Module for rapid normal and inverse normal pulse polarography: application to study of adsorption

Construction and utilization of a module for interfacing with a rapid response potentiostat are described, which permits use of normal pulse polarography (NPP) and inverse normal pulse polarography (INPP). In trace analysis by NPP, the module permits micromolar detection. INPP is shown to be very useful for adsorption studies, e.g., the relative surface excess ([Gamma])---potential profile can be rapidly obtained. The influence of time between pulse application and current sampling (discharge time, td) on signal level and response profile is discussed. A td as short as 0.57 ms was tested for both techniques; shorter td intervals may be possible. The electronic operation is described in sufficient detail to allow ready alteration of the circuitry shown for interfacing to most potentiostats. Applicability of the module is illustrated by examination of the adsorption of adenine at the mercury electrode/aqueous solution interface.