AMPEROMETRIC TITRATIONS
In amperometric titrations, the voltage applied across the indicator electrode and
reference electrode is kept constant and the current passing through the cell is measured
and plotted against the volume of reagent added. In these titrations, the current passing
through the cell between an indicator electrode and a reference electrode at a suitable
constant voltage is measured as a function of the volume of the titrating reagent. As the
diffusion current is a consequence of polarisation at a micro electrode, the technique is
also known as polarographic or polarometric titration. By using this method, electro
reducible and nonreducible analytes can be determined.
There are four types of titrations
(a) Reducible analyte Vs non reducible reagent
eg. Pb2+ Vs SO42-
At -0.8 v, Pb2+ + 2e- Pb(s)
At the end point, PbSO4 is formed
Decrease current due to decrease in conc. of Pb2+ ions in solution due ppt as lead
sulphate
(b) Non reducible sample Vs reducible reagent
eg. Cl- Vs Ag+
Initially Cl- ions (nonreducible), no current flows and AgCl is precipitated. After end
point current increases due to excess Ag+
ie,
Ag+ + e- Ag(S)
In amperometric titrations, the voltage applied across the indicator electrode and
reference electrode is kept constant and the current passing through the cell is measured
and plotted against the volume of reagent added. In these titrations, the current passing
through the cell between an indicator electrode and a reference electrode at a suitable
constant voltage is measured as a function of the volume of the titrating reagent. As the
diffusion current is a consequence of polarisation at a micro electrode, the technique is
also known as polarographic or polarometric titration. By using this method, electro
reducible and nonreducible analytes can be determined.
There are four types of titrations
(a) Reducible analyte Vs non reducible reagent
eg. Pb2+ Vs SO42-
At -0.8 v, Pb2+ + 2e- Pb(s)
At the end point, PbSO4 is formed
Decrease current due to decrease in conc. of Pb2+ ions in solution due ppt as lead
sulphate
(b) Non reducible sample Vs reducible reagent
eg. Cl- Vs Ag+
Initially Cl- ions (nonreducible), no current flows and AgCl is precipitated. After end
point current increases due to excess Ag+
ie,
Ag+ + e- Ag(S)
