OBJECTIVESIon-adsorption type rare earth ore is extremely important in China and rare in the world. It is China's dominant mineral resource. At present, all the rare earth elements in the existing REE reference materials are oxide minerals, not ion-adsorption type, and cannot be exchanged with strong electrolytes. These reference materials cannot be used to monitor the leaching process of ion-adsorption type REE.

METHODSThe samples were collected from the typical ion-adsorption type REE weathering crust in Jiangxi Province. After being dried and ball-milled to 200 mesh, they were mixed for 1.5h. The contents of rare earth elements in the ionic phase were analyzed to test the homogeneity by ammonium sulfate leaching and inductively coupled plasma-mass spectrometry (ICP-MS).

RESULTSResults showed that the F values for the variance test were less than the threshold, which indicated a good homogeneity. The stability of monitoring samples was tested 4 times in two years, and no statistically significant changes were observed, indicating good stability of the samples. An accurate and reliable leaching analytical method was used in 8 technologically significant laboratories to finalize the contents of ionic phase rare earth elements. The determined values of nine monitoring samples were given by statistical calculation, including weighted average value and total uncertainty results which were from uncertainties in certified values, between-bottle homogeneity and long-term stability. These nine monitoring samples have certified values of 15 ionic phase rare earth elements except Sc.

CONCLUSIONSThe reference materials can be used to monitor the leaching process and provide metrological support for the analysis of rare earth elements in ionic phase during the evaluation and effective utilization of REE mineral resources.