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矿泉水中的总砷

AN-V-210

2020-10

zh

Straightforward determination by voltammetry on a gold microwire electrode

低浓度砷在地壳中无处不在。矿床和矿石中的砷含量较高。这些矿藏中的砷以亚砷酸盐（AsO33-）和砷酸盐（AsO43-）的形式渗入地下水，造成地下水污染。除了天然来源的砷，工业和农业也会造成较小程度的污染。世界卫生组织《饮用水水质准则》中的无机总砷指导值为“饮用水水质指南》将无机总砷的指导值定为 10 微克/升。 阳极剥离伏安法的检测限（LOD）为 0.9 微克/升，是原子吸收光谱法（AAS）之外的一种可行的、不太复杂的砷测定方法。原子吸收光谱法（以及其他竞争方法）只能在实验室中进行，而阳极剥离伏安法可在实验室中常规使用，也可使用 946 便携式 VA 分析仪在野外进行。测定在 scTRACE 金电极上进行。

Arsenic is ubiquitous in the earth’s crust in low concentrations. Elevated levels can be found in mineral deposits and ores. Arsenic from such deposits leaches into the groundwater in the form of arsenite (AsO33-) and arsenate (AsO43-), causing its contamination. In addition to the arsenic originating from natural sources, industry and agriculture contribute to the contamination to a lower extent. The guideline value for inorganic total arsenic in the World Health Organization’s «Guidelines for Drinking-water Quality» is set to 10 μg/L.

With a limit of detection (LOD) of 0.9 μg/L, anodic stripping voltammetry is a viable, less sophisticated alternative to atomic absorption spectroscopy (AAS) for the determination of arsenic. While AAS (and competing methods) can only be performed in a laboratory, anodic stripping voltammetry can be used conventionally in the laboratory or alternatively in the field using the 946 Portable VA Analyzer. The determination is carried out on the scTRACE Gold electrode.

Bottled mineral water

Figure 1. 946 Portable VA Analyzer (scTRACE Gold version)

The scTRACE Gold is electrochemically activated prior to the first determination. In the next step, the water sample and the supporting electrolyte are pipetted into the measuring vessel. The determination of arsenic is carried out with the 884 Professional VA or with the 946 Portable VA Analyzer using the parameters specified in Table 1. The concentration is determined by two additions of an arsenic standard addition solution.

Figure 2. 884 Professional VA fully automated for VA
Table 1. Parameters
Parameter Setting
Mode SQW – Square wave
Deposition potential -1 V
Deposition time 60 s
Start potential -0.3 V
End potential 0.4 V
Peak potential As 0V
  • scTRACE Gold

With a 60 s deposition time, this method is suitable for the determination of arsenic in water samples in concentrations from β(As(total)) = 0.9–10 μg/L.

Figure 3. Determination of arsenic in bottled mineral water (946 Portable VA Analyzer; 60 s deposition time)
Table 2. Results of the determination of As in mineral water
Sample As (μg/L)
Bottled mineral water 4.4

Application Bulletin 416: Determination of arsenic in water with the scTRACE Gold

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