Determination of 8 Precious Metal Elements in Single Minerals of Chalcopyrite by Inductively Coupled Plasma Mass Spectrometry with Alkali Melting and Resin Separation

Single mineral samples of chalcopyrite are often accompanied by precious metal elements such as gold and silver. When smelting copper, accompanying elements such as precious metal elements are also comprehensively recoveried. Therefore, accurate determination of each precious metal element in the sample is of great significance, but corresponding methods have not been reported. The method mentioned by the title was proposed by optimizing melting, resin separation conditions, and correcting coexisting element interference. An aliquot (0.200 0 g) of the sample was placed into a corundum crucible, and 0.5 g of sodium hydroxide was added. The temperature was raised to 700 ℃ from room temperature, and the mixture was melt for 5 min. Then 1.5 g of sodium peroxide was added while still hot, and the mixture was melt at 700 ℃ for 30 min. After cooling down, the mixture was added into the hot water and boiled at 200 ℃ for 3 min. The crucible was washed by water, the washing solution was collected and combined with the sample solution, and the acidity was adjusted to pH 1 by the solution of hydrochloric acid and nitric acid at volume ratio of 3∶1 (aqua regia). Then 1.0 g of mixed resin prepared by mixing A21 type anion exchange resin with R1S-82 polystyrene skeleton thiourea chelating resin at mass ratio of 2∶8 was added, and adsorption was conducted at 70 ℃ for 60 min. The resin was removed, and 20 mL of 10 g·L⁻¹ thiourea solution and 20 mL of 50% (volume fraction) aqua regia solution were added for desorption at 90 ℃ for 60 min. The desorption solution was diluted to 100 mL by 3% (volume fraction) nitric acid solution, and an aliquot (1 mL) was taken, and diluted to 10 mL by 3 mol·L⁻¹ nitric acid solution. The resulting solution was analyzed by inductively coupled plasma mass spectrometer. Internal standard lutetium was added online to compensate for matrix effects and sensitivity drift. The desorption solution contained trace amounts of copper, nickel, and lead, which interfered with the determination of rhodium and ruthenium with low content, and the corresponding interference could be corrected by formulas. It was shown that linear relationships between values of the mass concentration and the mass spectrum intensity of the 8 precious metal elements (platinum, palladium, rhodium, iridium, ruthenium, osmium, gold, and silver) were kept in definite ranges, with detection limits (3s) in the range of 0.04-0.17 ng·g⁻¹ for 7 elements (0.11 μg·g⁻¹ for silver). Investigation on precision and accuracy for single mineral samples of chalcopyrite was made, giving RSDs (n=6) of the determined values in the range of 0.47%-4.4%, and the spiked recoveries in the range of 97.2%-102%.