The effect of modifying an edge-plane pyrolytic graphite electrode with single-wall carbon nanotubes on its use for sensing diclofenac

A simple and highly sensitive sensor based on edge-plane pyrolytic graphite electrode (EPPGE) coated with single-wall carbon nanotubes is proposed for diclofenac determination in nanomolar concentrations. The oxidation of diclofenac occurred in two well-defined peaks having peak potentials ∼439 and ∼854 mV at pH 7.2. The modified electrode showed excellent catalytic activity presenting much higher peak currents than those measured on a bare EPPGE. Under the optimum conditions, the calibration curve was linear in the concentration range 1 × 10⁻⁹-500 × 10⁻⁹ M and 25 × 10⁻⁹-1500 × 10⁻⁹ M for peaks I and II, respectively. The limit of detection for peaks I and II was found as 0.82 × 10⁻⁹ and 22.5 × 10⁻⁹ M, respectively. The developed sensor was applied for the determination of diclofenac in biological and pharmaceutical samples using square-wave voltammetry and the validation of results using high performance liquid chromatography showed excellent agreement.