Application of Elimination Methods in Electrochemical Study of DNA
Non-conventional electrochemical methods, such as elimination polarography (EP) and elimination voltammetry with linear scan (EVLS) provide the elimination of selected particular currents, forming the measured total current. The most frequently eliminated particular currents are the charging current (Ic), the diffusion current (Id), and the kinetic current (Ik). In EP the elimination is achieved by function formed by a linear combination of the direct current and its time derivative and/or integral; eliminated currents are expressed as I=const.tx. In EVLS the elimination proceeds by function formed by a linear combination of total currents measured at different scan rates; eliminated currents are expressed as I=const.vx.
The theoretical results of EP and EVLS have been experimentally verified for the case of reversible and irreversible processes and for the potential range expansion [3-6]. The substantial advantages, provided by elimination methods in comparison with classical polarography and linear sweep voltammetry are: (a) the expansion of available electrode potential range (study of processes of nucleic acid bases near the process of hydrogen evolution), (b) the increase of current sensitivity (analytical applications for DNA), (c) the improvement of the peak distinction (adenine and cytosine). In EVLS the advantages, (b) and (c), result from the fact that the elimination of Ic and Ik currents decreases the irreversible current width and increases the peak height. This effect is particularly pronounced in the case of an adsorbed substance and was experimentally confirmed by DNA study . While the LSV signal of single-stranded DNA at low concentration gives a slight hint in the cathodic process of adenine and cytosine residues, the elimination of Icand Ikprovides quite a clear signal in the form of the peak-counterpeak, which enables the determination of DNA at concentrations below microgram per milliliter. The results received by the adsorptive stripping voltammetry in the mode of linear scan (LSV), square-wave (SWV) and elimination with linear scan (EVLS) are compared and discussed.
This work was supported by grant 204/97/K084 from the Grant Agency of the Czech Republic.
 O. Dracka, Collect. Czech. Chem. Commun., 51 (1986) 288-294.
L. Trnkova, R. Kizek1, O. Dracka2
Department of Theoretical and Physical Chemistry, Faculty of Science,