Electrocatalytic determination of morphine at the surface of a carbon paste electrode spiked with a hydroquinone derivative and carbon nanotubes

This study aims at the electrochemical characterization of a novel sensor for the electrocatalytic determination of morphine (MO). The sensor is based on a carbon paste electrode spiked with 4-hydroxy-2-(triphenylphosphonio)phenolate (HTP) and multi-wall carbon nanotubes (HTP-MWCNT-CPE). The cyclic voltammetric responses of MO oxidation at the modified electrode surface at different potential scan rates show a characteristic shape typical of an EC catalytic mechanism. Cyclic voltammetry, chronoamperometry, and differential pulse voltammetry (DPV) were used to probe the characteristics of the modified electrode. The catalytic peak current obtained by DPV was linearly dependent on the MO concentration over the range 1.0–950.0 μM in two linear segments with a detection limit of 0.066 μM. The precision of DPV was found to be 3% for 15 replicate determinations of 4.0 μM of MO. For a binary mixture containing MO and acetaminophen (AC), two well-distinguished differential pulse voltammograms were obtained in the physiological pH (pH 7.0). The sensitivities of the modified electrode toward MO in the absence and presence of AC were found to be virtually the same, which refers to the fact that the electrocatalytic oxidation processes of MO are independent of AC. The modified electrode was successfully applied for the determination of MO and AC in a urine sample and pharmaceutical formulations.

► A hydroquinone derivative modified electrode is used for the electrocatalytic oxidation of morphine. ► The oxidation mechanism of morphine at the modified electrode surface is an EC catalytic mechanism. ► The detection limit of morphine determination at the modified electrode surface is obtained 0.066 μM. ► The modified electrode has been applied to the determination of morphine at a real sample. ► The modified electrode could separate the oxidation peak potentials of morphine and acetaminophen.