Adsorptive stripping voltammetry of denatured DNA on Hg/Ag electrode
In this work the voltammetric behavior of denatured DNA in aqueous 0.3 M NaCl + 50 mM Na2HPO4 on a hemispherical Hg/Ag electrode (MSE) of about a 0.5 mm diameter is compared with that on a classical hanging mercury drop electrode (Hh IDE). The comparison was done by measuring the differential capacities of the electrodes, the square-wave and the differential pulse voltammetric curves. The considerably lower capacity values of MSE's in the positive polarization region were probably due to the higher adsorptivity of chlorides. In agreement with the literature, in presence of DNA two capacitance peaks were obtained ascribed to segmental desorption or reorientation of the helical regions. The faradaic voltammetric signal was considered to be due to reduction of adenine and cytosine residues in the measured solution. The application of the more user-friendly and sturdy construction of the Hg/Ag electrode required an appropriate electrochemical pretreatment of the electrode/solution interface, During the described measuring procedure the results obtained on the different interfaces of Hg/Ag and HMDE electrodes differed; however, the reproducibility and the sensitivity of measurements were better with the renewed HMDE.