Abstract
Differential pulse polarography (DPP) is an excellent analytical method, but cannot be recommended for applications in the initial stages of mechanistic studies. Its application is also questionable in the analysis of samples containing varying concentrations of an organic cosolvent or of surface active compounds. The effect on limiting currents obtained by DC polarography and on peak currents obtained by DPP was demonstrated for reductions of various nitrobenzene derivatives. The similarity of changes in current for various nitrobenzenes enables the exclusion of the formation of adducts or micelles as the predominant effect. The decrease of the limiting currents in all cases is much smaller than the decrease of DPP peak currents, due to strong effects of the surfactants on the kinetics of electroreduction. For the analysis of natural products or of solutions containing varying amounts of organic cosolvent, the measurement of the DC polarographic limiting current is preferred. An addition of 30% ethanol minimizes the effects of the varying concentration of surfactant on both DC polarographic limiting and DPP peak currents.