This paper describes a simple method for determination of diclofenac using a gold electrode modified with functionalised multiwalled carbon nanotubes (f-MWCNTs)/graphene oxide (GO) nanocomposite film and gold nanoparticles (AuNPs). Electrochemical deposition method was employed for immobilisation of AuNPs at the surface of f-MWCNTs-GO nanocomposite film. The microscopic structure and morphology of the prepared films at the surface of the electrode were characterised by scanning electron microscopy (SEM), energydispersive X-ray spectroscopy (EDS) and electrochemical impedance spectroscopy (EIS). Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to study the electrochemical behaviour of diclofenac molecules. The effect of several parameters such as pH, electrodeposition timeand the amount of nanocompositecontrolling the performance of the sensor was examined and they were optimised. The proposed sensor showed an excellent catalytic activity towards the oxidation of diclofenac molecules. The oxidation peak current of diclofenac was linear in the concentration ranges of 0.4–80 µM and 100–1000 µM with a detection limit of 0.09 μM. The modified electrode was used for the quantitative determination of diclofenac in water, tablet and human urine samples where it gave recoveries ranging between 98.8% and 105%.

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