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Electrochemical Composition Measurement
Published in John G. Webster, Halit Eren, Measurement, Instrumentation, and Sensors Handbook, 2017
Michael J. Schöning, Arshak Poghossian, Olaf Glück, Marion Thust
Coulometry represents an electroanalytical method, where the analyte is specifically and completely converted due to direct or indirect electrolysis. The quantity of electricity (in coulombs) consumed by this reaction, the charge, is measured. A fundamental requirement of coulometry is that the species in the solution interact with 100% current efficiency; that is, the reaction corresponds to the Faraday law. According to this condition, there exist two alternatives: the analyte participates in the electrode reaction (primary or direct coulometric analysis) and the analyte reacts with a reagent, generated by an electrode reaction (secondary or indirect coulometric analysis). Two general techniques—controlled-potential coulometry and coulometric titration (controlled-current coulometry)—are used for coulometric analysis.
Voltametric, Amperometric, and Other Electrochemical Analyzers
Published in Béla G. Lipták, Analytical Instrumentation, 2018
Because the coulomb provides a direct connection through Faraday’s law between reaction current and analyte concentration during a redox process, coulometry offers a direct method of determining analyte concentration. Two types of coulometry are possible: constant current and controlled potential. Constant current coulometry depends on analyte oxidation/reduction to support the specified current flow. When the supply of material is insufficient to carry this current, the electrode potential drifts until another reaction begins. The result of this process is a potential time relationship similar to the results obtained in chronopotentiometry, and the amount of charge passed is simply the product of the constant current and electrolysis time.
Detector Characterization
Published in Alan Owens, Semiconductor Radiation Detectors, 2019
Classical wet chemical techniques, based on gravimetry, titrimetry and electrochemistry can meet precision and accuracy requirements; these are commonly used for analysis of major elements and stoichiometry. Although tedious and time consuming, they are unaffected by the electrical properties of the element of interest as opposed to electrical methods in which information is restricted to elements of electro-active form while those of electro-inactive or electrically compensated species cannot be effectively determined. Conventional gravimetry, based on the weight of a reaction product, and titrimetry, based on the amount of a standard solution consumed in a reaction, can achieve precisions of ± 0.1%; with refinements in technique, this can be further extended to ± 0.01%. Coulometry is an electrochemical method based on the quantitative measurement of electric charge resulting from the quantitative electrochemical conversion of a constituent in the solution from one initial oxidation state to another well-defined oxidation state. Since electrons are essentially being used as the measured reagent, this method is capable of very high precision and accuracy. The most precise determination of stoichiometry is based on constant current coulometry, in which a reliability of 0.001%–0.01% can be obtained. Yang et al. [1], used constant potential and constant current coulometry in a stoichiometric analysis of several (III-V and II-VI) binary compounds, such as GaAs, CdTe and HgxCd1-xTe and ternary (1-III-VI) compounds such as CuInS2, CuInSe2 and CuGaxIn1-xSeyTe2-y. They found that precisions of < 0.3% could be readily obtained.
New analytical methods for the determination of sulfur species with microextraction techniques: a review
Published in Journal of Sulfur Chemistry, 2022
Arina Skok, Yaroslav Bazel, Andriy Vishnikin
Summarizing what has thus far been presented, the need for further development and improvement of methods for determining sulfur and its compounds in various objects of analysis, taking into account modern requirements and capabilities of detection techniques and sample preparation, becomes clear. The literature describes various methods for determining the forms of sulfur, including spectroscopic methods (UV-Vis spectrometry, luminescence spectroscopy, atomic emission spectrometry, mass spectrometry), electroanalytical methods (voltammetry, potentiometry, coulometry), liquid chromatography and gas chromatography, etc.