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

Smith, JP, Metters, JP, Irving, C, Sutcliffe, OB and Banks, CE (2013) Forensic electrochemistry: the electroanalytical sensing of synthetic cathinone-derivatives and their accompanying adulterants in "legal high" products. ANALYST, 139. ISSN 0003-2654

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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), ( )-40-methylmethcathinone [3b, 4-MMC, ( )-mephedrone] and ( )-40-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 mg mL 1 for 3a (at pH 12) and 16–350 mg mL 1 for both 3b and 3c in pH 2, with limits of detection (3s) found to correspond to 44.5, 39.8 and 84.2 mg mL 1 respectively. Additionally adulterants that are commonly incorporated into cathinone legal highs are electrochemically explored at both pH 2 and 12.