Electrocatalytic oxidation and electrochemical detection of guanine, l-arginine and l-lysine at a copper nanoparticles-modified electrode

Abstract

The electrocatalytic oxidation of two amino acids, L-arginine and L-lysine, and the purine base guanine at a copper nanoparticles-modified carbon paste electrode (NCPE) was investigated. The results were also compared with a copper microparticles-modified carbon paste electrode (MCPE). In the voltammograms recorded using these electrodes, one anodic oxidation peak related to the electrocatalytic oxidation of the analytes (guanine, L-arginine and L-lysine) appeared through an electrocatalytic mechanism (an electrochemical reaction followed by a chemical reaction regenerating the initial redox species, EC′). For the electrooxidation of guanine, L-arginine and L-lysine, the catalytic rate constants were obtained as 5.5, 2.98 and 0.56 cm³ mol⁻¹ s⁻¹, respectively, the transfer coefficients were obtained as 0.59, 0.43 and 0.46, respectively, and the diffusion coefficients were obtained as 1.93, 1.54 and 3.28 × 10⁻⁶ cm² s⁻¹, respectively. These analytes were oxidized on NCPE with higher rates at low potentials compared to MCPE. This behavior was related to the nanosize effect of copper nanoparticles. Finally, a simple, sensitive and time-saving amperometric procedure was developed for the analysis of the analytes in both batch and flow systems. Using the amperometric procedure, guanine, L-arginine and L-lysine were quantified with linear ranges of 12.5–62.5, 20–263 and 50–1100 μM, respectively, calibration sensitivities of 5.8, 4.8 and 4.3 × 10⁻² μA M⁻¹, respectively, and limits of detection of 3.7, 4.3 and 8.6 μM, respectively, in batch system. In addition, for the flow system, guanine, L-arginine and L-lysine were quantified with linear ranges of 1–50, 50–700 and 100–1000 μM, respectively, calibration sensitivities of 4.4, 3.7 and 3.1 × 10⁻² μA M⁻¹, respectively, and limits of detection of 0.23, 20.0 and 29.1 μM, respectively.