Detection and Mapping of Cannabinoids in Single Hair Samples through Rapid Derivatization and Matrix-Assisted Laser Desorption Ionization Mass Spectrometry

The sample preparation method reported in this work has permitted for the first time the application of Matrix Assisted Laser Desorption Ionization Mass Spectrometry Profiling and Imaging (MALDI-MSP and MALDI-MSI) for the detection and mapping of cannabinoids in a single hair sample. MALDI-MSI analysis of hair samples has recently been suggested as an alternative technique to traditional methods of GC-MS and LC-MS due to simpler sample preparation, the ability to detect a narrower time frame of drug use and a reduction in sample amount required. However, despite cannabis being the most commonly used illicit drug worldwide, a MALDI-MS method for the detection and mapping of cannabinoids in a single hair has not been reported. This is probably due to the poor ionization efficiency of the drug and its metabolites and low concentration incorporated into hair. This research showed that the in situ derivatization of cannabinoids through addition of an N-methylpyridium group resulted in improved ionization 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-nor-delta(9)-carboxy-tetrahydrocannabinol glucuronide (THC-COO-glu). Additionally, for the first time an in-source re-arrangement of THC was observed and characterised in this paper thus contributing to new and accurate knowledge in the analysis of this drug by MALDI mass spectrometry.