dsDNA modified carbon nanofiber-solidified paste electrodes: Probing Ni(II)-dsDNA interactions

In order to develop a renewable electrode surface, carbon nanofibers (CNF) were embedded into solidified paste electrodes using a composite of paraffin wax and paraffin oil. A range of different compositions was surveyed and the optimal composition of the paste for electroanalysis was found to be 43% of CNF, 41% of paraffin wax, and 16% of paraffin oil. The electrochemical properties of the novel composite electrode were investigated using cyclic voltammetry and electrochemical impedance spectroscopy and compared to those of similar graphite-solidified paste electrodes. The carbon nanofibers enhance the activity of the surface of the electrode and provide a good substrate for the adsorption and voltammetric detection of dsDNA. Responses of dsDNA bases and Ni²⁺ ions accumulated from ammonium buffer pH 8.5 (with a Langmuirian binding constant of 10⁵ mol^-1 L) were investigated and a limit of detection of 7 nmol L^-1 (at 3σ) was obtained using "nucleation stripping voltammetry". Interferences by other metal cations are examined and discussed.