Determination of Mercury in Mixed Lead-Zinc Concentrates by Calcium Oxide Sulfur Fixation-Catalytic Pyrolysis-Gold Amalgamation Enrichment-Cold Vapor Atomic Absorption Spectrometry

After grinding, drying, and cooling, 0.100 0 g of the sample was taken, evenly spread on a sample boat, and mixed with approximately 0.05 g of calcium oxide. Then, the mixture was covered with another approximately 0.05 g of calcium oxide. The determination was conducted by cold vapor atomic absorption spectrometry at 800 ℃ for 180 s, with a detection wavelength of 253.7 nm. It was shown that the mercury masses exhibited nonlinear quadratic relationships with the corresponding absorbances in the ranges of 1–20 ng and 20–1 000 ng, respectively, and the detection limit was 0.63 ng. The proposed method was applied to the analysis of 8 mixed lead-zinc concentrate samples with different sulfur contents and varying phase compositions. RSDs （n=11） of the mercury determined values were all less than 5.0%, with recoveries ranging from 96.4% to 107%. The determined values were consistent with those obtained by the standard method YS/T 461.6—2013. The reproducibility limit （r） derived from 11 parallel tests conducted by 12 laboratories was r=0.057 5X+0.009, and the reproducibility limit （R） was R=0.082 1X+0.036 （where X was the determined mass fraction of mercury in the sample）.