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This paper describes voltamperometry on solid electrodes of various geometries, adapted to the study of insoluble, unstable or confined species. It covers: thin- voltamperometry (complete electrolysis of a confined species), the study of species adsorbed or confined in polymer films (closed systems voltamperometry on graphite paste electrodes (analysis of poorly soluble solids), rotating disc and voltamperometry (detection of reactive intermediates) and voltamperometry on ultramicroelectrodes, offering high spatial resolution, low ohmic drop and compatibility with poorly conducting media.
Differential or pulse techniques are variants of solid electrode voltammetry, in which the applied potential is modulated in a specific way to improve the detection of faradic current while reducing the signal component related to capacitive current. This article describes the main techniques (normal pulse voltammetry, constant or increasing amplitude superimposed pulse voltammetry, and square wave differential voltammetry) that offer a crucial improvement in measurement sensitivity, better resolution, and a better signal-to-noise ratio.
The aim of this article is to describe the evolution of voltammograms of electrochemical systems by the action of chemical reagents (electroactive or not) present in solution. Under certain conditions, this evolution can consist of a simple translation of the voltammograms along the potential axis and/or an amplification of the electrolysis intensity, depending on the chemical reactivity involved. These voltammogram modification characteristics can therefore be indicative of the presence of a non-electroactive reagent and enable its content to be determined indirectly. The study is limited to solid electrodes.
Chronopotentiometry is a measurement of potential, as a function of time, the excitation signal being constant or variable in time, but not zero, and the transfer of matter being ensured by diffusion. The article presents the theory and the different applications of chronoamperometry: - with monotonic imposed current, it is widely used for electrode characterization and study of reaction mechanisms - with cyclic or alternating current for the study of complex systems, - with pulse trains, for the determination of thermodynamic properties and interdiffusion coefficients of alloys.
This article deals with the theoretical basis of the current-potential characteristics at a solid electrode of simple redox couples (noted Red/Ox) in solution, by considering on the one hand the kinetics of electron transfer at the electrode/solution interface, and on the other hand the intervention of the transport of material in solution both in the stationary convective diffusion regime and in the pure natural diffusion regime. This article also presents the essential guidelines for the experimental implementation of the studied voltammetric techniques (electrode materials, equipment, domain of electroactivity, etc.).
Potentiometry is an easy-to-implement, fast, and accurate physicochemical analysis method and remains the most common electrochemical method (pH electrodes, selective electrodes, etc.). Advances in electronics, automation of measurements, and the development of liquid membrane electrodes and then solid-state electrodes have facilitated the development of this method. The general principles of this method, the concepts of activity and electrochemical potential, have been reviewed in this paper in order to introduce the basic laws of potentiometry. The operating principles of reference electrodes and indicator electrodes are detailed before presenting some specific electrodes.
Potentiometry allows two main types of measurement: pH and ion or molecule concentration. This article describes the electrodes that allow these measurements. The hydrogen electrode, quinhydrone electrode, antimony electrode, glass electrode, and pH ISFET are described for pH measurements. In the case of ion concentration measurement, the operation of ion indicator electrodes is based either on the exploitation of a redox potential or a membrane potential. The problem of selectivity and the impact on the measurement of the presence of other ions is also addressed. Dissolved gas indicator electrodes have also been described.
This paper contains selected applications to browse various fields of applications of GC. Examples involve different sample preparation techniques, injection methods, columns and hyphenation to various detectors to perform the best separations of complex mixtures as possible.
This article presents methods for characterizing powders or porous materials based on mercury porosimetry. The physical phenomena underlying these methods are described and interpreted on a thermodynamic level. The main experimental procedures are then presented, detailing the influence of the experimental conditions on the results obtained. The latter are interpreted by taking into account the complexity of the capillary phenomena which lead to intrusion-extrusion hysteresis and the impact of the main relevant parameters. The exploitation of the data in terms of pore size distribution, porosity or density is detailed and compared to other technics.
Gas Chromatography (GC) is the separation method of choice for the analysis of volatile and semi-volatile compounds. It is based on the difference of distribution of compounds between a thin film of a stationary phase deposited in a long-fused silica capillary column and a gas used as the mobile phase. This article describes the fundamentals of GC while a large part is devoted to the essential parts of the chromatograph: the main stationary phases and columns are described together with the injectors and, last but not least, the detectors. Detectors are mandatory to detect and identify the compounds when the elute from the column after their separation.
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