Analysis of Residual Pesticides and Mycotoxins in Cannabis Using UPLC-MS/MS and GC-MS/MS to Meet California Regulatory Requirements

Importance of the Topic

Increasing legal acceptance of cannabis has heightened the need for rigorous safety testing. Residual pesticides and mycotoxins must be quantified at low concentrations to protect consumer health and comply with California regulations.

Study Objectives and Overview

This study demonstrates a streamlined workflow combining simple acetonitrile extraction, dispersive SPE cleanup, and tandem LC-MS/MS and GC-MS/MS analysis to monitor 66 pesticides and 5 mycotoxins in cannabis flower. It leverages automated method generation from the Quanpedia database to satisfy California’s action limits (0.01–1 µg/g).

Methodology and Sample Preparation

• Sample preparation: 0.5 g ground cannabis spiked with target analytes, extracted in acetonitrile, homogenized, and centrifuged.
• Cleanup: dSPE with MgSO₄, PSA, C18, and GCB followed by centrifugation.
• Calibration: Matrix-matched curves spiked at 0.025–0.50 µg/g for LC and 0.025–1 µg/g for GC.

Used Instrumentation

• ACQUITY UPLC H-Class with Xevo TQ-S micro MS for LC-MS/MS.
• Xevo TQ-GC MS/MS with Rxi-5MS column for GC-MS/MS.
• MassLynx, TargetLynx, and Quanpedia software for acquisition, processing, and automated method setup.

Key Results and Discussion

• LC-MS/MS covered 62 pesticides and 5 mycotoxins in a single run; linearity (R²>0.99) down to 25 ppb for pesticides and 5 ppb for mycotoxins.
• GC-MS/MS covered 54 additional pesticides requiring EI; linear from 25 to 1000 ppb (R²>0.995).
• All action limits for California regulations were met or exceeded, with method sensitivities at low ng/g levels.
• Reproducibility: 50 consecutive GC injections at 0.1 µg/g showed <15% RSD.
• Recoveries: 80–120% for most analytes; some sorbent-affected compounds showed lower recoveries.
• Chromatographic resolution addressed co-elution challenges such as spinosad D vs. spinetoram J.

Benefits and Practical Applications

• Rapid, minimal prep workflow (<20 min LC, ~17 min GC) increases throughput.
• Automated method creation reduces development time and potential errors.
• Simultaneous multi-residue screening enhances laboratory efficiency and compliance.

Future Trends and Applications

Advances may include expanded automated databases for emerging contaminants, integration of high-resolution MS for non-target screening, and adaptation to other complex botanical matrices. Enhanced software workflows will further streamline compliance testing.

Conclusion

This integrated LC-MS/MS and GC-MS/MS workflow with simple dSPE cleanup offers robust, sensitive, and efficient multi-residue testing for California-regulated pesticides and mycotoxins in cannabis, ensuring reliable results at ppb-level action limits while minimizing method development effort.

References

• Legality of cannabis by U.S. jurisdiction, Wikipedia, 2018.
• California Department of Pesticide Regulation: Cannabis guidelines, 2018.
• Bureau of Medical Cannabis Regulation, California, 2018.
• Tran K. et al., Determination of Oregon pesticide list in cannabis, Waters application note, 2018.