Amperometry:

In Polarography, we have seen that in a particular polarogram, the limiting current of an electroactive substance, at a suitable (fixed) potential depends on the substance concentration only. If we decrease the concentration of the electroactive substance by its interaction with another substance, the current will be decreased. This principle is made to get the equivalence point by measuring the current flowing at an indicator electrode. This technique is known as amperometric titration. Therefore, amperometry named after the unit of current, "ampere" is totally based on the measurement of current when the voltage across the electrodes of a cell is kept constant. In amperometric titrations the current passing through the cell (containing the anal yte) at a suitable constant voltage is measured as a function of the volume of titrant (or of time if the titrant is generated by a constant current coulometric process). Through far, the application of amperometry is in amperometric titrations.

Amperometric titrations are more accurate than voltammetric methods. Furthermore, this titration can be performed even when the substance being determined is not reactive, since an equally satisfactory equivalent point can be located with either a reactive titrant or when the product is reactive. Modifications have been made by the use of amperometric indicators. At plotting the data for current vs volume of titrant, we get straight lines having different slopes. The equivalence point is obtained by extrapolation of the linear segments to their intersection. The microelectrode (that is, the indicator electrode) may be a

i) dme or

ii)  a solid state platinum electrode or

iii)  a rotating platinum electrode or

iv) an electrode of some other inert material

One can dispense with a reference electrode by the use of twin microelectrode procedure called biamperometry or earlier known as dead-stop end point titration.