Simultaneous determination of guanine and adenine contents in DNA, RNA andsynthetic oligonucleotides using a chemically modified electrode

Simultaneous determination of guanine and adenine contents in DNA, RNA and synthetic oligonucleotides an a Nafion-ruthenium oxide pyrochlore modified electrode is described. This chemically modified electrode shows very prono unced electrocatalytic effects towards the oxidation of guanine and adenine . The experimental parameters for individual determinations of guanine and adenine on the modified electrode were first optimised. Excellent detection limits (S/N = 3) of 0.86 ng ml(-1) (5.7 nM) and 2.7 ng ml(-1) (20 nM) for guanine and adenine, respectively, were obtained. Simultaneous determinatio n of guanine and adenine in a mixture was also optimised. The denatured cal f thymus DNA and yeast RNA showed oxidation peaks corresponding to guanine and adenine with a linear calibration line up to 5 mu g ml(-1) in pH 4.0 ph osphate buffer. The detection limit estimated for these nucleic acids were 11.5 ng ml(-1) and 37.7 ng ml(-1) for guanine and adenine, respectively. Th e new method provides an alternative to estimate the guanine and adenine co ntents more selectively and sensitively than currently applied techniques.