Modification of a pencil graphite electrode with multiwalled carbon nanotubes capped gold nanoparticles for electrochemical determination of Tramadol

Tramadol (TRA) is a narcotic-like pain reliever that is used for the treatment of moderate to severe pain. TRA like other narcotic drugs used as a pain treatment may be abused. The analgesic potency of tramadol is between weak opioid and morphine. In several controlled clinical studies, oral and parenteral tramadol effectively relieved moderate to severe postoperative pain associated with surgery. In addition, its overdose can cause dizziness, vomiting, and nausea since it is considered as a toxic material in nature [1]. Therefore, developing a sensitive and selective method for its determination in biological samples is very important. Several analytical techniques have been reported for the determination of tramadol, such as adsorptive stripping voltammetry, gas chromatography-tandem mass spectrometry [2], liquid chromatography [3], and ultraviolet spectrophotometry. Electrochemical methods, have attracted more attention in recent years for reasons of their recognition properties, simplicity, high sensitivity, good stability, high selectivity, low cost and fast response. In this research, we introduce a new electrochemical detection method for tramadol based on a pencil graphite electrode modified with multiwalled carbon nanotubes (MWCNT) and gold nanoparticles (AuNPs). The electrochemical sensor was fabricated via immersing of a pencil graphite electrode in multiwalled carbon nanotubes suspension and then deposition of the gold nanoparticles through electrochemical method. The fabrication process of the sensor was characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). Several significant parameters such as pH, scanning rate and the amount of carbon nanotubes controlling the performance of the sensor were examined and optimized. The influence of interfering species including ascorbic acid, uric acid and citric acid were evaluated and the results showed that the developed sensor has a high selectivity for tramadol. The proposed method shows requisite accuracy, precision, sensitivity and selectivity for determination of tramadol in tablet and biological fluids.