Deep into the Weeds – A Combined DART-HRMS and Chemometric Approach for Differentiating Hemp and Marijuana Varieties of Cannabis sativa

A challenging aspect of analyzing Cannabis evidence in a forensic laboratory is the differentiation of hemp and marijuana plant material, which are the two major varieties of Cannabis sativa. Although both varieties contain the psychoactive compound delta-9-tetrahydrocannabinol (THC), their content of this molecule differs. Federal law currently states that C. sativa that contains greater than 0.3 percent THC is the scheduled drug-type (marijuana), while plant material that contains less than 0.3 percent THC is the fiber-type (hemp). This definition imposes severe challenges on crime labs, including the increased workload that results from the need to analyze and quantify the THC content of all incoming C. sativa samples so that seized material can be appropriately designated. This NIJ-funded work sought to develop a direct analysis in real time – high-resolution mass spectrometry (DART-HRMS) and statistical analysis approach for the rapid differentiation of hemp and marijuana plant material to facilitate rapid analysis. Marijuana samples were obtained from DEA-registered suppliers, and hemp plant materials were purchased from licensed vendors. All samples were analyzed by DART-HRMS with no sample pretreatment. Exploratory statistical analysis of the small-molecule profiles revealed the potential for differentiating the two varieties by DART-HRMS. The results prompted the application of advanced statistical processing to the data, which revealed diagnostic m/z values for distinguishing between hemp and marijuana with a high level of certainty. The identities of several m/z values have been confirmed, with many being known cannabinoids or fragments of major cannabinoids and terpenes, resulting from analysis under ambient conditions. This combined DART-HRMS and chemometric approach to differentiate hemp and marijuana plant material would significantly aid in the interrogation and triage of C. sativa plant material prior to launching confirmatory techniques.