Detection and Mapping of Cannabis Use in Hair Samples Using Mass Spectrometry

Abstract

Hair differs from other human materials used for toxicological analysis, such as blood or urine, because of its substantially longer window of detection (months to years) enabling retrospective investigations of drug consumption. Due to its solid and durable nature, hair may be analysed centuries after growth with little degradation. Other advantages of hair analysis include the non-invasiveness of its collection, which is of particular importance in infant/child investigations and the ease of sample storage. Although hair analysis offers the potential to reveal information which is not possible with other biological matrices, it also suffers from some unique limitations that can make interpretation of findings challenging. These are largely due to exposure of hair to the environment before analysis can take place. Current analytical techniques allow detection and quantification of cannabinoids in hair samples. Frequently used techniques include gas chromatography mass spectrometry and liquid chromatography mass spectrometry. The majority of studies exclusively analyse the natural products Δ9-tetrahydrocannabinol (THC), Cannabinol (CBN), cannabidiol (CBD) or the metabolite 11-nor-9-carboxy-tetrahydrocannabinol (THC-COOH). In this thesis THC, CBD, CBN, THC-COOH and the additional metabolite 11-Hydroxydelta-9-tetrahydrocannabinol (11-OH-THC) have been simultaneously detected and quantified in authentic hair samples using a novel atmospheric pressure chemical ionisation method coupled to gas chromatography mass spectrometry. The results of these findings are compared to self-report data and are largely found to be in concordance, with some anomalies. In addition, several strategies to overcome the complication of external contamination of hair samples were trialled and compared to self-report data. In this thesis there is also an investigation presented to demonstrate the in-situ derivatisation of cannabinoids using matrix-assisted laser desorption ionisation (MALDI). This is the first time a hair has been analysed for cannabinoids using MALDI and the first example of in situ derivatisation for hair samples. The addition of an N-methylpyridium group results in improved ionisation efficiency, permitting both detection and mapping of Δ9-tetrahydrocannabinol (THC), Cannabinol (CBN), cannabidiol (CBD) and the metabolites 11-nor-9-carboxy-tetrahydrocannabinol (THC-COOH), 11-Hydroxy-delta-9-tetrahydrocannabinol (11-OH-THC) and 11-nordelta(9)-carboxy-tetrahydrocannabinol glucuronide (THC-COO-gluc) in single hair samples. Additionally, for the first time an in-source rearrangement of THC is reported and characterised in this thesis, thus contributing new knowledge in the analysis of this drug by MALDI mass spectrometry.