微波消解-氢化物发生原子荧光光谱法测定污泥中汞和砷

Determination of mercury and arsenic in sludge by microwave digestion-hydride generation atomic fluorescence spectrometry

利用高压密闭微波消解技术消解样品，建立了氧化物发生原子荧光光谱法测定污水处理厂污泥中汞和砷的方法。对消解酸和消解程序进行了优化，同时讨论了硼氢化钾浓度对测定的影响。结果表明，选用10mL硝酸-盐酸（4＋6）可将0．25g污泥样品消解完全；确定消解程序如下：消解功率为850W，发射率为80％，第1步采用5min内从室温升温至110℃，保持5min，第2步采用10min内继续升温至180℃，保持20min；在硼氢化钾浓度为20g／L时进行测定，效果最佳。汞和砷的方法检出限分别为0．0016mg／kg和0．0022mg／kg。方法应用于污泥样品中汞和砷的测定，相对标准偏差（RSD，n=6）分别为2．7％～3．8％和1．1％～2．0％，汞和砷的加标回收率分别为96％～102％和98％～104％。方法应用于土壤标准样品GSS-25和GSS-26中汞和砷的测定，结果与认定值一致，汞和砷的RSD（n=6）分别为4．5％～7．4％和2．2％～2．4％．

After the sample was digested with high-pressure sealed microwave digestion technology, a method for determination of mercury and arsenic in sludge from sewage treatment plants was estab- lished by hydride generation atomic fluorescence spectrometry. The digestion acid and the digestion procedure were optimized and the influence of potassium borohydride concentration on the determina- tion was discussed. The results showed that 0.25 g of the sludge samples could be completely digested with 10 mL of mixed acid of nitric acid and hydrochloric acid （4＋6）. The digestion procedure was de- termined as follows： digestion power of 850 W and the emissivity of 80℃, the temperature was raised within 5 min from room temperature to 110 ℃ and kept for 5 min for the first step, and the tempera- ture was further raised to 180 ℃ within 10 min and kept for 20 min for the second step. When the po- tassium borohydride concentration was 20 g/L, the result was optimum. The detection limits of this method for mercury and arsenic were 0. 001 6 mg/kg and 0. 002 2 mg/kg, respectively. The method was applied to the determination of mercury and arsenic in sludge samples, the relative standard devia- tions （RSD, n=6） were 2.7%-3.8 % and 1.1%-2.0%, respectively, and the recoveries for mercury and arsenic were 96%-102% and 98%-104%, respectively. When the method was applied to soil certi- fied reference materials GSS-25 and GSS-26, the results were consistent with the certified values and the RSDs（n=6） for mercury and arsenic were 4.5%-7.4 % and 2.2%-2.4 %, respectively.