Subnanomolar detection of promethazine abuse using a gold nanoparticle-graphene nanoplatelet-modified electrode

A simple, sensitive, and effective adsorptive stripping voltammetric sensor for the detection of trace-level promethazine was created based on a gold nanoparticle-graphene nanoplatelet-modified glassy carbon electrode (AuNP-GrNP/GCE). AuNP-GrNP nanocomposites were synthesized using an electroless deposition process, and the morphology was characterized using UV-vis spectroscopy, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The electrochemical behavior and detection of promethazine at the AuNP-GrNP/GCE were investigated utilizing cyclic voltammetry and adsorptive stripping voltammetry. The AuNP-GrNP/GCE showed outstanding synergistic electrochemical activity for promethazine oxidation, a highly active surface area, great adsorptivity, and outstanding catalytic properties. The electrolyte pH, amount of AuNP-GrNP nanocomposite, preconcentration potential (vs. Ag/AgCl), and time were optimized to obtain a high performance electrochemical sensor. Under optimal conditions, the proposed sensor displayed two linear concentration ranges from 1.0 nmol L^-1 to 1.0 μmol L^-1 and from 1.0 to 10 μmol L^-1. The limits of detection and quantitation were 0.40 and 1.4 nmol L^-1, respectively. This sensor displayed high sensitivity, a capability for rapid analysis, and excellent repeatability and reproducibility. The developed sensor was effective and practical for promethazine detection in biological fluids and forensic samples, and the obtained results exhibited excellent agreement with the results obtained using the method described in the British Pharmacopoeia. Graphical abstract.