Titration is used in analytical chemistry to determine the amount or concentration of a substance, known as the analyte. Titration is a quantitative measurement of an analyte in solution by its complete reaction with a reagent. In a titration, one reagent (the titrant) is slowly added to a solution containing the species being measured (the analyte). As it is added, a chemical reaction occurs between the titrant and analyte. The point at which the reaction is complete and an equivalent quantity of titrant and analyte are present (a stoichiometric equivalent) is called the equivalence point. This can be determined by a chemical indicator that is also present in the solution, or by a measurable physical change in the solution, like pH, electrode potential, conductivity, or light absorption (color). In practice, an abrupt change of this physical property signals the end of titration, called the endpoint. The purpose of titration is to determine the quantity or concentration of an analyte with a known concentration and volume of a titrant. Titrations are based on chemical reactions which must fulfill four requirements: • The reaction between the analyte and the titrant must occur quickly, without a secondary reaction • The reaction must go to completion • The reaction must have well-known stoichiometry (reaction ratio) • Must have a convenient method of endpoint detection Titrations are highly precise and can provide many advantages over alternative methods. Titrations are quickly performed and require relatively simple apparatus and instrumentation. Automatic Titration Automatic titration is done with instrumentation that delivers the titrant, stops at the endpoint and calculates the concentration of the analyte automatically. Automatic titrators are best for accurate and repeatable results, as an electrochemical measurement is used to determine the endpoint as opposed to a subjective color indicator. Analyses that can be performed by potentiometric automatic titrators include: • Acid-base titrations • Oxidation reduction titrations • Complexometric titrations • Precipitation titrations • Non-aqueous titrations • Argentometric titrations • pH, ORP and Ion selective measurements Analyses performed by bivoltammetric automatic titrators include: • Coulometric Karl Fischer titration (trace amounts of water determination) • Volumetric Karl Fischer titration (greater than 100 ppm water determination) Hanna Instruments® Titration Systems 4 Titration 4.2 | www.hannainst.com introduction
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