Kinetic and Thermodynamic Approach in the Development of a Voltammetric Sensor for Sunset Yellow

Abstract

An electrochemical sensor was developed for the determination of synthetic food color, sunset yellow (SY), based on the electrocatalytic properties of multiwalled carbon nanotube and gold nanoparticle (MWCNT/AuNP) composite. The glassy carbon electrode (GCE) modified with MWCNT/AuNP nanocomposite film exhibited excellent electron transfer ability toward the oxidation of SY with high sensitivity and stability. A pair of well defined quasi-reversible cyclic voltammetric peaks were observed with the formal potential (E0′ = −108 mV) vs. Ag/AgCl in phosphate buffer solution (PBS). Various kinetic and thermodynamic parameters of the redox reaction such as standard heterogeneous rate constant (ks = 7.944 × 10−1 s−1), electron transfer coefficient (α = 0.487), number of electrons (n = 1) exchanged and free energy of activation (ΔG) were calculated. Under optimum conditions, the nanocomposite film modified electrode showed a linear response in the range from 1 × 10−6 to 1 × 10−5 M, with a limit of detection 4.03 × 10−8 M. Analytical application of the developed sensor for quantitative determination of SY in commercially available soft drink samples were discussed.