Flavin mononucleotide-exfoliated graphene flakes as electrodes for the electrochemical determination of uric acid in the presence of ascorbic acid

Abstract

Gold interdigitated microelectrodes (Au-IDA) modified with either graphene flakes exfoliated using flavin mononucleotide (FMN) (Gr-FMN) or graphene flakes and platinum nanoparticles (Pt-Gr-FMN) have been studied in the oxidation of uric acid (UA). An electrochemical method for the detection and quantification of UA in phosphate buffer solution at physiological pH (PBS, 0.25M, pH7) in the absence and presence of ascorbic acid (AA) has been studied by cyclic voltammetry. The quantification of UA was investigated by cyclic voltammetry, presenting an oxidation peak at 0.99V with both modified electrodes. Linearity range of 60–578μM and 60–345μM has been found for Gr-FMN/Au-IDA and Pt-Gr-FMN/Au-IDA electrodes, respectively. Limits of detection of 18μM were obtained for both electrodes, and the repeatability was studied at 177μM providing 4% and 8% for Gr-FMN/Au-IDA and Pt-Gr-FMN/Au-IDA, respectively. AA interference has been studied by cyclic voltammetry, showing two clearly separated oxidation peaks, at 0.99V for UA oxidation and at 0.74V for Gr-FMN/Au-IDA and 0.70V for Pt-Gr-FMN/Au-IDA for AA oxidation. Linearity range has been studied in presence of 250μM AA obtaining a working range of 60–578μM for Gr-FMN/Au-IDA electrode and of 60–288μM with Pt-Gr-FMN/Au-IDA electrode. Limits of detection remain at 18μM for both electrodes and the repeatability was studied at 177μM providing 8% and 14% for Gr-FMN/Au-IDA and Pt-Gr-FMN/Au-IDA electrodes respectively.