Cannabis stable isotopes

Click on image to expand

In earlier work, we explored growth locations using DEA samples. We showed that hydrogen isotope analysis of cannabis (marijuana) recorded the cultivation location of plants, whether measured in the leaves or the flowers. This is because plants use the hydrogen atoms in local water when forming their hydrogen-containing molecules. This geographic signal remains intact after harvest, allowing reconstruction of the origins of marijuana sold on the streets. Today isoscapes have emerged as a powerful way to describe geographic patterns. We can construct cannabis isoscapes to predict the cultivation origins of specific plants or flowers. On the left we show the origins of marijuana sold across the USA  in 2010. 

Have these patterns changed now that medical and recreational cannabis (marijuana) are sold in nearly two dozen states across the USA? Stable isotope analysis is an analytical tool for regulators to ensure that cannabis is cultivated only in prescribed locations.

Carbon isotope analysis of cannabis (marijuana) distinguishes plants cultivated indoors from those cultivated outdoors. Our earlier research, based on DEA seizure records data, highlighted a distinct carbon isotope ratio difference between indoor- and outdoor-seized cannabis for both leaves and flowers. Our recent efforts have improved on the predictability and reliability of this analytical tool. Thus, regulators now have a reliable tool to verify that marijuana sold in a dispensary was indeed cultivated indoors as required by regulations. Other cannabis-isotope studies confirm distinct carbon isotope patterns associated with cultivation conditions.

Recent research by Brett Tipple in the Ehleringer Lab has shown that these carbon isotope differences between indoor versus outdoor cultivated plants also appear within specific compounds of cannabis.