Electrochemical Elimination Methods

Abstrakt

The article reviews two non-conventional electrochemical methods - elimination polarography (EP) and elimination voltammetry with linear scan (EVLS). The two methods enable elimination of selected particular currents, contributing to the measured total current. The most frequently eliminated particular currents are the charging current (I_c), the diffusion current (I_d), and the kinetic current (I_k). In EP, eliminated currents are expressed as I = const.t^x, and elimination is achieved by a function obtained by linear combination of the direct current and its time derivative and/or time integral. In EVLS, eliminated currents are expressed as I = const.v^x, and elimination is achieved by a function obtained by linear combination of total currents measured at different scan rates . The theory of EP and EVLS has been verified experimentally. In comparison with d.c. polarography and linear sweep voltammetry, both elimination methods have the following advantages: (a) an expanded available electrode potential range, (b) increased current sensitivity and (c) improved signal resolution. In EVLS, (b) and (c) result from the fact that the elimination of I_c and I_k currents decreases the irreversible current width and increases the peak height. This effect is particularly pronounced in the case of an adsorbed substance. Application of EP and EVLS enables detection of minor electrode processes overlapped by a major one, such as desorption process during reduction, or the formation of associates which influence the process of hydrogen evolution. In addition, both methods improve the sensitivity of determination of electroactive substances, and may contribute to solving problems associated with complex electrode processes.