建立了王水水浴消解-原子荧光光谱法测定土壤和沉积物中砷、 汞、 硒、 锑和铋。 将试样置于50 mL具塞玻璃比色管中, 加入10 mL王水(1+1), 于沸水浴中消解2 h, 取出冷却后, 超纯水定容, 摇匀后取上清液待测。 相比于微波消解的昂贵设备和低安全(高温高压)性, 水浴消解法具有设备简单、 易操作、 重复性高等优点; 同时由于实际样品中汞、 硒和铋的含量都比较低, 水浴消解后的试样能直接上机测定, 可以大大地简化操作过程。 重点研究了硼氢化钾浓度对检测灵敏度的影响, 结果表明, 相同仪器条件下, 对于砷、 硒、 锑和铋元素, 高的硼氢化钾浓度能在一定程度上提高其荧光强度; 而对于汞而言, 低的硼氢化钾浓度反而能增加其荧光强度, 当采用0.1%硼氢化钾作为还原剂时, 汞可以获得较好的检测灵敏度。 通过比较不同预还原剂对测定结果的影响, 验证了该方法测定样品中硒的可靠性, 数据表明, 该方法消解所用的盐酸量足够将Se(Ⅵ)还原成Se(Ⅳ), 不仅不需要额外添加盐酸或硫脲, 向样品中添加硫脲反而会使测定结果偏低很多。 仪器最佳条件下, 采用王水水浴消解-原子荧光光谱法测定土壤或沉积物中砷、 汞、 硒、 锑和铋的方法检出限分别为0.008, 0.002, 0.002, 0.005和0.003 mg·kg-1(取样量为0.500 0 g, 定容体积为50 mL), 测定下限分别为0.032, 0.008, 0.008, 0.020和0.012 mg·kg-1。 该方法用于测定土壤/沉积物标准样品中砷、 汞、 硒、 锑和铋的相对误差范围分别为-3.3%~4.5%, -3.9%~15%, -20%~-7.8%, -13%~3.4%和2.2%~7.0%; 该方法用于测定实际样品, 相对标准偏差范围为1.3%~11%。 采用水浴消解原子荧光光谱法测定土壤和沉积物中砷、 汞、 硒、 锑和铋, 具有操作简便、 无需转移容器、 普及性强、 检出限低、 精密度和准确度好等优点, 分析结果满足环境监测要求。

A method for determination of the contents of As, Hg, Se, Sb and Bi in soils and sediments by atomic fluorescence spectrophotometry (AFS) was established by using aqua regia as the dissolved medium. The sample placed in a 50 mL glass colorimetric tube was dissolved with 10 mL aqua regia (1+1), then put the colorimetric tube in a boiling water bath and heated it 2 h, and then removed the colorimetric tube to cool, and then fixed with ultra-pure water and shaken to be tested. Compared with the expensive equipment and the low safety (high temperature and high pressure) of microwave digestion, the water bath digestion method has the advantages of simple equipment, easy operation and high repeatability. Considering that the content of mercury, selenium and bismuth in actual samples is relatively low, the sample after water bath digestion can directly be tested did not pretreat with any more acid or other reagent. The reducing agent (KBH4) is another factor that affects sensitivity. Under the same instrumentation conditions, experiments have shown that the fluorescence intensity for As, Se, Sb and Bi increased first and then decreased as the concentration of KBH4 increased, while the fluorescence intensity for Hg increases as the concentration of KBH4 decreases. In this study, when the concentration of KBH4 is 0.1%, it can get good sensitivity to detect Hg. In order to verify the reliability of the method, the effects of different pre-reducing agents to detect Se in soil and sediments were compared. The data showed that the amount of hydrochloric acid used in the digestion was sufficient to reduce Se(Ⅵ) to Se(Ⅳ), and it is not necessary to add hydrochloric acid or thiourea, but it makes the results much lower when the thiourea added into the sample. Under the optimal experimental conditions, the detection limit (LOD) found were 0.008 mg·kg-1 (for As), 0.002 mg·kg-1 (for Hg and Se), 0.005 mg·kg-1 (for Sb) and 0.003 mg·kg-1 (for Bi) (sample quantity 0.500 0 g, sample volume 50 mL), and the limit of quantitation (LOQ) found were 0.032 mg·kg-1 (for As), 0.008 mg·kg-1 (for Hg and Se), 0.020 mg·kg-1 (for Sb) and 0.012 mg·kg-1 (for Bi). The relative error ranges for the determination of As, Hg, Se, Sb and Bi in soil/sediment standard samples were -3.3%~4.5%, -3.9%~15.4%, -20.2%~7.8%, -13.0%~3.4% and 2.2%~7.0%, respectively. The relative standard deviation range for the determination of actual samples was 0.4%~10.3%. The method has the advantages of simplicity of operation, no need for transfer of containers, high accessibility, low detection limits, high precision and accuracy. The method also can satisfy the analysis requirement of environmental monitoring.