Preparation and characterization of a pencil graphite electrode modified with gold nanoparticles decorated poly (L-methionine) and its use in the simultaneous sensitive electrochemical analysis of ascorbic acid, acetaminophen, chlorpheniramine maleate, and caffeine

The current work outlines the use of an easy electrochemical sensor (AuNP-p(L-met)/PGE) based on pencil graphite electrode modified with gold nanoparticles-decorated poly(L-methionine) for the simultaneous anodic voltammetric analysis of four active drug substances, namely, ascorbic acid (A), acetaminophen (ACP), chlor-pheniramine maleate (CP) and caffeine (CF). The surface characterization of the sensor was carried out using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) Spectroscopy, Cyclic Voltammetry (CV), and Electrochemical Impedance Spectroscopy (EIS). The electrode fabrication conditions (scan rate and the number of cycles) and some experimental parameters (pH, methionine, and HAuCl4 concentrations) were optimized by using Differential Pulse Voltammetry (DPV), and the results showed that the determination of A, ACP, CP, and CF could be performed at the same potential window, with the oxidation peak potentials properly separated. Compared to bare PGE, AuNP/p(L-met)/PGE can significantly improve the electrocatalytic activity for the oxidation of A, ACP, CF, and especially CP with a remarkable increase in anodic peak currents, at an extent of 30.9%, 10.5%, 31.7%, and 663.8%, respectively. The sensor showed an excellent performance in the determi-nation of A, ACP, CP, and CF with a wide linear working range from 10 to 2000 mu M; 3.18-3000 mu M; 9.74-718 mu M and 8.3-2000 mu M; along with low detection limits of 3.03 mu M; 0.95 mu M; 2.92 mu M and 2.50 mu M, respectively. The method was successfully applied for the simultaneous quantification of A, ACP, CP, and CF at pharmaceutical dosages and in serum samples. The results obtained from pharmaceutical dosages were compared with those found by the HPLC method. The recovery and t-test results confirm the accuracy and precision of the developed AuNP-p(L-met)/PGE sensor, and no significant discrepancies were observed (95% confidence level).