Evaluation of different carbon electrodes for adsorptive stripping analysis of nucleic acids

Recently we have shown (see Ref. [8]) that submicrogram amounts of nucleic acids can be measured by potentiometric stripping analysis (PSA) at carbon paste electrodes. In this article we investigate and compare various carbon electrode materials for use in stripping analysis of nucleic acids. Both the interfacial and redox properties of DNA and RNA are strongly dependent upon the nature of the carbon material and the electrode pretreatment step. In view of the high solvent decomposition background response near the guanine oxidation peak, only potentiometric stripping analysis can be used for convenient quantitation of trace levels (ng/mL) of nucleic acids. The trend in sensitivity: carbon paste > pyrolytic graphite > highly oriented pyrolytic graphite > carbon strip [with detection limits for oligo(dG)(20) of 20, 30, 40 and 50 ng/mL, respectively, using 5 min accumulation]. No response was observed for trace measurements at the glassy carbon or carbon fiber electrodes. The influence of the surface pretreatment and accumulation time is described along with the analytical-performance characteristics at each electrode. Useful information about the adsorption behavior of nucleic acids at different carbon electrodes are also obtained.