Quantitation of Cannabinoids in Breath Samples Using a Novel Derivatization LC–MS/MS Assay with Ultra-High Sensitivity

As the legalization of medical and recreational marijuana use expands, measurement of tetrahydrocannabinol (THC) in human breath has become an area of interest. The presence and concentration of cannabinoids in breath have been shown to correlate with recent marijuana use and may be correlated with impairment. Given the low concentration of THC in human breath, sensitive analytical methods are required to further evaluate its utility and window of detection. This paper describes a novel derivatization method based on an azo coupling reaction that significantly increases the ionization efficiency of cannabinoids for LC-MS/MS analysis. This derivatization reaction allows for a direct derivatization reaction with neat samples and does not require further sample clean-up after derivatization, thus facilitating an easy and rapid "derivatize & shoot" sample preparation. The derivatization assay allowed for limits of quantitation (LOQ's) in the sub-pg/mL to pg/mL range for the five cannabinoids in breath samples, i.e., only 5~50 femtograms of an analyte was required for quantitation in a single analysis. This ultrahigh sensitivity allowed for the quantitation of cannabinoids in all breath samples collected within 3 hours of smoking cannabis (n = 180). A linear correlation between THC and cannabinol (CBN) in human breath was observed, supporting the hypothesis that CBN is converted from THC during the combustion of cannabis. The derivatization method was also applied to the analysis of cannabinoids in whole blood samples, achieving LOQ's at ten-pg/mL to sub-ng/mL level. This azo coupling-based derivatization approach provided the needed analytical sensitivity for the analysis of THC in human breath samples using LC-MS/MS and could be a valuable tool for the analysis of other aromatic compounds in the future.