Chapter 4 - Development of new electroanalytical method based on graphene oxide-modified glassy carbon electrode for mephedrone illicit drug determination

Abstract

Mephedrone (4-methylmethcathinone, or 4-MMC) is a new drug of abuse that has stimulant and euphoric effects similar to those of amphetamine, MDMA, and cocaine. The use of 4-MMC has been related to many deaths in Europe. Therefore, monitoring this drug in blood and in seized drugs is of paramount importance. Analytical methods based on chromatography have been widely used for the detection of 4-MMC. However, electrochemical methods are faster and easier to operate, making possible in situ analysis. Graphene oxide (GO) has been widely used in electrochemical sensors due to its high conductivity and superficial area. Therefore, this study reports the development of an analytical method based on the modification of a glassy carbon electrode (GCE) with graphene oxide (GO) and dihexadecyl hydrogen phosphate (DHP) for mephedrone determination. Firstly, GO was synthesized by Hummers’ method. The GO was characterized by FT-IR and Raman spectroscopy. The GO-DHP at 1mgmL−1 concentration was cast onto the surface of GCE by the drop-casting method. The functional groups on the GO surface play an important role in the performance of electrode in terms of sensitivity in the 4-MMC determination. By using differential pulse voltammetry (DPV) under optimized conditions (scan rate of 50mVs−1, pulse amplitude of 50mV, and pulse time of 50ms) and at pH6.0 in 0.1molL−1 phosphate buffer, a linear response range from 4.1 to 25.0μmolL−1 with a limit of detection (LOD) of 1.2μmolL−1 was obtained. The method precision was assessed in terms of interday (n=6) and intraday precision (n=2, consecutive days), in which relative standard deviations (RSD%) ranged from 0.28% to 8.26%. The developed method was not susceptible to interferences from benzocaine and caffeine and was applied in a synthetic sample, in which accuracy was attested by comparison with HPLC-DAD as reference technique.