A biopolymer-based voltammetric sensor for thymine: Elucidation of electrochemical kinetics

Abstract

In the work accounted here, the electro-oxidation of one of the pyrimidine bases thymine is studied on a glassy carbon electrode modified with the biopolymer, poly (l-glutamic acid), as the probe. On the probe, the overpotential for thymine oxidation in alkaline medium has been significantly decreased attesting the electrocatalytic nature of the biopolymer film. The experimental parameters to obtain the lowest oxidation potential have been optimised and the probe calibrated for the determination of thymine. In the square wave mode, using 0.1 M NaOH as the supporting electrolyte, the oxidation peak current was found to be linear in the range from 30 to 1000 μM, with a detection limit of 9.2 μM. The diffusion coefficient of thymine in 0.1 M sodium hydroxide has been determined using chronoamperometric studies. To study the mechanistic aspects of the electro-oxidation process, variation of the oxidation peak parameters with scan rate has been studied in the linear sweep mode. Electrochemical kinetic parameters, namely charge transfer coefficient α and the standard heterogeneous rate constant ks for the electro-oxidation, have also been determined. The determination of thymine in spiked synthetic blood serum and urine has been conducted to demonstrate the application of the sensor for thymine determination in real samples.