Tetrahydrocannabinol (THC) is the principal psychoactive constituent of cannabis and one of at least 113 total cannabinoids identified in the plant. Cannabis is a controlled substance although medicinal use for treating pain, nausea, and other symptoms of chronic diseases such as multiple sclerosis has been legalized recently by several countries. Detection of THC and its metabolites such as delta-9-THC is typically done by urine or saliva analysis and confirmed by mass spectrometry.