图片来源：Metrohm AG
重金属离子的准确量化对于许多应用，例如废物管理，环境监测，研究或某些临床测试至关重要。尽管重金属确实发生了，但在过去的200年中，城市化和工业化的增加导致许多环境中的重金属水平增加。
As these hazardous elements are released they accumulate in soil, surface, or groundwater, potentially entering the food chain via drinking water or bioaccumulation in animals and plants. In fact, pregnant women are advised against eating seafood due to the potential for mercury (Hg) accumulation via the food chain.
金属的类型将确定其毒性程度，生物学作用，最关键的是其浓度。饮用水中的铁，镉，铅，铜，铜，砷或镍的浓度是人类中毒的最常见原因。
为了强调某些重金属的毒性并保护人类健康，世界卫生组织（WHO），美国环境保护署（EPA）和欧洲委员会等组织都有针对水平的限制或指南值饮用水中的重金属。
图片来源：Metrohm AG
A number of techniques have been developed for heavy metal ion analysis previously. Commonly used techniques include inductively coupled plasma (ICP), atomic absorption spectrometry (AAS), or fluorescence spectrometry.
这些技术中的每一个都需要昂贵的设备，以及大量的维护成本和训练有素的人员。app亚博体育因此，显然需要直接，成本效益且高度敏感的方法检测水样中的金属离子。
Stripping voltammetryoffers an ideal solution for these challenges, providing a rapid, simple, and inexpensive alternative to many other techniques. Stripping voltammetry is accessible to untrained personnel while being able to accommodate detection limits in the ng/L range. Furthermore, it can determine trace levels of heavy metals in the field, making stripping voltammetry an interesting, valuable method for mobile applications.
The Principle of Stripping Voltammetry
重金属的伏安测定涉及两个步骤。第一步涉及分析物在工作电极的表面上被预召集，如图1所示，使用阳极剥离伏安测定铅（PB）的示例。
图1。阳极剥离伏安法 - 铅沉积（溶液搅拌）。图片来源：Metrohm AG
Step two is the stripping step (Figure 2), and it is here that the analyte is released via either reduction or oxidation, depending on the method used for determination. It is this step that generates the analytical signal, which must be proportional to the amount of analyte deposited.
图2。Anodic stripping voltammetry – stripping of lead (solutionnot搅动）。图片来源：Metrohm AG
As well as anodic stripping voltammetry, adsorptive stripping voltammetry or cathodic stripping voltammetry also function in a similar fashion.
这些不同的方法中的每一个都有一个共同的特征：伏安确定仅与测量中使用的传感器一样好。
需要新传感器
Research on new sensors in voltammetry tends to be triggered by environmental issues, sensor costs, and an ongoing need for heavy metal ion determination in the field.
Ideally, new sensors will be manufactured from inexpensive, non-toxic materials. These materials’ properties can lead to some restrictions, however. One issue is the limited number of elements that it is possible to detect on a certain electrode material like carbon, gold, or bismuth.
Successfully determining the number of elements simultaneously at the same mercury-free sensor can also be problematic, but this can be addressed through careful selection of the most appropriate electrode material along with an optimal sensor design.
Bismuth as an Alternative Electrode Material
与汞相比，有许多尝试定位有毒电极材料较少的尝试，适用于重金属离子的测定。亚博网站下载不幸的是，这些材料都没有达到高水平的电积分性能。亚博网站下载在2000年，一位名叫约瑟夫·王（Joseph Wang）的美国研究人员成为第一个报告鞭毛胶片电极的人。
图3。Bismuth crystal. Image Credit: Metrohm AG
Following this revolutionary initial report, there has been a marked increase in the use of bismuth-based electrodes prepared as in-situ and ex-situ films onsolid-state electrodessuch as carbon.
Bismuth’s low toxicity and broad electrochemical window are key factors, as well as bismuth’s ability to form alloys with a high number of heavy metals. Bismuth also shows high hydrogen overpotential, similar to that of mercury.
These properties combine to make bismuth a particularly interesting option for stripping voltammetry. Hydrogen evolution is suppressed efficiently, meaning that noise-free measurements at negative potentials may be performed.
Bismuth electrodes based on bismuth films are a viable option, but the need for film deposition adds an extra, time-consuming step to the overall process.
New Sensor in VA: The Bi Drop Electrode
得益于BI滴电极的发展，现在有一个新型的固态电极可用，适用于测定饮用水中的重金属离子。直径约2 mm的二滴下降可提供伏安测量中的工作电极。
电极可以在没有膜沉积或抛光的情况下起作用 - 仅需要电化学激活。这将整个分析时间降低了相当大的量，一旦激活，在低μg/l，甚至NG/L范围内的一系列高度可重复的重金属测定变得可行。
The Bi drop electrode facilitates mercury-free monitoring of the limit values of the heavy metals lead, cobalt, cadmium, nickel, and iron in drinking water. Because the electrode does not necessitate mechanical treatment, it is particularly useful in online applications. A further benefit of the Bi drop electrode is the fact that lead and cadmium, or cobalt and nickel can be simultaneously determined.
图4。Bismuth drop electrode from Metrohm. Image Credit: Metrohm AG
该传感器稳定，具有成本效益，高度敏感，并且可以比以前研究的基于二晶的电极提供更多可再现的结果。
In order to properly demonstrate the flexibility and range of possibilities offered by the Bi drop electrode, the following sections explore examples of anodic stripping voltammetry, adsorptive stripping voltammetry, and direct voltammetric determination.
Applications
镉的阳极剥离测定镉和铅
世界卫生组织的饮用水质量指南set a maximum concentration of 3 µg/L for cadmium and 10 µg/L for lead in drinking water. These provisional guidelines aim to mitigate the toxic effects of cadmium on the kidneys, skeleton, and respiratory system, and the neurotoxic effects of lead.
The Bi drop electrode is mercury-free and is able to facilitate simultaneous determination of lead and cadmium in drinking water with no supplementary film plating step. A limit of detection (LOD) of 0.5 µg/L for lead and 0.1 µg/L for cadmium can be achieved with a 60 second deposition time - exceptional sensitivity which is more than sufficient to monitor the aforementioned provisional guideline values from the WHO.
图5。Example for determination of cadmium and lead in tap water spiked with β(Cd) = 2 µg/L and β(Pb) = 2 µg/L. Image Credit: Metrohm AG
这种令人印象深刻的灵敏度与准确性和可重复性相结合。检查标准溶液中10个测量值的相对标准偏差（β（cd）= 1 µg/l和β（pb）= 5 µg/l）为5％和3％，回收率为100％和90％分别用于铅和镉。
直接测定铁
饮用水中存在的铁可能会导致红棕色的污渍和令人不愉快的金属味道。铁细菌可以在含有100 µg/l铁的水中生长，从而产生红棕色的粘液，可能导致进攻性气味或堵塞管道。
不溶性铁沉积物可能会在长时间内形成。这可能会在许多农业和工业应用中引起持续的问题，包括系统冷却，供水或现场灌溉。为了避免这些问题，美国环境保护局（EPA）已将水加工和处理厂的次要最大污染物水平（SMCL）定义为饮用水中的300 µg/l铁。
在非毒性BI滴电极上的三乙醇胺复合物的伏安测定过程中，无需富集。该系统利用催化信号增强功能，以非常低的水平检测，检测极限为5 µg/L，以及在高达500 µg/L的浓度范围内的测量值。
Figure 6.用β（Fe）= 20 µg/L的自来水中的铁测定的示例。图片来源：Metrohm AG
这种方法是工艺分析仪或自动化系统的理想选择，可在大型样本系列中提供稳定的结果并完全自动化铁。在检查标准溶液中（β（fe）= 50 µg/l）中一系列10个测量值的相对标准偏差为3％，而回收率为111％。
Adsorptive Stripping Voltammetric Determination of Nickel and Cobalt
Metallurgical operations, electroplating processes, and leaching from fittings and pipes are all primary sources of nickel pollutions. Catalysts employed in the chemical and petroleum industries are key application fields for cobalt.
Metal from each of these sources is either released directly or through the wastewater-river pathway and into the drinking water system. Because of this, EU legislation stipulates 20 µg/L as the limit value for nickel concentration in drinking water.
Adsorptive stripping voltammetry（ADSV）构成了简单，同时确定钴和镍的基础。
与ADSV结合使用的无毒BI Drop Electrode的独特性能可实现出色的灵敏度和性能。30秒沉积时间的检测极限约为钴的0.1 µg/L，镍的检测时间为0.2 µg/L。这可以通过增加沉积时间进一步降低。
Figure 7.Determination of nickel and cobalt in tap water spiked with β(Ni) = 0.5 µg/L and β(Co) = 0.5 µg/L. Image Credit: Metrohm AG
This approach is best suited for automated systems or process analyzers, enabling automatic determination of these metals in large sample series, as well as providing accurate, stable results.
Relative standard deviation for 10 successive measurements in a check standard solution (β(Ni) = 1 µg/L β(Co) = 1 µg/L) is 4% and 5%. The recovery rate is 88% for cobalt and 106% for nickel.
Key Features of the Bi Drop Electrode
总而言之，BI Drop Electrode提供以下关键功能：
- 无毒，无汞的替代品理想的痕量金属测定
- 同时确定CO和NI，以及PB和CD
- 低μg/L和Ng/L范围内的检测极限
- Ideal for online and automated systems
Acknowledgments
由最初由Metrohm Al亚博网站下载yson Lanciki撰写的材料生产。
This information has been sourced, reviewed and adapted from materials provided by Metrohm AG.
For more information on this source, please visitMetrohm AG.