Forensic electrochemistry: the electroanalytical sensing of synthetic cathinone-derivatives and their accompanying adulterants in “legal high” products

Abstract

The production and abuse of new psychoactive substances, known as "legal highs" which mimic traditional drugs of abuse is becoming a global epidemic. Traditional analytical methodologies exist which can provide confirmatory analysis but there is a requirement for an on-the-spot analytical screening tool that could be used to determine whether a substance, or sample matrix contains such legal, or formally "legal highs". In this paper the electrochemical sensing of (±)-methcathinone and related compounds at a range of commercially available electrode substrates is explored. We demonstrate for the first time that this class of "legal highs" are electrochemically active providing a novel sensing protocol based upon their electrochemical oxidation. Screen-printed graphite sensing platforms are favoured due to their proven ability to be mass-produced providing large numbers of reliable and reproducible electrode sensing platforms that preclude the requirement of surface pre-treatment such as mechanical polishing as is the case in the use of solid/re-usable electrode substrates. Additionally they hold potential to be used on-site potentially being the basis of an on-site legal high screening device. Consequently the electroanalytical sensing of (±)-methcathinone (3a), (±)-4′-methylmethcathinone [3b, 4-MMC, (±)-mephedrone] and (±)-4′-methyl-N-ethylcathinone (3c, 4-MEC) is explored using screen-printed sensing platforms with the effect of pH explored upon the analytical response with their analytical efficiency evaluated towards the target legal highs. Interesting at pH values below 6 the voltammetric response quantitatively changes from that of an electrochemically irreversible response to that of a quasi-reversible signature which can be used analytically. It is demonstrated for the first time that the electroanalytical sensing of (±)-methcathinone (3a), (±)-mephedrone (3b) and 4-MEC (3c) are possible with accessible linear ranges found to correspond to 16–200 μg mL(−1) for 3a (at pH 12) and 16–350 μg mL(−1) for both 3b and 3c in pH 2, with limits of detection (3σ) found to correspond to 44.5, 39.8 and 84.2 μg mL(−1) respectively. Additionally adulterants that are commonly incorporated into cathinone legal highs are electrochemically explored at both pH 2 and 12.

Identification of new psychoactive substances (NPS) using handheld Raman spectroscopy employing both 785 and 1064 nm laser sources

“…According to the UNODC, gas chromatography -mass spectrometry (electron ionisation) (GC-MS (EI)) was the predominant analytical technique employed by EU countries for chemical analysis of NPS mixtures. [1] For example, this technique has been shown to successfully discriminate between NPS classes [14][15][16][17] as well as within classes such as cathinones, [18] aminoindanes [19,20] and benzylpiperazines. [21] In circumstances where no reference standards or data were available, nuclear magnetic resonance spectroscopy (NMR) has been used to determine the chemical connectivity of NPS such as cathinones [22] and aminoindanes.…”

“…[21] In circumstances where no reference standards or data were available, nuclear magnetic resonance spectroscopy (NMR) has been used to determine the chemical connectivity of NPS such as cathinones [22] and aminoindanes. [19,20] High performance liquid chromatography (HPLC) was used with various detectors to separate compounds between NPS classes [16] as well as within classes of cathinones [23] and cannabinoids. [24] In general, the techniques mentioned above require transport to a forensic laboratory and solvent dissolution/filtering before analysis.…”

An overview of recent developments in the analytical detection of new psychoactive substances (NPSs)

“…46 Solid synthetic cathinone samples (2-FMC, 2-MEC, 2-FEC and 2-EEC) were sampled directly without pre-treatment and positive ion mass spectra were acquired using a DART-SVP™ ion source interfaced to an AccuTOF mass spectrometer. 48,49 Smith et al 50,51 provided an alternative to chromatography and proposed a novel sensing protocol based upon the electrochemical methods. 47 The authors scope for this work is to provide a rapid screening method to quickly respond to the rapid evolution of designer drugs and the consequent testing backlogs that develop.…”

Forensic electrochemistry: indirect electrochemical sensing of the components of the new psychoactive substance “Synthacaine”

“…Previous work on the development of robust electrochemical methods for the sensing of the synthetic cathinones, either in their pure form 10 or in the presence of common adulterants 11 have the potential as rapid, simple and cost-effective † Electronic supplementary information (ESI) available. Previous work on the development of robust electrochemical methods for the sensing of the synthetic cathinones, either in their pure form 10 or in the presence of common adulterants 11 have the potential as rapid, simple and cost-effective † Electronic supplementary information (ESI) available.…”