Summary
Cannabis (marijuana) has been legalized for recreational and/or medical use by 23 states, the District of Columbia, and the territory of Guam. Thus, regulations regarding its production have become a topic of interest. The use of pesticides on cannabis is currently not regulated by the US EPA due to its listing as a Schedule 1 narcotic by the federal government. States that allow cannabis use for recreational and/or medical use have differing regulations regarding pesticides. As indicated in Table 1, the scope of regulation varies widely; from regulations on use, testing, and labeling, to no regulation at all.¹
Table 1. US State Regulations Regarding Pesticide Use and Testing for CannabisThere are no official test methods for the determination of pesticide residues in cannabis. However, a potential approach is the use of the “quick, easy, cheap, effective, rugged and safe” (QuEChERS) method outlined in AOAC official method 2007.01. In this application, QuEChERS was used in the extraction of pesticides from dried cannabis. The pesticides studied were selected from lists currently tested by several commercial cannabis testing laboratories. The list included triazole fungicides as well as organophosphorus, organochlorine, and pyrethroid insecticides. Also included was piperonyl butoxide, a pesticide synergist included on the state of Colorado’s list of “pesticides for use in marijuana production.” ² For cleanup of the extracts, two different sorbent mixes were evaluated: (1) PSA/C18/ENVI-Carb™ and (2) Supel™ QuE Verde. The first represents a conventional mix often described as “PSA/C18/ GCB” in QuEChERS protocols. PSA removes acidic interferences, while C18 retains hydrophobic interferences. Graphitized carbon blank (GCB or ENVI-Carb in this application) will retain chlorophyll and other colored compounds. However, while effective in removing pigment, GCB also retains target compounds with planar structures. Thus, pesticides with planar structures can be retained, reducing their recoveries. The second sorbent, Supel QuE Verde, contains a mixture of PSA, Z-Sep+ and an improved GCB. Z-Sep+ is a silica that is functionalized with both zirconia and C18. Zirconia will retain some fats and carotenoids, while C18 retains hydrophobic interferences. The improved GCB used in the Supel QuE Verde mix has been optimized to balance chlorophyll removal and improved recoveries of planar pesticides. When used to clean samples containing chlorophyll, this sorbent blend will provide better recovery of planar pesticides than sorbents containing traditional GCB.
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