Complexometric Titration Mainly Using

A decrease in pH will reduce the concentration of the complexing species. Hence the formation of E.D.T.A. complexes with metal ions is best carried out in alkaline solutions. 

When pM(= -log[M ], is plotted against volume of E.D.T.A. used for titration, a sharp rise indicates the end-point. Changes in pM can be detected by using indicators which form complexes with specific metal ions. The complexes differ in colour from the free indicator and there is a sudden colour change at the end-point, when the E.D.T.A. has completely complexed (preferentially) the metal ions, thus liberating the free indicator. 

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Oxyacids, like citric or tartaric acids, and polyols, like saccharose are also used, mainly as masking agents, in qualitative analysis. The action of some specific reagents, like oc-a -bipyridyl for iron(II) and dimethylglyoxime for nickel(II), is also based on the formation of chelate complexes. In quantitative analysis the formation of chelates is frequently utilized (complexometric titrations). ... 

Complexometric titrations are mainly used to determine the concentration of cations in solution. The method is based on the competition between a metal ion (for example) and two ligands, one of which acts as an indicator and the other is a component of a standard solution. 

Potentiometric titration is actually a form of the multiple known subtraction method. The main advantage of titration procedures, similar to multiple addition techniques in general, is the improved precision, especially at high determinand concentrations. ISEs are suitable for end-point indication in all combination titrations (acid-base, precipitation, complexometric), provided that either the titrand or the titrant is sensed by an ISE. If both the titrant and the titrand are electro-inactive, an electrometric indicator must be added (for example Fe ion can be titrated with EDTA using the fluoride ISE when a small amount of fluoride is added to the sample solution [126]). 

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