Name: trace analysis by stripping voltammetry
Uploaded: 2024-12-05T18:31:57.000Z
Duration: 1 min 13 s
Channel: JoVE

溶出伏安法涉及将痕量金属分析物沉积在电极表面，随后通过监测电流随施加电位的变化，进行溶出过程——阳极溶出、阴极溶出或吸附溶出。
阳极溶出伏安法包含两个步骤。首先，对工作电极施加一个恒定的阴极电位，使离子被还原为相应的金属并沉积在电极上。
接下来，当施加阳极电位时，沉积的金属被氧化至其离子状态，并从电极表面溶出。所测得的阳极电流与样品中待测物的浓度成正比。
阴极溶出伏安法涉及汞电极的氧化，该电极与分析物结合并沉积为不溶性薄膜。通过向更负的电位方向扫描，将沉积物重新溶出进入溶液，并测量阴极电流。
吸附溶出伏安法涉及分析物在电极表面的吸附，而无需发生电解，随后进行阳极或阴极溶出。

伏安法：溶出法

Voltammetry: Stripping Methods

阳极溶出伏安法 (ASV)、阴极溶出伏安法 (CSV) 和吸附溶出伏安法 (AdSV) 是用于测定溶液中痕量分析物的电化学技术。这些方法涉及向电极施加电位并测量产生的电流。


 阳极溶出伏安法 (ASV)


 ASV 用于测定痕量金属和准金属。它涉及两个步骤：沉积和溶出。首先，将负电位施加到工作电极，还原分析物离子并将其沉积在电极表面。沉积步骤后，沿正方向扫描电位，使沉积的分析物离子氧化并从电极表面溶出。测量并绘制这些过程中产生的电流，显示与分析物浓度的比例关系。

<ul style="padding-left: 35px; list-style: disc;">
<li>最佳条件：确保电极表面清洁且抛光良好，控制沉积时间，并保持溶液中稳定的 pH 值。</li>
<li>挑战：其他离子的干扰、电极结垢以及对精确电位控制的需求。</li>
</ul>

 阴极溶出伏安法 (CSV)


 在 CSV 中，汞电极在与分析物相互作用时发生氧化，在其表面形成不溶性薄膜。之后，沿负方向扫描电位，减少并溶出电极表面的分析物。测量产生的电流，该电流与分析物浓度成正比。CSV 通常用于测定有机化合物，例如某些污染物和药物。

<ul style="padding-left: 35px; list-style: disc;">
<li>最佳条件：选择合适的支持电解质并保持适当的温度控制。</li>
<li>挑战：由于汞电极具有毒性，需要对其进行处理，并确保可重复形成薄膜。</li>
</ul>

 吸附溶出伏安法 (AdSV)


 AdSV 是溶出伏安法的一种变体，其中分析物物质在溶出步骤之前吸附到电极表面上。将电位施加到工作电极上，导致分析物物质的吸附。吸附后，通过改变电位将分析物从电极上溶出，并测量产生的电流以量化分析物浓度。AdSV 通常用于测定有机和无机物种，包括各种污染物、杀虫剂和重金属。

<ul style="padding-left: 35px; list-style: disc;">
<li>最佳条件：选择合适的吸附时间、电位和电极材料。</li>
<li>挑战：电极上吸附位点的竞争和对溶液中杂质的敏感性。</li>
</ul>

阳极溶出伏安法（ASV）、阴极溶出伏安法（CSV）和吸附溶出伏安法（AdSV）是三种常用的电化学分析技术，用于……

Education

教育

JoVE Core

Analytical Chemistry

分析化学

Unit 1

第一单元

Electrochemical Analyses and Redox Titration

电化学分析与氧化还原滴定

electrochemical-analyses-and-redox-titration

KEY TERMS AND CONCEPTS

关键术语与概念

trace analysis by stripping voltammetry

Stripping voltammetry is an electrochemical method used to detect trace amounts of analytes in solution. It works by applying a potential to an electrode and measuring the current that results. The current is then used to estimate the analyte concentration.

Anodic Stripping Voltammetry, or ASV, is used for metals and metalloids at very low levels. It has two main steps: deposition and stripping. First, a negative potential reduces analyte ions and deposits them on the working electrode surface. Then the potential is scanned in the positive direction, and the deposited ions oxidize and strip off the surface. The measured current is proportional to the analyte concentration. A clean, well-polished electrode surface, controlled deposition time, and stable pH help ASV work well. Common problems include interference from other ions, electrode fouling, and the need for precise control of potential.

Cathodic Stripping Voltammetry, or CSV, uses a different stripping step. In this method, a mercury electrode is oxidized while it interacts with the analyte, which forms an insoluble film on the surface. The potential is then scanned in the negative direction, reducing and stripping the analyte from the electrode. The current that appears is proportional to analyte concentration. CSV is often used for organic compounds, including some pollutants and drugs. It works best with the right supporting electrolyte and good temperature control. Its challenges include the toxicity of mercury and the need for reproducible film formation.

Adsorptive Stripping Voltammetry, or AdSV, depends on adsorption before stripping. Adsorption means the analyte species stick to the electrode surface. After this step, the potential is changed and the analyte is stripped off, and the resulting current is measured to find the concentration. AdSV can be used for organic and inorganic species, including pollutants, pesticides, and heavy metals. The method depends on the right adsorption time, potential, and electrode material. It can also be affected by competition for adsorption sites and by impurities in the solution.

Trace Analysis by Stripping Voltammetry

electrochemistry: overview

Electrochemistry and Redox Reactions

Electrochemistry connects electrical measurements with chemical reactions, especially oxidation and reduction. It focuses on how electron movement helps explain reaction behavior. Oxidation is the loss of electrons from a substance, and reduction is the gain of electrons. A species with strong electron affinity is an oxidizing agent, or oxidant. A species that donates electrons is a reducing agent, or reductant. These redox steps are often described with half-reactions. When electrons move...

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Types of Electrodes in Electrochemistry

Electrodes are conductive materials in an electrochemical cell. They allow electron transfer reactions to happen at their surfaces. Electrochemical measurements use them to control and measure current and potential. The working electrode, also called the indicator electrode, is the main sensing electrode. Its potential changes with the analyte concentration and with the activity of the electroactive species. Common indicator electrodes include inert platinum electrodes, silver electrodes that...

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Static and dynamic electrochemical methods study what happens at the boundary between an electrode and a solution. These interfacial methods focus on the electrode-solution interface rather than the overall properties of the liquid. They are useful in electroanalytical chemistry because they can detect very small changes in analyte concentration. These methods are grouped by whether a nonzero current flows through the cell. Static methods, such as potentiometry, measure the cell potential...

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Reference and Indicator Electrodes in Potentiometry

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Membrane Electrodes in Ion Sensing

Membrane electrodes measure ions by using a selective membrane that creates a potential difference across it. This membrane potential is called the asymmetry potential, and it can remain nonzero even when analyte concentrations are the same on both sides of the membrane. The signal usually depends on all ions in the sample that can interact with the membrane, not just one analyte. Selectivity is described by a selectivity coefficient. This value compares the response to an interferent with the...

redox titration: overview

Redox Titration Endpoints and Indicators

Redox titration uses electron transfer in a redox, or reduction-oxidation, reaction to find the concentration of an unknown solution. The titrant has a known concentration, and it is added gradually to the analyte, which is the solution being tested. The endpoint shows when the reaction between the two substances is complete. Before a redox titration begins, the analyte should be in a single oxidation state. If needed, this is done by pre-oxidizing or pre-reducing the sample with an auxiliary...

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Using Iodine to Find Unknown Concentrations

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Choosing Oxidizing Titrants in Redox Titration

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Endpoint Detection in Potentiometric Titration

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Gran Plot for Titration Endpoint Prediction

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Electrode Weighing in Electrogravimetric Analysis

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Coulometry and Electrical Charge Analysis

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Measuring Analyte Charge by Potentiostatic Coulometry

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Controlled-Current Coulometry in Redox Analysis

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Electrically Generated Reagents in Titration

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Voltammetry for Detecting Redox Species

Voltammetry measures current in an electrochemical cell as the applied potential changes. It is an electroanalytical method used to study redox-active species. The current response is shown on a graph called a voltammogram. A voltammetric cell uses three electrodes: a working electrode, a reference electrode, and an auxiliary electrode. Redox reactions happen at the working electrode, and a potentiostat controls its potential. The reference electrode, such as a saturated calomel electrode or a...

voltammetry: factors affecting measurements

voltammetry-factors-affecting-measurements

Voltammetry and Faradaic Current

Voltammetry measures faradaic current, which is the current created by redox reactions of an analyte at the working and auxiliary electrodes. The current from reduction is called cathodic current and carries a positive charge. The current from oxidation is called anodic current and has a negative charge. The applied potential at the working electrode controls the flow of faradaic current. The size of that current depends on how fast the oxidation or reduction reaction occurs at the electrode...

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Voltammogram Shapes and Redox Analysis

Voltammograms are current plots made against applied potential. They help show how an electrochemical system behaves during a redox reaction. The shape of the plot depends on how the current is measured and on whether convection, or fluid movement, is present. When convection is present, as in hydrodynamic voltammetry, the voltammogram usually has a sigmoid shape. In this case, the current rises from a residual current to a limiting current at the analyte’s oxidation or reduction potential.

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Polarography and Voltammetry with Mercury Drops

Polarography and hydrodynamic voltammetry are voltammetric techniques used to study electrochemical reactions. They track the current that flows as the electrode potential changes. In polarography, the key working electrode is a dropping mercury electrode, or DME. A DME uses a capillary tube filled with mercury. A tiny mercury droplet forms at the tip and then drops away. This gives a fresh electrode surface for each measurement. During the test, the potential applied to the DME changes...

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Pulse Voltage Methods for Electrochemistry

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Reading Redox Peaks with Cyclic Voltammetry

Cyclic voltammetry measures how current changes as the potential at an electrode is varied. It is used to study the redox properties of a chemical species, meaning how easily it is oxidized or reduced. The setup uses three electrodes in an electrolyte solution. The working electrode is where the redox reaction of interest takes place. The reference electrode provides a stable potential, and the counter electrode completes the circuit for current flow. The process starts at a chosen initial...

voltammetry: stripping methods

Stripping voltammetry is an electrochemical method used to detect trace amounts of analytes in solution. It works by applying a potential to an electrode and measuring the current that results. The current is then used to estimate the analyte concentration. Anodic Stripping Voltammetry, or ASV, is used for metals and metalloids at very low levels. It has two main steps: deposition and stripping. First, a negative potential reduces analyte ions and deposits them on the working electrode surface.

amperometry: overview

Measuring Analytes with Amperometric Sensors

Amperometry measures specific analytes in a solution by tracking the electric current from an electrochemical reaction. A constant potential is applied between a working electrode and a reference electrode. The current that results is proportional to the analyte concentration. The Clark oxygen electrode is a common example of amperometry. It uses a cathode and an anode sealed inside a gas-permeable membrane. The cathode is typically platinum or gold, and the anode is silver. When a potential...

key terms and concepts

Learn how ASV, CSV, and AdSV detect trace analytes by measuring current changes at an electrode, with uses, setup needs, and common challenges.

Trace Analysis by Stripping Voltammetry | JoVE K12

analytical chemistry

JoVE Core Analytical Chemistry simplifies complex chemical principles by breaking them down into clear, engaging animations, making topics from SI Units to NMR spectroscopy more accessible and straightforward. Additionally, the scientist-in-action videos highlight the application of these concepts in real-world research conducted in laboratories globally.

Trace Analysis by Stripping Voltammetry

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