Low-potential amperometric determination of purine derivatives through surface oxide regeneration method

This article described a novel amperometry which can be used for determination of purine derivatives including uric acid, xanthine, hypoxanthine, guanine, and adenine without surface contamination. By applying a constant potential of -0.125 V (vs. Ag/AgCl) in a flow injection system, the chelating capability of these purine derivatives converts the cuprous oxide layer into a soluble complex. This behavior would dissolve the passive oxide layer and expose the bottom copper layer to the solution, subsequently; an oxidation current which attributed to the regeneration of the original cuprous oxide layer is used to reflect the concentration of these purine derivatives. In a 50mM phosphate buffer, pH 7.0, this approach provides a high sensitivity with LOQ of sub-micro molar level of five purines and high stability with a RSD of 2.5% for 10 μM xanthine (N=12). This method does not suffer from most biological species including ascorbic acid, acetaminophen, creatine, dopamine, sarcosine, ammonium ion, chloride ion, and urea at equal or higher than its physiological concentration.