Electrochemical oxidation of biological molecules at carbon paste electrodes pre-treated in guanine solutions.

Carbon paste electrodes were modified in guanine solutions under an applied potential of 1.1 V and used for electrochemical detection of NADH, NADPH, uric acid and 8-oxoguanine. Detection limits were 3.3, 3.7, 6.6 and 2.0 x 10(-6) M, respectively, with sensitivity of 0.13, 0.10, 0.26 and 0.40 A mol(-1) l cm(-2), respectively. The electrodes showed high reproducibility and absence of surface poisoning effects. Good analytical performance was attributed to the formation of superficial dimer or trimers species of guanine during the modification process.