Electroanalysis of amphetamine-type stimulants at nitrogen-doped carbon nanotube-modified electrodes

Abstract

This paper reports the utility of nitrogen-doped carbon nanotubes (N-CNT) and a chitosan biopolymer in the development of simple, cheap and rapid electroanalytical method for the detection of two important amphetamine-type stimulants, 3,4-methylenedioxyamphetamine (MDA), and 3,4-methylenedioxymethamphetamine (MDMA). The method used a screen-printed electrode (SPE) modified with the N-CNT/chitosan matrix, and its analytical performance was investigated by square wave voltammetry (SWV). The designed assay was short (<1 min per sample) and allowed the detection of MDA down to 0.22 μM with a linear range up to 50 μM (R² = 0.998) in a pH 10.0 phosphate buffer solution. The limit of detection for MDMA was 1.2 μM with a linear range up to 150 μM (R² = 0.992) in a pH 7.4 phosphate buffer. The spike-and-recovery experiments demonstrated accuracy of the method with good recovery of signal from MDA (93–99 %) and MDMA (82–94 %) in human urine and saliva. The proposed method required simple sensor preparation steps, used microliter-size (50 μL) sample volume and enabled the use of a single electrode for extended period (19 days) while retaining 94–96 % of the initial signal recorded from MDA and MDMA. The use of N-CNT/chitosan matrix for electrode modification offered a rapid method with a sensing platform that can potentially be integrated into portable devices for screening and analysis of the psychoactive stimulants in the biofluids.