Speciation-capable field instrument for the measurement of arsenite and arsenate in water.
Speciation-capable field instrument for the measurement of arsenite and arsenate in water.
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DOI：
10.1021/ac050193e
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发表时间：
2005-08
影响因子：
7.4
通讯作者：
K. Toda;Takashi Ohba;Mariko Takaki;S. Karthikeyan;S. Hirata;P. Dasgupta
中科院分区：
文献类型：
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作者：
K. Toda;Takashi Ohba;Mariko Takaki;S. Karthikeyan;S. Hirata;P. Dasgupta
氢化物发生形成胂，并将胂在线预富集到碱性 KMnO4 接收器中，然后对形成的砷酸盐进行钼蓝 (MB) 比色测定，用于对总无机 As 和 As(III) 进行高灵敏度和单独测量。通过NaBH4将As还原为AsH3；当pH为1时，所有无机As都被还原为AsH3；当pH为7时，仅As(III)被还原。通过电磁泵不断添加 NaBH4，在两个不同的胂发生器中同时进行两种不同 pH 水平的还原。 AsH3 由填充有 KMnO4 固定溶液的各个多孔膜扩散洗涤器收集，两个洗涤器的内容物依次进入流量分析流。 MB 是通过与钼酸铵-抗坏血酸试剂混合、通过加热的反应器而形成的，然后由基于 LED/光电二极管的吸光度检测器进行测量。使用三种经过认证的天然水样确认了总砷的稳健性。通过该方法分析的井水样品的形态分析数据与不同实验室的 HPLC-ICPMS 测量结果非常吻合。该系统已成功应用于 As(III) 和 As(V) 的现场测量，其含量明显低于 1 微克/升。对于 20 mL 样品，这种廉价仪器的 As(III) 和总 As 的检测限 (LOD) 均为 0.3 microg/L。分析 80 mL 样品时，LOD 为 0.07 microg/L As(III) 和 0.09 microg/L 总 As。一般方法应该适用于许多其他感兴趣的分析物种类，这些分析物种类可以通过形成可以重新捕获的合适的挥发性化合物而从基质中分离出来。
Hydride generation to form arsine and in-line preconcentration of the arsine into an alkaline KMnO4 receiver followed by molybdenum blue (MB) colorimetric determination of the arsenate formed is proposed for the highly sensitive and separate measurement of total inorganic As and As(III). Reduction of As to AsH3 is carried out by NaBH4; when the reduction is carried out at pH 1, all the inorganic As is reduced to AsH3, and when carried out at pH 7, only As(III) is reduced. Reductions at the two different pH levels are carried out in two different arsine generators simultaneously using constant addition of NaBH4 with solenoid pumps. The AsH3 is collected by individual porous membrane diffusion scrubbers filled with a stationary solution of KMnO4, and the contents of the two scrubbers sequentially enter a flow analysis stream. MB is formed by merging with a ammonium molybdate-ascorbic acid reagent, passing through a heated reactor, and is then measured by a LED/photodiode-based absorbance detector. Robustness was confirmed for total As using three types of certified natural water samples. Speciation analysis data from well water samples analyzed by this method agree well with HPLC-ICPMS measurements in a different laboratory. The system has been successfully applied to field measurements of As(III) and As(V), where levels were significantly below 1 mug/L. For a 20-mL sample, the limits of detection (LODs) for this inexpensive instrument are 0.3 microg/L for both As(III) and total As. When an 80-mL sample is analyzed, LODs are 0.07 microg/L As(III) and 0.09 microg/L total As. The general approach should be applicable to many other analyte species of interest that can be isolated from the matrix by the formation of a suitable volatile compound that can be recaptured.