Determination of Pesticide and Mycotoxin Residues in Dried Cannabis Flower: LC-MS/MS and GC-MS/MS Methodology to Meet the Recommended AOAC Regulatory Requirements for US States and Canada

Significance of the Topic

Cannabis products are subject to diverse and evolving regulatory limits for pesticide and mycotoxin residues across US states and in Canada. The lack of harmonized tolerance levels requires analytical laboratories to adopt sensitive, robust, and multi-residue methods capable of meeting or exceeding AOAC Standard Method Performance Requirements (SMPRs).

Objectives and Study Overview

This study aimed to develop and validate a unified workflow for determination of over 100 regulated pesticides plus key mycotoxins in dried cannabis flower. The method was designed to satisfy the lowest action levels defined by any US state or Canada, targeting LOQs at half those levels per AOAC guidelines. A secondary goal was to integrate both LC-MS/MS and GC-MS/MS (APGC) analyses on the same tandem quadrupole platform for enhanced efficiency.

Methodology and Instruments

Sample Preparation:

• Weighed 0.5 g dried cannabis, extracted with 10 mL acetonitrile and stainless steel grinding balls.
• Cleanup for LC-MS/MS: pass-through SPE using Oasis PRiME HLB to remove >95% chlorophyll, fats, phospholipids, and ~50% cannabinoids.
• Cleanup for APGC-MS/MS: dispersive SPE with MgSO₄, PSA, C18, and GCB to eliminate resin and polar interferences.

Calibration and Fortification:

• Matrix-matched standards prepared over 0.001–2.0 ppm (LC) and 0.004–0.5 ppm (GC) accounting for dilution factors of 20× and 200×, respectively.
• Recovery assessed at four spiking levels (0.01–0.1 ppm) with six replicates each.

Instruments Used

• ACQUITY UPLC H-Class PLUS with XBridge BEH C18 XP column coupled to Waters Xevo TQ-XS for LC-MS/MS.
• Agilent 7890A GC with APGC source on Xevo TQ-XS for GC-MS/MS.
• MassLynx v4.2 for data acquisition and processing.

Main Results and Discussion

The SPE protocol yielded clean extracts with acceptable recovery (60–115%, RSD <20%) for 100 pesticides and four mycotoxins. APGC-MS/MS provided enhanced specificity for GC-amenable analytes. Two compounds showed degradation: thiophanate methyl converted to carbendazim, and resmethrin degraded to an uncharacterized product. Method detection limits met or exceeded AOAC SMPR targets for all regulated analytes.

Benefits and Practical Applications

This approach offers:

• A single mass spectrometer for both LC and GC analyses to reduce capital investment.
• Rapid, simple sample preparation workflows appropriate for high-throughput testing.
• Compliance with varying state and federal regulatory requirements in North America.

Future Trends and Applications

Further refinement may include expansion to emerging contaminants, automation of sample cleanup, and coupling with high-resolution mass spectrometry for non-target screening. Harmonization of global cannabis residue limits could drive demand for standardized multi-residue methods.

Conclusion

The described LC-MS/MS and APGC-MS/MS workflows deliver sensitive, robust, and efficient analysis of pesticides and mycotoxins in dried cannabis. Method performance meets AOAC SMPR guidelines, enabling reliable compliance testing across jurisdictions.

Reference

AOAC Standard Method Performance Requirements (SMPR®) 2019.003 for quantitation of pesticides in cannabis plant materials.