As the number of U.S. states allowing the adult use of cannabis and cannabis products increases, so does the need for product testing before retail sale. States that have legalized recreational use have specified testing requirements for pesticide residues in cannabis flower and cannabis products. Because the specific pesticides and action levels vary from state to state, a comprehensive approach to residue analysis can meet the requirements of multiple U.S. state regulations with a single analysis. The challenge of quantifying pesticide residues in cannabis is complex because of the high concentration of cannabinoids and terpenes relative to the levels of pesticides that may be present. Here we present a straightforward acetonitrile extraction using a solid-phase extraction (SPE) cartridge and targeted dispersive solid-phase extraction (dSPE) cleanup. The final dilute extract is analyzed with both gas chromatography–tandem mass spectrometry (GC–MS/MS) and liquid chromatography–tandem mass spectrometry (LC–MS/MS) for a comprehensive target list (200+ compounds) that encompasses those identified on individual U.S. state lists. Limits of quantitation meet or exceed individual U.S. state requirements.
The key to successful pesticide residue analysis in cannabis and cannabinoid products is understanding and gaining control of the background matrix. With a reduced matrix load in the final extract, GC issues like fouled or plugged syringes, dirty inlets or liners, and contaminated sources are greatly reduced. LC issues such as fouled or dirty valves, decreased column performance, contaminated spray shields and sources are less likely with the reduced matrix present in the sample extracts. With fewer potential interfering isobars, detector conditions are more stable and performance increases, resulting in increased sensitivity and stability in both baselines and compound response. All these factors combined provide a laboratory with increased sample throughput and a reduction in downtime because of maintenance and repairs. The use of high sensitivity MS/MS systems will allow laboratories to utilize calibration curves at sub-parts-per-billion levels.
By using a comprehensive approach to residues analysis, as is traditionally applied to conventional agricultural crops, a laboratory will be able to screen for the compounds required by regulation in addition to pesticides not included on a U.S. state list. There are many pesticides with similar chemistries and modes of action as those on a state specific list that could go undetected and enter the retail marketplace unless a more comprehensive approach is taken.
The authors would like to thank Melissa Churley with Agilent Technologies and Dr. Joan Stevens for their assistance with this work.
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Rick Jordan is the Laboratory Manager at Pacific Agricultural Laboratory in Sherwood, Oregon. Daniel Miller is the Technical Director at Pacific Agricultural Laboratory. Lilly Asanuma is a chemist at Pacific Agricultural Laboratory. Anthony Macherone is a Senior Scientist with Agilent Technologies and a visiting professor at The Johns Hopkins University School of Medicine. Direct correspondence to: [email protected]
How to Cite This Article
R. Jordan, L. Asanuma, D. Miller, and A. Macherone, Cannabis Science and Technology 1(2), 26-31 (2018).