Comparison of Bulk and Compound-Specific d13C Isotope Ratio Analyses for the Discrimination Between Cannabis Samples

Five marijuana samples were compared using bulk isotope analysis compound-specific isotope ratio analysis of the extracted cannabinoids. Owing to the age of our cannabis samples, four of the five samples were compared using the isotope ratios of cannabinol (CBN), a stable degradation product of ?9-tetrahydrocannabinol (THC). Bulk d13C isotope analysis discriminated between all five samples at the 95% confidence level. Compound-specific d13C isotope analysis could not distinguish between one pair of the five samples at the 95% confidence level. All the measured cannabinoids showed significant depletion in 13C relative to bulk isotope values; the isotope ratios for THC, CBN, and cannabidiol were on average 1.6 parts per thousand, 1.7 parts per thousand, and 2.2 parts per thousand more negative than the bulk values, respectively. A more detailed investigation needs to be conducted to assess the degree fractionation between the different cannabinoids, especially after aging.