Abstract
The consequences of adsorption of the electroactive species in analytical pulse polarography are discussed. For both normal pulse polarography (NPP) and differential pulse polarography (DPP) explanations are given in terms of the concentration profiles as they are developed upon adsorption before pulse application. An approximate interpretation of the depressed NPP limiting current is sometimes possible by taking its dependence on pulse duration into account. In a number of cases NPP offers the possibility of avoiding adsorption effects by choosing a suitable initial potential. In DPP reactant adsorption generally causes peak enlargement, but the theoretical approach is complex and practical means for checking or eliminating adsorption effects in DPP are limited. Analytical calibration curves start with a linear portion corresponding with the linear adsorption regime; at higher concentrations the DPP curve bends downwards, whereas the NPP curve bends slightly upwards, before reaching the linear region of diffusion control. Several analytical pitfalls connected with the adsorption phenomena are indicated.
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