Using Multi-walled Carbon Nanotubes Electrode as a Sensor for Voltammetric Determination of Thebaine

Thebaine or paramorphine (scheme 1) is an opiate alkaloid. A minor constituent of opium, thebaine is chemically similar to both morphine and codeine, but has stimulatory rather than depressant effects, causing strychnine-like convulsions at higher doses With the rise in the use of illegal drugs there is also an increased demand to identify illegal drug consumption. Consequently, forensic science laboratories must have specific and sensitive techniques to discriminate between the legal and illegal intake of opiates. Clinical and forensic testing of these compounds generally involve screening by immunological methods and confirmation using chromatographic techniques, usually of biological fluids, like blood and urine[1].Carbon nanotubes (CNTs) continue to receive remarkable attention in electrochemistry. Depending on their atomic structure, CNTs behave electrically as a metal or as a semiconductor. The subtle electronic properties suggest that CNTs have the ability to promote charge-transfer reactions when used as an electrode. The modification of electrode substrates with multi-walled carbon nanotubes (MCNTs) for use in analytical sensing has been documented to result in low detection limits, high sensitivities, reduction of overpotentials and resistance to surface fouling. MCNTs have been introduced as electrocatalysts and CNTs modified electrodes have been reported to give super performance in the study of a number of biological species, including cytochrome c, uric acid, NADH and quercetin. The electroactive sites of the MCNTs are edge plane-like sites/defects which can occur at the ends of the nanotubes or along the nanotube where tube compartments terminate [2-4].In this work, we studied the electrochemical behavior of thebaine on the multi-walled carbon nanotubes electrode and used this behavior as an electrochemical sensor for the determination of thebaine in human plasma and urine samples.