A Sensitive and Robust Workflow to Measure Residual Pesticides and Mycotoxins from the Canadian Target List in Dry Cannabis Flower

Importance of the Topic

The legal requirement in Canada for rigorous testing of residual pesticides and mycotoxins in cannabis flower ensures consumer safety and compliance with strict reporting limits as low as 20 parts-per-billion. Developing a sensitive and robust analytical workflow is essential to accurately quantify a wide range of chemically diverse contaminants in a complex cannabis matrix.

Objectives and Overview of the Study

This application note describes a unified workflow to measure 96 pesticides and five mycotoxins mandated by Health Canada in dry cannabis flower. The study aims to achieve reliable limits of quantitation below regulatory thresholds by combining LC/MS/MS and GC/MS/MS techniques, while maintaining high throughput and instrument robustness.

Methodology and Sample Preparation

• Sample homogenization: One gram of dried cannabis flower is ground to a fine powder using ceramic or steel beads and vertical shaking.
• Extraction: Pesticides and mycotoxins are extracted with pesticide-grade acetonitrile.
• Cleanup: Extracts undergo solid-phase extraction on SampliQ C18 EC cartridges to remove lipophilic and polar interferences.
• Dilution: Final dilutions of 250× for LC/MS/MS and 125× for GC/MS/MS are applied with optimized solvent mixtures to match instrument requirements.

Used Instrumentation

• Agilent 1290 Infinity II UHPLC coupled to Agilent 6470 or Ultivo triple quadrupole LC/MS/MS with JetStream ESI source.
• Agilent 7890B GC system with 7010B triple quadrupole MS, featuring a multimode inlet, backflush capability, and HES source with JetClean.

Main Results and Discussion

• Recoveries and precision: Matrix-spike recoveries ranged from 70 % to 110 % with relative standard deviations typically below 5 %.
• Calibration performance: Linear calibration curves exhibited R² values ≥ 0.99 across 0.01–10 ppb (LC/MS/MS) and 1–50 ppb (GC/MS/MS) ranges.
• Limits of quantitation: LOQs in matrix were as low as 2.5 ppb for most pesticides by LC/MS/MS and 6–125 ppb by GC/MS/MS for nonpolar analytes.
• Instrument robustness: Optimized mobile phases, injection volumes, backflush strategies, and source cleaning routines maintained stable high-throughput performance.

Benefits and Practical Applications of the Method

The workflow provides a rapid return on investment by consolidating sample preparation and data processing for both chromatographic platforms. It enables licensed producers and testing laboratories to meet current Health Canada requirements and anticipate future regulatory tightening without extensive method redevelopment.

Future Trends and Opportunities for Use

• Expansion to additional pesticide and mycotoxin targets as regulatory lists grow.
• Automation of sample preparation to increase throughput and reduce operator variability.
• Integration of high-resolution mass spectrometry for confirmatory analysis and non-target screening.
• Adaptation of the workflow to other cannabis matrices such as oils, edibles, and extracts.

Conclusion

The combined use of acetonitrile extraction, C18 EC SPE cleanup, and multiplatform LC/MS/MS and GC/MS/MS analysis delivers a sensitive, robust, and scalable solution for comprehensive pesticide and mycotoxin testing in dry cannabis flower, fully compliant with strict Canadian regulations.

References

1. Pest Control Products Act, Government of Canada (2018), http://laws-lois.justice.gc.ca
2. Moulins J.R. et al., J. AOAC Int. 101 (2018) 56–68.
3. Kowalski J. et al., LC GC North America 35 (2017) 8–22.
4. Tuner C.E., Elsohly M.A., Boeren J., J. Nat. Prod. 43 (1980) 169–234.
5. Agilent Technologies Application Note 5991-9030EN (2019).