Presumptive analysis of 4-methylmethcathinone (mephedrone) using Desorption Electrospray Ionisation - Mass Spectrometry (DESI-MS)

Abstract

4-Methylmethcathione (4-MMC or mephedrone) is a prevalent drug of abuse globally. 4-MMC is often marketed as ‘bath salts’ and is readily available over the internet. The need for a rapid universal technique capable of detecting an extensive range of drug compounds has become increasingly important with the continued emergence of novel drug analogues. Desorption electrospray ionisation - mass spectrometry (DESI-MS) is a mass spectrometry technique that allows for the analysis of compounds directly from ambient surfaces, reducing or eliminating the need for sample preparation. Although 4-MMC has gained significant attention in recent years, the application of the DESI-MS technique to the fast presumptive detection and chemical analysis of this analogue has not been presented. In the present study, DESI-MS was applied to the rapid qualitative analysis of 4-MMC. A particularly suitable surface, semi-porous polytetrafluoroethylene (PTFE, Teflon) was utilised, as it generated the least variable signal and reproducibility compared to other surfaces (polymethyl-methacrylate (PMMA) and polyvinyl chloride (PVC)). Selectivity of the technique to the detection of 4-MMC was evaluated by analysing a range of adulterated samples including mixtures containing caffeine, methylamphetamine, cathinone and paracetamol. Specificity based on tandem MS (MS/MS) was also demonstrated by analysing substances with the same molecular formula as 4-MMC. Accuracy (% RE) and precision (% RSD) of the method were found to be within 13% and 38%, respectively; and therefore the quantitative data provided by the DESI-MS method is limited compared to gas chromatography-mass spectrometry (GC-MS; accuracy < 13% and precision < 12%). The results suggest that DESI-MS can greatly aid in the rapid presumptive identification of 4-MMC and other similar novel drug analogues.