compare it with the original gold certified reference material.

METHODSThe trace gold certified reference materials in 7 levels and mineral gold certified reference materials in 3 levels were prepared in strict accordance with relevant specifications. The collected candidates were sampled from different types of deposits and different matrices. The collected candidates were prepared through coarse crushing, drying, composite configuration, fine crushing, sieving, blending and other steps. After the particle size inspection, the cumulative content of the sample with a particle size of 0.74μm reached more than 99%, which met the requirements of the specifications. 25 bottle samples of each grade were randomly selected. Homogeneity testing was carried out by ICP-MS, FAAS and GFAAS.

RESULTSThe relative standard deviation (RSD) was less than 10%, and the F values of the variance test were less than the one-tailed critical value F_{0.05(24, 25)} of 1.98, indicating that the sample uniformity was good. During the one-year investigation period, no significant changes in statistical significance were found in the fixed value components, which proved that the stability of the sample was good. Five highly experienced and skilled laboratories in geology gold samples testing in CHN were invited to evaluate the gold certified reference materials by classically reliable analytical methods. The original data conformed to the normal distribution after statistical inspection and the suspicious values were eliminated. The arithmetic mean was used as the standard value, and the uncertainty was evaluated in detail, in accordance with the latest specifications. The certified value of the copied standard material was accurate and reliable, and the uncertainty was reasonable. It was approved as a national first-level standard material in 2019. Compared with the original batch, the certified values of the two batches were basically the same, and the standard deviation of the fixed value data showed a shrinking trend, which met the requirements for copying standard materials.

CONCLUSIONSThis series of gold standard materials has a wide content range, and meets the value comparison and analysis monitoring of different content levels. Moreover, it has good applicability, and meets the needs of geological and mineral research, regional geochemical investigation, gold mine exploration and evaluation.