Electrochemical elimination methods

The article reviews two non-conventional electrochemical methods - eliminat ion polarography (EP) and elimination voltammetry with linear scan (EVLS). The two methods enable elimination of selected particular currents, contrib uting to the measured total current. The most frequently eliminated particu lar currents are the charging current (I-c), the diffusion current (I-d), a nd 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 linea r combination of the direct current and its time derivative and/or time int egral. In EVLS, eliminated currents are expressed as I = const. v(x), and e limination is achieved by a function obtained by linear combination of tota l currents measured at different scan rates v. The theory of EP and EVLS ha s been verified experimentally. In comparison with d.c. polarography and li near sweep voltammetry, both elimination methods have the following advanta ges: (a) an expanded available electrode potential range, (b) increased cur rent sensitivity and (c) improved signal resolution. In EVLS, (b) and (c) r esult 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 i s particularly pronounced in the case of an adsorbed substance. Application of EP and EVLS enables detection of minor electrode processes overlapped b y a major one, such as desorption process during reduction, or the formatio n of associates which influence the process of hydrogen evolution. In addit ion, both methods improve the sensitivity of determination of electroactive substances, and may contribute to solving problems associated with complex electrode processes.