Further research concerning the detection of oxidation products of THC-COOH following urinary adulteration
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In Australia and throughout the world, cannabis is one of the most widely used recreational substances. Whilst the recreational use of cannabis remains widely controversial, and the detection of its use in a range of biological matrices is of vital importance for drug testing laboratories and law enforcement agencies. The detection of drugs of abuse is critical in various areas, including pre-employment and post-incident drug screening, and sports drug testing. The use of cannabis by an individual may be ascertained by identifying the main metabolites of the major psychoactive constituent of cannabis, Δ⁹-tetrahydrocannabinol (THC), in biological matrices such as urine. The principal metabolite of THC is 11-nor-Δ⁹-tetrahydrocannabinol-9-carboxylic acid (THC-COOH), and may be detected in urine in both its free and glucuronide-bound form, with detection of either regarded as compelling evidence for the use of cannabis by an individual. Detection of THC-COOH by a range of instrumental techniques in drug testing laboratories is well established. However, this metabolite is known to be susceptible to reaction with certain adulterants. Adulteration of urine samples with oxidising adulterants has been shown to effectively mask cannabis use through reaction with THC-COOH. As such, the primary goals of this research are to assess the efficacy of a range of adulterants on the detection of THC-COOH in vitro, ascertain whether novel reaction products specific to the reaction of THC-COOH with selected adulterants form, and to assess the potential of these compounds to act as markers of both cannabis use and urine adulteration. Successful detection of a range of reaction products of THC-COOH was achieved, and three adulterants selected for further research: pyridinium chlorochromate, Betadine and bleach. Structural elucidation of these reaction products was attempted, and validated methods were developed for the quantitative detection of THC-COOH and qualitative detection of the targed reaction products following urine adulteration. Kinetics, pH and stability studies demonstrated that these reaction products formed under a range of pH and sample storage conditions, and critically, remained detectable for at least twenty days following adulteration. Detection of these potential markers of urine adulteration was also successfully achieved through the adulteration of authentic cannabis-positive urine specimens. This detection in authentic urine specimens is considered significant, as it highlights the potential for these novel compounds to be incorporated into current drug testing regimes employed by drug testing laboratories, and a potential means by which both cannabis use and urine adulteration may be conclusively identified.
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