Fourier Analysis of AC Polarography. Elimination of Non-Faradaic Effects and Determination of Kinetic Parameters for Cd(II)-Na2SO4 System

The on-line Fourier analysis of the AC polarographic current was found to give accurate results for electrode kinetics provided that the compensation of the iR drop and of the non-faradaic current was attained: The iR drop was compensated by a positive feedback technique. The charging current was cancelled by addition of a pseudo-charging current, inverse in phase to the former. Both the phase angles and amplitudes of the fundamental and second harmonic AC responses for the system of Pb(II) in 1M NaClO4 ([H+]=12 mM) agreed with theoretical prediction. As an illustration, the kinetic parameters of Cd(II)-1 n Na2SO4 system have been determined to be ks=(0.20±0.03) cm/s and α=0.30 (0.27<0.30<0.35) from the second harmonic AC polarogram.