A polypyrrole/GO/ZnO nanocomposite modified pencil graphite electrode for the determination of andrographolide in aqueous samples

This paper presents a novel electrochemical sensor based on a pencil graphite electrode (PGE) modified with molecularly imprinted graphene oxide/zinc oxide nanocomposites for a sensitive detection of andrographolide. This is the first report of the novel method of electroanalytical determination of andrographolide through a modified PGE. The modified PGE was successfully fabricated and characterized. Then, quantitative analyses were performed by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The optimum conditions for this analysis were the supporting electrolyte containing 0.1 M KCl and 0.001 M K3Fe(CN)6, citrate buffer of pH 4, modulation amplitude of 50 mV, and scan rate of 10 mV/s. Under optimized parameters, a good linear response was obtained for andrographolide detection by DPV with a range of 50–145 µM and a detection limit of 42.6 µM. The relative standard deviation (R.S.D.) of the three measurements is 1.47%, which shows the excellent repeatability of the proposed method, while reproducibility analysis produced a R.S.D. value of 4.46%. The proposed technique with optimum conditions exhibited good selectivity towards the detection of andrographolide in the presence of ascorbic acid, uric acid, and cyclodextrin. This method was successfully applied to determine andrographolide in real water samples, and the results are comparable with the established method.