Electrochemical studies of determination of C.I. Direct Red 80 based on a gold nanoparticles-modified carbon paste electrode

In this paper, a simple, convenient and sensitive electrochemical method has been developed for the determination of C.I. Direct Red 80. A gold nanoparticle modified carbon paste electrode was fabricated and used for study and sensitive determination of Direct Red 80 by cyclic voltammetry and differential pulse voltammetry. The overall analysis involved a two-step procedure: an accumulation step under open-circuit conditions, followed by voltammetric measurements of Direct Red 80 in a 0.1?M phosphate buffer solution at pH?=?3.0. The experimental conditions, such as the medium, pH and accumulation time, were optimised. The oxidation peak current was proportional to the concentration of Direct Red 80 from 5.0?×?10^?8 to 5.0?×?10^?7?M and 5.0?×?10^?7 to 3.0?×?10^?6?M, and the detection limit was 1.15?×?10^?8?M (S/N?=?3). The proposed method was used to detect Direct Red 80 in natural water and sewage with good accuracy.