Determination of Mercury, Arsenic, Selenium and Antimony in Soil by Atomic Fluorescence Spectrometry with Graphite Digestion

The soil sample (0.25 g) was taken and digested by graphite digester at 120℃ for 3 h, shaking once every 30 min, using 10 mL of a mixture of hydrochloric acid, nitric acid and water at a volume ratio of 3:1:4 as the digestion solution. After cooling, the volume of the solution was made up to 25 mL with water. Mercury, arsenic, selenium and antimony in the above solution were determined by atomic fluorescence spectrometry with 2 g·L^-1 potassium hydroxide-0.2 g·L^-1 potassium borohydride mixture as the reducing agent of mercury, 5 g·L^-1 potassium hydroxide-20 g·L^-1 potassium borohydride mixture as the reducing agent of selenium, arsenic and antimony, and 5% (φ) hydrochloric acid solution as the carrier current. As shown by the results, linear relationships between values of atomic fluorescence intensity and mass concentration of mercury, arsenic, selenium and antimony were found in definite ranges, with detection limits (3.143s) of 0.000 5, 0.008, 0.002, 0.007 mg·kg^-1, respectively, which was less than the detection limits in HJ 680-2013. The method was applied to analysis of different types of soil standard samples, and the determined values were within the uncertainty ranges of the certified values, with RSDs (n=6) of the determined values less than 15%. Test for recovery was made by standard addition method, giving results in the range of 94.0%-103%.