The application of stable ratio isotope mass spectrometry to illicit drug profiling
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The increase in appeal of IRMS for forensic investigations has been reflected in the number of forensic applications; which includes questioned documents, explosives and illicit drug profiling. Differences in isotopic abundances can be the result of variations in chemical processes and reaction conditions. The intelligence obtained through this analysis can be advantageous for law enforcement having both strategic and tactical value. In this study, stable isotope ratio analysis was used to measure the carbon, nitrogen and hydrogen of two illicit drug types, namely designer cathinones and ephedrine, and assessed for its provision for strategic and tactical intelligence. Following an observed increase in novel psychoactive compounds, IRMS was applied to the analysis of synthetic cathinones. Measurement of δ¹³C, δ¹⁵N and δ²H by EA/TC-IRMS showed sufficient variation allowing for the discrimination between samples. Variation in isotope profiles of the precursor material was the primary reason for differences with kinetic factors influencing the final isotope ratios, particularly where δ¹⁵N were concerned. IRMS was found to be useful when tactically comparing synthetic cathinones and discriminating between different synthetic batches. A novel method for the synthesis of ephedrine from N-methylalanine and benzaldehyde has received interest recently in peer-reviewed literature and online forums. Ephedrine synthesised from N-methylalanine was profiled using IRMS to develop its isotopic profile, thus furthering the capability of IRMS analysis currently employed at the NMI. δ¹³C of ephedrine was recorded between -29.7 and -38.4‰, with values depleted below -32‰ not previously recorded. δ²H fell between -39 and +335‰, primarily dependent on the source of benzaldehyde. The forensic intelligence obtained from the isotopic profile of ephedrine can be used both strategically and tactically, with the combination of a depleted δ¹³C and enriched δ2H unique to ephedrine synthesised from N-methylalanine. The δ¹⁵N, despite care taken to control conditions, fluctuated between synthetic batches and ranged from -24.3 and +10.1‰, proving to be useful in the tactical comparison of samples. These results satisfy the aims of the profiling and intelligence programs, providing an advantage to law enforcement as seizures manufactured via this route can be identified and monitored.
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