Coulométrique

Coulométrique refers to a set of analytical techniques used in electrochemistry that rely on measuring the quantity of electricity required to completely electrolyze a sample. This quantity of electricity, measured in coulombs, is directly proportional to the amount of substance that has reacted. The fundamental principle behind coulometric methods is Faraday's laws of electrolysis, which establish a quantitative relationship between the amount of chemical change produced and the quantity of electricity passed.

There are two main types of coulometric analysis: coulometry at controlled potential and coulometry at controlled current. In coulometry at controlled potential, the electrode potential is held constant, and the current is monitored over time. The current decreases as the electroactive species is consumed. The total charge passed is obtained by integrating the current-time curve. In coulometry at controlled current, also known as amperostatic coulometry or electrogravimetry, a constant current is applied. The time required for the complete electrolysis is measured. Both methods require precise measurement of charge or time and a quantitative electrochemical reaction.

Coulometric techniques offer high accuracy and precision, often considered among the most accurate quantitative methods available. They are particularly useful for determining trace amounts of substances and for validating other analytical methods. Applications include the determination of water content (Karl Fischer titration is a coulometric method), assay of high-purity materials, and analysis of pharmaceuticals and environmental samples. The selectivity of coulometry can be achieved by controlling the electrode potential.