“Labs face increasing challenges in testing for cannabinoid intake as more states medicalize and legalize marijuana and as new and dangerous synthetic cannabinoids appear in the drug abuse market…the growing importance of oral fluid as a roadside test and the role of mass spectrometry (MS), presence of minor cannabinoids, and new breathalyzer technology in assessing an individual’s cannabis intake history.”
This is further discussed in “The New Era of Cannabis Testing” by Drs. Marilyn Huestis, Michael Smith covering complexities of roadside testing; emphsize need for results confirmation via mass spectrometry.