Rapid Determination of the ‘Legal Highs’ 4-MMC and 4-MEC by Spectroelectrochemistry: Simultaneous Cyclic Voltammetry and In Situ Surface-Enhanced Raman Spectroscopy

Abstract

The synthetic cathinones mephedrone (4-MMC) and 4-methylethcathinone (4-MEC) are two designer drugs that represent the rise and fall effect of this drug category within the stimulants market and are still available in several countries around the world. As a result, the qualitative and quantitative determination of ‘legal highs’, and their mixtures, are of great interest. This work explores for the first time the spectroelectrochemical response of these substances by coupling cyclic voltammetry (CV) with Raman spectroscopy in a portable instrument. It was found that the stimulants exhibit a voltammetric response on a gold screen-printed electrode while the surface is simultaneously electro-activated to achieve a periodic surface-enhanced Raman spectroscopy (SERS) substrate with high reproducibility. The proposed method enables a rapid and reliable determination in which both substances can be selectively analyzed through the oxidation waves of the molecules and the characteristic bands of the electrochemical SERS (EC-SERS) spectra. The feasibility and applicability of the method were assessed in simulated seized drug samples and spiked synthetic urine. This time-resolved spectroelectrochemical technique provides a cost-effective and user-friendly tool for onsite screening of synthetic stimulants in matrices with low concentration analytes for forensic applications.

Electrochemical detection of mephedrone using a graphene screen-printed electrode: a new sensitive and selective approach to identify synthetic cathinones in forensic analysis

“…S1 -ESI †). Although this electrochemical behavior is similar to those reported in previous papers for MEP oxidation 15,[22][23][24][25]27 or reduction, 26,28 these proposed methods have only explored one of the electrochemical processes for application in forensic analysis. The influence of pH on peak potentials of MEP redox processes at the SPE-GP was evaluated (Fig.…”

“…In this context, alternative screening methods have been proposed for MEP detection using techniques based on Raman spectroscopy 14 and voltammetry. 15 Electrochemical methods have been successfully applied to screening tests of many drugs in forensic analysis, as surveyed in recent reviews, 16–19 including some SCs 20–22 such as MEP 15,22–28 or its metabolites. 29…”

“…In this context, alternative screening methods have been proposed for MEP detection using techniques based on Raman spectroscopy 14 and voltammetry. 15 Electrochemical methods have been successfully applied to screening tests of many drugs in forensic analysis, as surveyed in recent reviews, [16][17][18][19] including some SCs [20][21][22] such as MEP 15,[22][23][24][25][26][27][28] or its metabolites. 29 Among these electroanalytical methods, electrochemical sensors based on screen-printed electrodes (SPE) have been widely used in recent years for the detection of different electroactive analytes.…”

“…SPEs have also been reported for the determination of several illicit drugs, [32][33][34][35][36] including some SCs, 20,21,37 with particular reference to MEP. 15,22,23,26 Although all these electrochemical methods have allowed fast and simple detection of MEP, they have been applied using only one of the electrochemical processes (oxidation or reduction) of SCs. Furthermore, these electrochemical sensors did not present (or were not tested for) selective and sensitive detection of MEP without the interference of adulterants and other drugs commonly found in seized forensic samples, or in the presence of other SCs.…”

Interpol Review of Drug Analysis 2019-2022

“…HS-SPME-IMS method for determination of ketamine and midazolam [ 808 ]; magnetic dispersive SPME coupled with GC-MS for simultaneous determination of tramadol and fluoxetine in water and biological samples [ 809 ]; ultrasound-assisted dispersive SPME technique for simultaneous preconcentration and determination of ultra-trace amount of carbamazepine and phenobarbital [ 810 ]; review focusing on the sensing of DFSA drugs (Rohypnol, flunitrazepam, GHB and ketamine) and potential limitations for real life implementations of the sensors [ 811 ]; optimization and validation of a dried blood spot microwave-assisted extraction LC-MS method for the determination of selected substances from the date-rape drugs group: ketamine, benzodiazepines and cocaine [ 812 ]; simultaneous voltammetric determination of noscapine and lorazepam [ 813 ]; 2022 CV with portable Raman spectroscopy for determination of mephedrone (4-MMC) and 4-methylethcathinone (4-MEC) [ 814 ]; ion-selective electrodes for cocaine, tropane, atropine, and scopolamine [ 815 ]; electrochemical sensor for the simultaneous detection of morphine and methadone [ 816 ]; HPLC method for simultaneous detection of four sedative-hypnotic drugs (diazepam, ketamine, nimetazepam, and xylazine) recovered from spiked beverages [ 817 ]; Vortex-assisted dispersive liquid-liquid microextraction-gas chromatography (VADLLME-GC) determination of residual ketamine, nimetazepam, and xylazine from drug-spiked beverages in liquid, droplet, and dry forms [ 818 ]; LC-MS-MS screening method for MA, AMP, MDMA, MDA, paramethoxymethamphetamine (PMMA), ephedrine, pseudoephedrine, ketamine, deschloroketamine (DCK), 2-fluorodeschloroketamine (2-F-DCK) and 2-oxo-PCE [ 819 ]; enrichment bag-based liquid-phase microextraction (EB-LPME) system to isolate and enrich AMP, MA, MDMA, ketamine, codeine and fentanyl from wastewater [ 820 ].…”