Detection, discrimination and quantification of amphetamine, cathinone and nor-ephedrine regioisomers using benchtop 1H and 19F NMR spectroscopy

Hulme, Matthew C, Hayatbakhsh, Armita, Brignall, Rachel M, Gilbert, Nicolas, Costello, Andrew, Schofield, Christopher J, Williamson, David C, Kemsley, E Kate, Sutcliffe, Oliver B and Mewis, Ryan E (2023) Detection, discrimination and quantification of amphetamine, cathinone and nor-ephedrine regioisomers using benchtop 1H and 19F NMR spectroscopy. Magnetic Resonance in Chemistry (MRC), 61 (2). pp. 73-82. ISSN 0749-1581

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Abstract

Amphetamine and cathinone derivatives are abused recreationally due to the sense of euphoria they provide to the user. Methodologies for the rapid detection of the drug derivative present in a seized sample, or an indication of the drug class, is beneficial to law-enforcement and healthcare providers. Identifying the drug class is prudent because derivatisation of these drugs, to produce regioisomers for example, occurs frequently to circumvent global and local drug laws. Thus, newly encountered derivatives might not be present in a spectral library. Employment of benchtop NMR could be used to provide rapid analysis of seized samples as well as identifying the class of drug present. Discrimination of individual amphetamine-, methcathinone-, N-ethylcathinone and nor-ephedrine-derived fluorinated and methylated regioisomers is achieved herein using qualitative automated 1H NMR analysis and compared to GC-MS data. Two seized drug samples, SS1 and SS2, were identified to contain 4-fluoroamphetamine by 1H NMR (match score median = 0.9933) and GC-MS (RRt = 5.42-5.43 min). The amount of 4-fluoroamphetamine present was 42.8 - 43.4% w/w and 48.7 - 49.2% w/w for SS1 and SS2 respectively from quantitative 19F NMR analysis, which is in agreement with the amount determined by GC-MS (39.9 - 41.4% w/w and 49.0 - 49.3% w/w). The total time for the qualitative 1H NMR and quantitative 19F NMR analysis is ca. 10 min. This contrasts to ca. 40 min for the GC-MS method. The NMR method also benefits from minimal sample preparation. Thus, benchtop NMR affords rapid, and discriminatory, analysis of the drug present in a seized sample.