Using isotopic fractionation to link precursor to product in the synthesis of diphenidine hydrochloride: a tool for combating new psychoactive substances (NPSs)

Owen, Faye Hannah (2017) Using isotopic fractionation to link precursor to product in the synthesis of diphenidine hydrochloride: a tool for combating new psychoactive substances (NPSs). Masters by Research thesis (MSc), Manchester Metropolitan University.

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Abstract

In recent years, there has been an unprecedented growth in the emergence of “legal highs”, or as they are now commonly known, New Psychoactive Substances (NPS). In most cases, they mimic the effects of illicit substances, however, they circumvent legislation through changes in their chemical structures. NPS are being successfully sold through online venders under the titles “bath salts” and “research chemicals” and along with their low cost, are becoming an increasingly popular, convenient, alternative to controlled substances. Diphenidine, is an example of a fourth generation NPS that has increased in popularity as a recreational dissociative drug since its appearance in 2013. Diphenidine poses a threat to public health and safety due to lack of legislative control but also through the lack of literature concerning its toxicity, chemical and physical data, with evidence showing diphenidine has attributed to several deaths already. It is becoming apparent that there is a need for a rapid and selective detection method in order to identify and control not only diphenidine, but other legal and illicit substances too. Isotopic Ratio Mass Spectrometry (IRMS) is an analytical technique that has flourished within the forensic community, having the potential to not only link diphenidine samples of the same manufacturer, but also differentiate between sample seizures. IRMS looks beyond chemical composition but instead, at the relative isotopic abundances of the elements composing the starting materials and final product. Trace impurities could be used as a method of source identification, as the impurity will be unique to the drug and its history of origin. This could potentially allow discrimination between synthetic routes used. The main objective of the study is to determine whether IRMS can be used as tool to link product to precursor in the case of diphenidine hydrochloride, which if successful, would could have a wide variety of forensic applications for further NPS and illicit drugs. After designing and implementing a new GC-MS method to determine the purity of diphenidine hydrochloride, whilst considering peak area normalisation calculations and percentage yield data, the optimum method for the synthesis of diphenidine hydrochloride is F. This method uses 30 mmol piperidine and 1 hour stirring time under an inert atmosphere to yield diphenidine hydrochloride in much quantities with minimal trace impurities compared to the other methods employed. From IRMS data it is possible to distinguish between sources of precursors except when two sources are owned by the same brand, i.e. Sigma Aldrich can be distinguished from Alfa or Acros, but Alfa and Acros products cannot be discriminated. There are also significant changes the isotopic rations for both carbon and nitrogen when the physical parameters for the synthesis are changed, notably when the reaction is performed under argon and the wen the molar equivalents of the precursors are increased, i.e. the mmol ration of piperidine/ Like the source differentiation results, there are substantial different between 10 mmol and 20 mmol ratios, but it is difficult to distinguish between 20 mmol and 30 mmol. In conclusion, it would be possible to link precursor to product and also the synthetic pathway used, but not with 100% certainty.