Mathematical modelling of potentiometric stripping analysis. Chemical stripping in quiet solutions

A mathematical model of batch potentiometric stripping analysis is proposed. It describes the case when the plating of the Hg electrode and the electrodeposition of the analyte take place in a mechanically stirred measuring cell while the chemical stripping step takes place in the same solution but without stirring. Between the electrodeposition step and the chemical stripping steps there is a period during which the moving solution is allowed to settle completely. Potentiometric stripping experiments with standard solutions of Pb(II) in 0.1 M hydrochloric acid were performed at 15 and 60 s settling times. The good agreement between the experimental results and the predictions of the model confirm its validity and show that it can be used successfully for better understanding and optimisation of batch potentiometric stripping systems where the chemical stripping takes place without mechanical stirring. Depending on the requirements for sample throughput and sensitivity of a particular analysis, the appropriate size of the MF electrode and the duration of the settling time can be easily selected using model simulations.