| Summary: | BACKGROUND Three acids and four acids dissolution methods are the two main dissolution methods for determination of rare earth, cobalt, hafnium, indium, manganese, niobium, tantalum, thallium, chromium, cadmium, gallium, germanium, vanadium and tin in geological samples by inductively coupled plasma-mass spectrometry (ICP-MS). However, the composition of geological samples is complex, the content of rare earth and other metal elements is low, and the properties of each element are different, which makes the measurement results of volatile elements such as vanadium, chromium, cadmium, gallium and tin unstable, and rare earth elements such as lanthanum, cerium, praseodymium and neodymium are not completely dissolved by three acids or four acids. OBJECTIVES To improve the four acids dissolution system for the determination of 28 elements including rare earth elements and rare metal elements. METHODS The method of HCl-HNO3-HF-HClO4-H2SO4 was developed by addition of H2SO4 in the dissolution system of HCl-HNO3-HF-HClO4. A new analysis method has been developed for the certified reference material of stream sediment, soil and rock, and 28 elements including rare earth elements in samples were determined simultaneously by ICP-MS with 10ng/mL 103Rh and 185Re as the internal standard by on-line injections. RESULTS The accuracy of volatile elements such as vanadium, chromium, cadmium, gallium and tin was improved by 1.4%-14.6%, and that of rare earth elements such as lanthanum and cerium was improved by 0.2%-8.9%. The certified reference materials of stream sediment (GBW07301a), soil (GBW07408) and rock (GBW07107) were analyzed to test the method. The determined values were in good agreement with the certified values. The standard deviations (RSD) of the method were 1.14%-9.84% and accuracy (△lgC) was not higher than 0.1. CONCLUSIONS This method is rapid, simple, and accurate and can meet the requirements for determining the content of rare earth, cobalt, hafnium, indium, manganese, niobium, tantalum and other metal elements in large quantities of geological samples.
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