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

스트리핑 전압전류법은 전극 표면에 미량 금속 분석물을 증착하는 것을 포함합니다. 그 다음에는 양극, 음극 또는 흡착성 스트리핑이 이어지며, 이는 전류가 적용된 전위의 함수로 모니터링될 때 발생합니다.
양극 스트리핑 전압전류법은 두 단계를 포함합니다. 먼저, 작동 전극에 일정한 음극 전위가 가해져 이온이 전극에 증착된 해당 금속으로 감소합니다.
다음으로, 양극 전위가 적용됨에 따라 증착된 금속은 이온 상태로 산화되고 전극 표면에서 벗겨집니다. 측정된 결과 양극 전류는 샘플의 분석물 농도에 비례합니다.
음극 스트리핑 전압전류법은 수은 전극이 분석물과 결합하여 불용성 필름으로 증착되는 것을 포함합니다. 이것은 더 많은 음의 전위를 향해 스캔하고 음극 전류를 측정하여 솔루션으로 다시 제거됩니다.
흡착 스트리핑 전압전류법은 전기분해를 거치지 않고 전극 표면에 분석물을 흡착한 후 양극 또는 음극 스트리핑을 수행하는 것입니다.

전압전류법: 스트리핑 방법

Voltammetry: Stripping Methods

양극 스트리핑 전압전류법(ASV), 음극 스트리핑 전압전류법(CSV), 흡착 스트리핑 전압전류법(AdSV)은 용액에서 미량의 분석물을 결정하는 데 사용되는 전기화학적 기술입니다. 이러한 방법에는 전극에 전위를 적용하고 결과 전류를 측정하는 것이 포함됩니다.

양극 스트리핑 전압전류법(ASV)

ASV는 미량 수준의 금속 및 준금속을 결정하는 데 사용됩니다. 증착과 스트리핑의 두 단계가 포함됩니다. 먼저, 음전위를 작업 전극에 적용하여 분석물 이온을 환원시키고 전극 표면에 증착합니다. 증착 단계 후 전위를 양전위로 스캔하여 증착된 분석물 이온이 산화되어 전극 표면에서 제거되도록 합니다. 이러한 프로세스 동안 발생하는 전류를 측정하여 그래프로 표시하여 분석물 농도와의 비례 관계를 보여줍니다.

최적 조건: 전극 표면을 깨끗하고 잘 연마하고 증착 시간을 제어하며 용액에서 안정적인 pH를 유지합니다.

난제: 다른 이온의 간섭, 전극 오염 및 정밀한 전위 제어의 필요성.

음극 스트리핑 전압전류법(CSV)

CSV에서 수은 전극은 분석물과 상호 작용하는 동안 산화되어 표면에 불용성 필름을 생성합니다. 그런 다음 전위가 음의 방향으로 스캔되어 전극 표면에서 분석물이 감소하고 스트립됩니다. 결과 전류가 측정되며 분석물 농도에 비례합니다. CSV는 일반적으로 특정 오염 물질 및 약물과 같은 유기 화합물을 결정하는 데 사용됩니다.

최적 조건: 적절한 지지 전해질을 선택하고 적절한 온도 제어를 유지합니다.

난제: 독성으로 인해 수은 전극을 취급하고 필름 형성이 재현 가능하도록 합니다.

흡착 스트리핑 전압전류법(AdSV)

AdSV는 스트리핑 전압전류법의 변형으로, 스트리핑 단계 전에 분석물 종이 전극 표면에 흡착됩니다. 작동 전극에 전위가 적용되어 분석물 종이 흡착됩니다. 흡착 후, 전위를 변경하여 전극에서 분석물을 제거하고, 그 결과 전류를 측정하여 분석물 농도를 정량화합니다. AdSV는 일반적으로 다양한 오염 물질, 살충제, 중금속을 포함하여 유기 및 무기 종을 결정하는 데 사용됩니다.

최적 조건: 적절한 흡착 시간, 전위, 전극 재료를 선택합니다.

난제: 전극의 흡착 부위에 대한 경쟁과 용액의 불순물에 대한 민감성.

ASV(Anodic Stripping Voltammetry), CSV(Cathodic Stripping Voltammetry) 및 Adsorptive Stripping Voltammetry(AdSV)는 사용되는 전기화학 기술입니다.

Education

교육

JoVE Core

Analytical Chemistry

분석 화학

Unit 1

제1단원

Electrochemical Analyses and Redox Titration

전기화학적 분석 및 산화-환원 적정

electrochemical-analyses-and-redox-titration

KEY TERMS AND CONCEPTS

주요 용어 및 개념

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...

interfacial electrochemical methods: overview

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Static and Dynamic Electrochemical Methods

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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Potentiometry and Electrochemical Cell Potential

Potentiometry measures the potential difference between two electrodes in an electrochemical cell. It does this without drawing significant current, so the solution’s composition is not altered. The method uses an indicator electrode, which exchanges electrons with the analyte solution, and a reference electrode, which keeps a constant potential. Each electrode is placed in a solution that makes up a half-cell. In a common setup, the reference electrode is the anode, or left-hand electrode,...

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Reference and Indicator Electrodes in Potentiometry

Potentiometric measurements use reference electrodes and indicator electrodes to track changes in a solution. A reference electrode gives a stable baseline, while indicator and working electrodes respond to changes in the solution’s composition. The Standard Hydrogen Electrode, or SHE, is a common reference electrode. It keeps a zero potential at all temperatures. However, it needs a continuous supply of hydrogen gas, so it is not practical for routine use. The Saturated Calomel Electrode, or...

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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

Iodometry and iodimetry use iodine to measure unknown concentrations in redox titrations. These methods help determine the amount of an oxidizing or reducing agent in a sample. The key idea is that iodine changes color and reacts in a known stoichiometric ratio with the analyte. In iodometric titrations, the sample usually contains an oxidizing agent. The solution is acidified and then treated with an excess of iodide ions, which releases an equivalent amount of iodine in equilibrium with...

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redox-titration-other-oxidizing-and-reducing-agents

Choosing Oxidizing Titrants in Redox Titration

Redox titrations can use oxidizing titrants other than iodine. Common choices include potassium permanganate (KMnO4), cerium(IV), and potassium dichromate (K2Cr2O7). The best titrant depends on stability, cost, analyte strength, and the reaction rate between the analyte and the titrant. Potassium permanganate is a strong oxidizing titrant in highly acidic solution. It reduces from Mn(VII) to Mn(II) while it oxidizes the analyte to a higher oxidation state. KMnO4 also works as a self-indicator,...

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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

Electrogravimetric analysis measures an analyte by weighing the material that deposits on an electrode. A pre-weighed working electrode is placed in solution, and a potential is applied. The target substance then deposits by reduction at the cathode or by oxidation at the anode. After electrolysis, the electrode is weighed again. The mass increase gives the weight of the analyte in the solution. To check that deposition is complete, the fresh electrode surface is exposed to the solution while...

coulometry: overview

Coulometry and Electrical Charge Analysis

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Measuring Analyte Charge by Potentiostatic Coulometry

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controlled-current coulometry: overview

Controlled-Current Coulometry in Redox Analysis

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Electrically Generated Reagents in Titration

Coulometric titrations use an electrically generated reagent to measure the amount of a substance in a sample. The electron acts as the standard reagent, and the result depends on the current and the time used to generate it. The method follows the same basic idea as a regular titration, including endpoint detection. Two conditions are essential for this type of titration. First, the electrode reaction that makes the reagent must be 100% efficient. Second, the generated reagent must react...

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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...

voltammograms: overview

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

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Pulse Voltage Methods for Electrochemistry

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Reading Redox Peaks with Cyclic Voltammetry

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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

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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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