Endpoint detection conductometric

As with amperometric titrations, to have straight-line portions of the titration curve dilution corrections must be made because the response is directly dependent on the concentration of the ionic species. Also, the important data are taken before and after the equivalence point rather than precisely at the equivalence point. The general conditions for effective conductometric measurements of solutions are discussed in Chapter 5 and are directly applicable when the system is used as the endpoint detection method. A particularly complete review of the subject has been presented.8... 

The electromotoric force (emf) of a cell depends on the ionic concentration of the solutions. To locate the equivalence point, the variation in emf is monitored as the concentration of the analyte changes. When the measured emf is plotted against the total volume of titrant added, the curve produced is similar to that of a titration curve Fig. 4. This technique has all the advantages of the conductometric method and gives an experimental curve from which the endpoint can be detected accurately. 

The means of detecting the endpoint will be dictated by the type of reaction employed. Acid-base titrations are most easily followed using a glass pH electrode while redox reactions lend themselves to amperometric detection (only a small fraction of the species detected is consumed at the indicator electrode). Other options are ion-selective electrodes and conductometric detection. 

Electrical methods of determining the end-point of titrations are widely used some of the advantages of the technique are obvious, such as the ability to titrate coloured solutions where the change of a visual indicator would be difficult or impossible to detect and the ability to carry out titrations for which no suitable visual indicator exists. Electrometric endpoints may often be employed with greater accuracy than visual ones and with greater sensitivity. It should always be remembered, however, that where a suitable visual method of end-point detection is available, it is usually more rapid and more economical to use. Electrometric methods may be classified into potentiometric, conductometric and amperometric methods. 

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