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

Importance of the topic

The legal landscape for cannabis in the United States and Canada varies by jurisdiction, and each jurisdiction imposes its own limits on pesticide and mycotoxin residues. Reliable multi-residue analysis of both pesticide active ingredients and naturally occurring mycotoxins is essential to ensure consumer safety, meet regulatory requirements, and maintain product quality in medicinal and recreational cannabis markets.

Objectives and study overview

This application note describes the development and validation of a robust analytical workflow capable of measuring over one hundred pesticide residues plus key mycotoxins in dried cannabis flower. The method was designed to meet or exceed AOAC Standard Method Performance Requirements (SMPRs) that adopt the most stringent tolerance levels from any U.S. state or Canada. Dual chromatographic approaches—liquid chromatography-tandem mass spectrometry (LC-MS/MS) and atmospheric pressure gas chromatography-tandem mass spectrometry (APGC-MS/MS)—are employed to achieve the necessary sensitivity for different compound classes.

Methodology and Instrumentation

Sample preparation begins with grinding 0.5 g of dried cannabis in acetonitrile using a mechanical homogenizer. After centrifugation, the extract is split for two cleanup protocols:

• SPE pass-through using Oasis PRiME HLB cartridges for LC-MS/MS targets, removing approximately 95% of chlorophyll and lipids with minimal conditioning steps.
• Dispersive-SPE (dSPE) with MgSO₄, PSA, C18, and graphitized carbon black for APGC-MS/MS targets, achieving over 70% removal of cannabis resin and comparable decontamination of pigments and phospholipids.

Matrix-matched calibration curves were prepared in the range of 0.001–2.00 ppm (LC-MS/MS) and 0.004–0.500 ppm (APGC-MS/MS), accounting for method dilutions.

Instrumentation used

• Waters ACQUITY UPLC H-Class PLUS System
• XBridge BEH C18 XP Column (2.1×150 mm, 2.5 µm)
• Waters Xevo TQ-XS Tandem Quadrupole Mass Spectrometer with ESI source
• Atmospheric Pressure GC (APGC) source on the Xevo TQ-XS
• Agilent 7890A Gas Chromatograph for APGC–MS/MS
• MassLynx v4.2 Software for acquisition and processing

Key results and discussion

The SPE cleanup reduced cannabinoids by ~50% and eliminated most chlorophyll, fats, and phospholipids. The dSPE protocol removed more than 70% of resinous extractives but was avoided for LC-amenable analytes to prevent loss of acidic compounds such as daminozide. Most analytes achieved recoveries between 70% and 110% with relative standard deviations below 20% across spiking levels from 0.01 to 0.10 ppm. Method limits of quantitation (LOQs) ranged from 0.003 to 0.050 ppm, meeting or exceeding AOAC SMPR criteria. Two compounds—resmethrin and thiophanate methyl—showed degradation during extraction; thiophanate methyl was successfully monitored as its carbendazim degradant.

Benefits and practical applications of the method

• Comprehensive multi-residue coverage for regulated pesticides and mycotoxins in a single workflow.
• Use of the same tandem quadrupole mass spectrometer for both LC-MS/MS and APGC-MS/MS reduces capital equipment requirements.
• Rapid and simple sample preparation with minimal conditioning steps.
• High throughput suited for routine quality control in pharmaceutical, food safety, and regulatory testing laboratories.

Future trends and applications

As cannabis regulations continue to evolve, laboratories may expand target lists to include emerging pesticide chemistries and additional mycotoxins. Automation of sample preparation, integration with high-resolution mass spectrometry, and adoption of harmonized global tolerance standards will further enhance throughput and analytical confidence. Moreover, miniaturized and on-site testing platforms for rapid screening are likely to gain traction.

Conclusion

This validated dual-chromatography workflow delivers reliable quantitation of a broad range of pesticides and mycotoxins in dried cannabis. By leveraging SPE and dSPE cleanups followed by LC-MS/MS and APGC-MS/MS on a single Xevo TQ-XS instrument, the method meets stringent AOAC performance requirements and offers a practical solution for laboratories tasked with regulatory compliance and consumer safety assurance.

References

• AOAC SMPR 2019.003. Standard Method Performance Requirements for Quantitation of Cannabinoids in Plant Materials of Hemp (Low THC Varieties Cannabis sp.).