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Analysis of the instrument in the electrochemical properties of a class of substances in solution based on the establishment, by German chemist C. Winkler, first introduced in the 19th century in the field of analysis, the instrument The analysis began in 1922 with the Czech chemist J. Halovsky establishing the polarographic method. Electroanalytical Techniques

Electroanalytical Chemistry

Usually, the test solution is used as an integral part of the chemical battery. There is a certain relationship between the electrical parameters of the battery (such as resistance, conductance, potential, current, electric quantity or current-voltage curve) and the concentration of the measured substance. The method of performing the measurement.

 Introduction

Electroanalytical Chemistry Lecture Notes: Electroanalytical methods are one of the important components of instrumental analysis. It is based on the electrochemical properties and variation of substance in solution, based on potential, conductance basic electrical quantities, current and power of some other measuring a relationship between the amount of the test substance on, for component qualitative And quantitative instrumental analysis methods, also known as Electroanalytical Chemistry.

Classification

Electrochemical analysis systems have different classifications based on different classification conditions. The following are several common classifications:

   1. According to the relationship between the physical potential of the electrode potential, the electric quantity, the current voltage, and the conductance and the concentration of the solution in a chemical battery under a certain condition.

For example, potentiometry, potentiostatic coulometry, polarography, and conductance.

   2. A physical quantity such as electrode potential, electric quantity, current, and conductance in a chemical battery: a mutation is used as a method of indicating an endpoint.

For example, potentiometric titration, coulometric titration, current titration, and conductometric titration.

   3. A certain component in the test solution is reacted through the electrode to precipitate a metal or an oxide on the working electrode and the mass of the electrodeposit is weighed to obtain the content of the component to be measured. Electroanalytical Techniques

For example, electrolytic analysis.

What are Electroanalytical Methods?

Conductance method

It is a method of directly measuring the the conductivity of an electrolyte solution using a conductivity meter.

Potentiometric titration

In the process of titrating the ion to be measured with the standard solution, indicating the arrival of the endpoint of the titration with the potential change of the indicating electrode is a test method combining the potential measurement and the titration analysis.

Electrolysis analysis

The DC voltage is applied to the two electrodes of the electrolytic cell and the content of the measured object is calculated according to the increased mass of the electrode. Electroanalytical Techniques

Voltammetry

A method of analyzing according to a current-voltage curve (volt-ampere curve) in an electrolysis process.

Stripping voltammetry

A polarographic analysis method combining a potentiostatic electrolysis enrichment method with voltammetry.

It first electrolyzes the substance to be tested at a suitable potential and concentrates it on a special electrode with a fixed surface area, then reverses the potential, re-dissolves the material enriched on the electrode, and records the current-voltage curve. Quantitative analysis was performed based on the magnitude of the elution peak current.

Potentiometric stripping analysis

The material to be tested is electrolyzed and concentrated on the working electrode at a constant potential, and then the constant potential circuit is disconnected, and the enriched substance is dissolved by the oxidant in the electrolyte, and the potential time curve at the time of dissolution is recorded, according to the curve.

Electroanalytical Chemistry2

The length of the dissolution step is quantified. This method is abbreviated as P. S. A.

The main difference between the potentiometric stripping analysis and the stripping voltammetry is that the former has no current flowing through the working electrode during dissolution, while the latter has a background current, which in some cases may flood the dissolution peak.

Characteristics

Electrochemical analysis has The next feature.



1. sensitivity is higher. The minimum analytical detection limit can reach 10-12mol/L.

  2. accuracy high. For example, Coulometric analysis and electrolytic analysis are highly accurate, the former is particularly suitable for the determination of trace components, and the latter is suitable for the determination of high content components.

    3. measuring range is wide. Potentiometric analysis and micro coulometric analysis can be used for the determination of trace components; electrolytic analysis, capacitance analysis, and coulometric analysis can be used for the analysis of medium content components and pure substances.

  4. The instrument is simple and inexpensive, the instrument is easy to debug and operate, and it is easy to automate.

    5. Poor selectivity. The selectivity of electrochemical analysis is generally poor, but the selectivity of ion selective electrode method, polarographic method, and controlled cathode potential electrolysis is higher.

Electrochemical analysis can be divided into conductivity analysis, potential analysis, voltammetry, and polarographic analysis, electrolysis and coulometric analysis, depending on the measured electrical quantity.

Development History

The development of electroanalytical chemistry has a long history and is closely related to the development of cutting-edge science and technology and disciplines.

Modern electroanalytical chemistry not only analyzes the composition and composition of components but also plays an important role in the development of electrode process theory, life sciences, energy science, information science, and environmental science.

electroanalytical

As an analytical method, as early as the 18th century, electrolytic analysis and coulometric titration occurred.

In the 19th century, conductometric titration, pH measurement of glass electrodes and high-frequency titration were observed.

In 1922, the publication of the polarographic a method marked the beginning of a new phase in the development of electrical analysis methods.

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In the 1960s, ion-selective electrodes and enzyme-immobilized enzyme electrodes were successively produced.

In the 1970s, after the development of various biosensors not only limited to the enzyme system, the generation of microelectrode voltammetry extended the space-time range of electroanalytical chemistry research, and adapted to the needs of biological analysis and life science development. Electroanalytical Techniques

Throughout the development of electroanalytical chemistry in the world today, the United States has the strongest electroanalytical chemistry, and its research focuses on the frontiers of scientific and technological development, involving bioelectrochemistry directly related to life sciences; and electrochemical sensors related to the environment of energy, information, materials, etc. And to detect and study the spectral electrochemistry of electrochemical processes.

The Czech Republic and the former Soviet Union have a good foundation for electrochemical research at the liquid-liquid interface.

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Tokyo, Japan, Kyoto University is very distinctive in bioelectrochemical analysis, surface modification and characterization, electrochemical sensors and new methods of electrical analysis.

Some universities in the UK focus on the research of spectroelectrochemistry, electrochemical thermodynamics, and kinetics and chemically modified electrodes.

  There are two reasons for polarization: concentration polarization and electrochemical polarization.

1. Concentration polarization: When a current flows through the electrode, the concentration of ionsin the solution cannot keep up with the reaction speed of the electrode, so that the ion concentration near the surface of the electrode is different from that in the bulk solution, so that when a current flows through the electrode.

The phenomenon that the electrode potential value deviates from the equilibrium electrode potential is called concentration polarization.

current voltage

2.  Electrochemical polarization: Due to the limited reaction speed of the electrode, the degree of electrification on the electrode isdifferent from that in the equilibrium, and the phenomenon that the electrode potential value when the current passes has deviated from the equilibrium electrode potential is called electrochemical polarization.

Application

    (1) Electrochemical analysis can be used not only for quantitative analysis of material composition and content but also for structural analysis, such as elemental valence and morphological analysis.

    (2) The traditional electrochemical analysis method is mainly used for the analysis of inorganic ions. With the development of such technologies, the application of measuring organic compounds is also increasingly widespread, and the application in drug analysis is also increasing. Electroanalytical Techniques

    (3) With the continuous advancement of electrode manufacturing technology, the ultra-micro electrode directly penetrates into the living body, and the living body analysis becomes a reality.

   (4) Electrochemical analysis can also be used as a tool for scientific research, such as chemical equilibrium constant measurement, chemical reaction mechanism research, research on electrode process kinetics, redox process, catalytic reaction process, organic electrode process, adsorption phenomenon and the like.

   (5) Electrochemical analysis method also plays an important role in environmental monitoring and control, industrial automatic control and online analysis because of its easy signal transmission, easy automation, and continuous operation, and simple instrument and low price.

Electroanalytical chemistry is the science of characterization and measurement using the electrical and electrochemical properties of matter. It is an important component of the disciplines of electrochemistry and analytical chemistry, with other disciplines such as physics, electronics, computer science, materials science, and biology.

There is a close relationship between learning and so on. Electroanalytical chemistry has established a relatively complete theoretical system.

Electroanalytical Techniques

Electroanalytical chemistry is not only an important branch of modern analytical chemistry but also a surface science, playing an increasingly important role in the study of surface phenomena and phase interfaces.

1.  Electroanalytical Chemistry is a recognized method for rapid, sensitive and accurate micro and traces analysis. The concentration of heavy metal ions can be as low as 10-12mol/L by stripping voltammetry.

The sensitivity can be 10-14mol/L by combined catalysis. If the specific catalytic reaction of the biological enzyme is combined, the detection limit can reach 10-16mol. /L, electroanalytical instruments are simple and inexpensive, especially in organic, biological and pharmaceutical, environmental analysis and more and more show great potential and superiority.

electroElectroanalytical Techniqueschemistry

Also, Electrochemical methods are also very useful in harsh environmental conditions such as flowing rivers, non-aqueous chemical flow processes, lava, and nuclear reactor core fluids.

2. The study of electrode process kinetics and electrode reaction mechanism is another important aspect of electroanalytical chemistry.

The electrode process often involves chemical steps, the formation of new phases, and surface diffusion steps in solution or on the surface of the electrode. Electroanalytical Techniques

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The study of electrode process kinetics is of great significance in metallurgy, electroplating, electrosynthesis of organic and inorganic materials, chemical power sources, chemical sensors, and corrosion protection of metal materials.

3. The redox reaction mechanism of the substance on the electrode is very complicated, but its research results can be used for reference in many disciplines, especially in the fields of biochemistry and pharmacology.

For example, the metabolic process of a drug in the human body is a biological redox process with some similarities to the redox the reaction of the drug on the electrode. Electroanalytical Techniques

From the mechanism of the electrode reaction, the biological redox process of these drugs can be understood. It can also study the effects of heat, light, oxygen, wine, acid, and alkali on biological processes, study joint effects, synergistic effects and anti-resistance, study the effects of common substances in the human body, etc., for the clinical application and pharmacological effects of drugs. The research provides a theoretical basis.