石墨消解-原子荧光光谱法测定土壤中汞、砷、硒和锑的含量

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

取土壤样品0.25 g,以10 mL体积比3∶1∶4的盐酸-硝酸-水混合液为消解液,于120℃石墨消解3 h,每30 min摇晃1次,冷却后,用水定容至25 mL。以2 g·L^(-1)氢氧化钾-0.2 g·L^(-1)硼氢化钾混合液为汞的还原剂,5 g·L^(-1)氢氧化钾-20 g·L^(-1)硼氢化钾混合液为硒、砷、锑的还原剂,以5%(体积分数)盐酸溶液为载流,采用原子荧光光谱法测定其中汞、砷、硒和锑的含量。结果表明,汞、砷、硒和锑的质量浓度在一定范围内与对应的原子荧光强度呈线性关系,检出限(3.143s)分别为0.0005,0.008,0.002,0.007 mg·kg^(-1),低于HJ 680-2013中的检出限。分析不同类型的土壤标准样品,测定值均在认定值的不确定度范围内,测定值的相对标准偏差(n=6)均小于15%。按标准加入法进行回收试验,回收率为94.0%~103%。

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 0.0005,0.008,0.002,0.007 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%.