High Pressure Sealed Digestion-Determination of 50 Elements in Geochemical Samples by Inductively Coupled Plasma Mass Spectrometry

ICP-MS was applied to the determination of 50 elements in geochemical sample. The sample (0.100 0 g) was digested with 3 mL of HF and 1 mL of HNO₃ in the PTFE-liner of the pressurized hermetically-sealed digestion system at 150℃ for 2 h. After cooling and de-pressurizing, the liner was taken out and 0.25 mL of HClO₄ was added to the digested solution, and the mixed solution was evaporated by heating at 150℃ until ending of the acid-fuming. 1 mL each of HNO₃ and H₂O was added, and the liner was replaced into the steel case of the digestor and the mixture in the liner was digested once more at 150℃ for 12 h. After natural cooling, the solution in the liner was transferred to a 10 mL PTFE colorimetric tube, and its volume was made up to 10.0 mL with water. A aliquot of 1.0 mL was taken from this mother sample solution and transferred to another 10 mL PTFE colorimetric tube and its volume was diluted to 10.0 mL with φ 2.2% HNO₃ solution to keep the concentration of HNO₃ at ca. φ 3%. This solution was used for MS determination of 28 elements (including Li, Be, V and etc. as shown in S1) and of 16 elements (including Sc, Y, La and etc. as shown in S2). Another aliquot of 1.0 mL was taken from the mother solution and placed into another 10 mL PTFE colorimetric tube, 2 drops of φ 10% HF solution and 1 mL of 500 g·L^-1 tartaric acid solution were added, and its volume was diluted to 10.0 mL with ca. φ 2.5% HNO₃ solution. This solution was used for determination of the remaindering 6 elements (including Ti, Zr, Nb and etc. as shown in S3). Eleven equations were established for calibration of errors of determined values of the respective 11 elements due to MS interferences. The proposed method was applied to the analysis of 6 CRMs of GBW 07359, GBW 07360, GBW 07361, GBW 07408, GBW 07427 and GBW 07446 in which the related 50 elements was determined giving results in consistency with the certified values, and meeting with the requirements for testing quality given in the management standard for geological laboratories.