Coulometry indirect

Flame photometry Atomic absorption spectrometry Amperometry/coulometry Indirect potentiometry... 

Measurements of the adsorption of inhibitors on corroding metals are best carried out using the direct methods of radio-tracer detection and solution depletion measurements . These methods provide unambiguous information on uptake, whereas the corrosion reactions may interfere with the indirect methods of adsorption determination, such as double layer capacity measurements", coulometry", ellipsometry and reflectivity Nevertheless, double layer capacity measurements have been widely used for the determination of inhibitor adsorption on corroding metals, with apparently consistent results, though the interpretation may not be straightforward in some cases. 

In coulometry, one measures the number of coulombs required to convert the analyte specifically and completely by means of direct or indirect electrolysis. 

In electroanalysis, coulometry is an important method in which the analyte is specifically and completely converted via a direct or indirect electrolysis, and the amount of electricity (in coulombs) consumed thereby is measured. According to this definition there are two alternatives (1) the analyte participates in the electrode reaction (primary or direct electrolysis), or (2) the analyte reacts with the reagent, generated (secondary or indirect electrolysis) either internally or externally. 

Mediators are occasionally termed mediator titrants or auxiliary redox couples, while mediation is sometimes called indirect coulometry. The efficiency of the reaction shown in equation (5.8) is assumed to be 100%, and so, in practice, the coulometric experiment is performed in the same way as if direct electron transfer occurred - the charge required to reduce (or oxidize) the mediator is determined, and Faraday s laws are then applied. 

Undoubtedly, while the direct method is more relevant, because the analyte activity in water plasma is actually measured, the reporting on blood sodium, potassium and chloride in terms of concentration in plasma is preferred by medical professionals, whatever method of measurement is used. This is justified by the fact that before ISEs had been invented, sodium, potassium and chloride were all determined by indirect methods, with flame emission spectroscopy (FES) for Na+ and K+, and coulometry for Cl. ... 

For monitoring catalytic (enzymatic) products, various techniques, such as spectrophotometry [32], potentiometry [33,34], coulometry [35,36] and amperometry [37,38], have been proposed. An advantage of these sensors is their high selectivity. However, time and thermal instability of the enzyme, the need of a substrate use and indirect determination of urea (logarithmic dependence of a signal upon concentration while measuring pH) cause difficulties in the use and storage of sensors. 

Coulometry is based on direct or indirect electrochemical transformation of the determined substance. For a complete electrochemical transformation of amount of substance n of the substance determined, we need electric charge Q quantitatively described by the Faraday law ... 

There are two methods of electrochcmically reducing acetylenes, namely, direct charge transfer to the triple bond from the cathode and the electrolytic generation of an intermediate which attacks the acetylene. The first method (direct reduction) has the advantage that mechanistic studies using, for example, cyclic voltammetry and coulometry can be carried out, while the second method (indirect reduction) appears to offer more scope for product control and has been more extensively investigated. 

The methods of coulometry are based on the measurement of the quantity of electricity involved in an electrochemical electrolysis reaction. This quantity is expressed in coulombs and it represents the product of the current in amperes by the duration of the current flow in seconds. The quantity of electricity thus determined represents, through the laws of Faraday, the equivalents of reactant associated with the electrochemical reaction taking place at the electrode of significance. In the analytical chemistry sense, the process of coulometry, carried out to the quantitative reaction of the analyte in question, either directly or indirectly, will yield the number of analyte equivalents involved in the sample under test. This will lead to a quantitative determination of the analyte in the sample. Analytical coulometry can be carried out either directly or indirectly. In the former the analyte usually reacts directly at the surface of either the anode or cathode of the electrolysis cell. In the latter, the analyte reacts indirectly with a reactant produced by electrolytic action at one of the electrodes in the electrolysis cell. In either case, the determination will hinge on the number of coulombs consumed in the analytical process. 

These methods, which to our knowledge are only used in vitro, enables the determination of a compound by its complete oxidation or reduction on a macroelectrode at a fixed potential or current current is integrated till the electrochemical detection of the final point. Coulometry may be either direct if the analyte is electroactive, such as seric iron, or indirect the electrogenerated reagent may then be ... 

Bromine also exhibits the property to fix itself on some organic structures. This can be achieved either by substitution or by addition. The compound to determinate is faced with a solution of bromine in excess, bromine being generated previously by the reaction bromate/bromide or by coulometry. Bromine in excess is determined by indirect iodometry. Of all the titrations involving the bromine element, they are the most numerous. 

It has long been popular to make use of the properties of volt-ammetric current-potential or current-time curves to detect and study the kinetic complications accompanying certain electrolytic processes occurring at micro-electrodes. Such studies have, in some cases, suffered from the fact that only minute quantities of reaction products can be accumulated during reasonable electrolysis times. In many cases, therefore, the characterization of possible secondary reactions and identification of reaction intermediates and products has had to rest primarily on indirect evidence. Controlled-potential coulometry, on the other hand, can provide semi-micro or macro scale electrolyses while retaining the specificity of the primary electrolysis process. 

---