饮用水中的铅

AN-V-214

2020-09

Straightforward determination by voltammetry using a gold microwire electrode

众所周知，铅对人体有剧毒，因为它会干扰酶的反应。铅从管道系统渗入饮用水中可导致慢性铅中毒。目前，世界卫生组织的《饮用水水质指南》中规定的暂定指导值最大浓度为 10 μg/L。阳极剥离伏安法的检出限（LOD）为 0.2 μg/L，是原子吸收光谱法（AAS）的一种可行的、不太复杂的替代方法，可用于检测饮用水中的铅含量。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 便携式重金属快速分析仪在现场进行。在 scTRACE 金电极上的银膜上进行测定。

Lead is known to be highly toxic to humans as it interferes with enzyme reactions. Chronic lead poisoning can be caused by Pb leaching into drinking water from piping systems. The current provisional guideline for lead in the World Health Organization’s «Guidelines for Drinking-water Quality» sets a maximum concentration of 10 μg/L.

With a limit of detection (LOD) of 0.2 μg/L, anodic stripping voltammetry using the scTRACE Gold is a viable, less sophisticated alternative to atomic absorption spectroscopy (AAS) to determine lead in drinking water. While AAS (and competing methods) can only be performed in a laboratory, anodic stripping voltammetry can be used conventionally in the laboratory with the Metrohm 884 Professional VA or alternatively in the field with the 946 Portable VA Analyzer.

The determination is carried out on a silver film applied to the scTRACE Gold electrode. It is a combined sensor consisting of a gold microwire working electrode, Ag/AgCl reference electrode, and carbon auxiliary electrode on a ceramic substrate. It is easy to handle and needs no extensive maintenance such as mechanical polishing.

Figure 1. 946 Portable VA Analyzer

The water sample is pipetted into the measuring vessel. Citric acid buffer is added as supporting electrolyte. The determination of lead can be carried out on the 946 Portable VA Analyzer or on the 884 Professional VA using the scTRACE Gold sensor via anodic stripping voltammetry using the parameters listed in Table 1. The lead concentration is determined by two additions of lead standard addition solution.

The scTRACE Gold is modified with a silver film prior to the determination of lead. The silver film is electrochemically deposited from a silver solution.

Figure 2. 884 Professional VA

**Table 1.** Parameters
Parameter	Setting
Mode	SQW – Square wave
Deposition potential	-0.7 V
Deposition time	90 s
Start potential	-0.7 V
End potential	0 V
Peak potential Pb	-0.48 V

The method is suitable for the determination of lead concentrations in unpolluted water samples in concentrations up to 30 μg/L. The limit of detection of the method is approximately 1 μg/L.