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), energy-dispersive 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 time and the amount of nanocomposite controlling 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%

An ion-selective membrane electrode based on 4,13-didecyl-1,7,10,16-tetraoxa-4,13-diazacyclooctadecane (Kryptofix 22DD) incorporated into a polyvinyl chloride (PVC) membrane has been constructed. The electrode was prepared by a membrane containing dibutylphetalate (DBP) as plasticiser, Kryptofix 22DD as an ionophore, graphite powder as an additive and PVC as a matrix. Under the optimised membrane composition, the constructed electrochemical sensor shows the best response characteristics with a Nernstian behaviour over the concentration range of 1.0 × 10⁻⁴–1.0 × 10⁻¹ mol L⁻¹ of solution, with a detection limit of 1.20 × 10⁻⁵ mol L⁻¹. The electrode is applicable in the pH range of 1.5–4. It has a fast response time of about 10 s and can be used for at least 12 weeks without any considerable spellcheck in its potential response. The fabricated electrode reveals a good selectivity towards the ion in the presence of several cations in solution and also, it could be applied for determination of this ion in real samples.