Method Development in the Quantitative and Qualitative Analysis of Pseudoephedrine and Ephedrine and their Associated By-products, in the Manufacture of Methamphetamine

Abstract

(Pseudo)ephedrine is a significant problem in society due to its use as a precursor in the synthesis of methamphetamine. Large quantities are seized every year in New Zealand, and improved analytical techniques are needed at The Institute of Environmental Science and Research (ESR). Both quantitative and qualitative analysis were investigated. The study aimed to produce a validated quantitative method to determine the purities of (pseudo)ephedrine powders by high pressure liquid chromatography (HPLC). The validated method showed good accuracy, precision, and linearity for control powders at purities of 10.16% to 99.9% of the base form. Good selectivity with baseline separation was achieved between pseudoephedrine and ephedrine, and from other commonly observed interferences. A preliminary validation investigating the quantitative abilities of the SpinsolveTM benchtop nuclear magnetic resonance instrument yielded good precision, and linearity for pseudoephedrine hydrochloride control powders at purities of 10.16% to 81.08% of the base form. The method produced good accuracy at purities higher than 48.81% (concentration of 24.52 mg/mL). Poor selectivity was also observed. However, the method was cheap to run, and fast to prepare, showing several advantages over the analysis of samples by HPLC. Qualitatively, this research aimed to produce individual standards of the cis- and trans-1,2-dimethyl-3-phenylaziridine (aziridine), for use in casework. Their synthesis was achieved from the synthesis of (+)- and (-)-chloroephedrine from (+)-pseudoephedrine, followed by conversion to the aziridines in a basic solution. It has been observed that signals of TFA pseudoephedrine and ephedrine derivatives were produced following TFA derivatisation of samples that contain aziridines. This experiment confirms this problem by TFA derivatisation of the above cis- and trans-aziridine standards. Therefore, care needs to be taken when interpreting results of samples containing aziridines. Finally, the unexpected appearance of methcathinone in methamphetamine clandestine lab samples was investigated. Attempts to synthesise methcathinone from pseudoephedrine, by isolating suspected reagents (hydrogen peroxide, iron powder, iodine, and acid) and using conditions present in methamphetamine manufacture show low levels of methcathinone appearance in a variety of conditions. Thus, its appearance is believed to be insignificant.