Improved Recoveries for GC/MS/MS Analysis of Pesticide Residues in Cannabis

Significance of the Topic

Rapid and reliable detection of pesticide residues in cannabis is critical for consumer safety and regulatory compliance. Complex plant matrices such as cannabis contain pigments, lipids and other interferents that can compromise sensitivity and accuracy in analytical workflows.

Objectives and Study Overview

This study evaluated an improved cleanup strategy for QuEChERS extraction of pesticides from dried cannabis. Two sorbent mixtures were compared: conventional PSA/C18/ENVI-Carb versus the novel Supel QuE Verde mix. The goal was to assess matrix removal, background reduction, recovery and reproducibility for a wide range of pesticides using GC/MS in full-scan mode and GC/MS/MS for quantitation.

Methodology

• Sample preparation: 1 g ground dried cannabis hydrated with water, extracted with 10 mL acetonitrile containing 1 % acetic acid in a citrate extraction tube.
• Cleanup: 1 mL supernatant processed in 2 mL tubes containing either PSA/C18/ENVI-Carb or Supel QuE Verde sorbents; samples shaken, centrifuged and aliquoted for analysis.
• Calibration: Multi-point, matrix-matched calibration curves at 50 ng/g in unspiked cannabis extract.

Instrumentation Used

• Gas chromatograph with SLB-5ms capillary column (30 m × 0.25 mm, 0.25 µm).
• Mass spectrometer: full-scan MS (m/z 45–500) for background evaluation; GC/MS/MS for quantitation.
• Oven program: 50 °C (2 min), ramp at 8 °C/min to 320 °C (5 min); injector at 250 °C, splitless; helium carrier gas at 1.4 mL/min.

Main Results and Discussion

Matrix removal visually showed that Supel QuE Verde effectively stripped green chlorophyll pigments, leaving a lighter, yellow-tinted extract and reducing GC background to the lowest total ion count. Recovery data (50 ng/g spike, n=3) indicated generally higher and more consistent recoveries for pyrethroid and triazole fungicides with Supel QuE Verde. Planar pesticides like quinoxyfen suffered poor recovery with conventional GCB but retained acceptable levels with the enhanced sorbent mix. Organophosphorus compounds displayed mixed performance but overall improved signal-to-noise. Reproducibility was robust (RSD <20 %) for most analytes; only tetramethrin and cypermethrin exceeded 20 % RSD after traditional cleanup.

Benefits and Practical Applications

• Enhanced matrix cleanup yields lower background and improved sensitivity in pesticide screening.
• Higher recoveries for a broad range of analytes, including challenging planar compounds.
• Reproducible results support routine QA/QC and regulatory testing in cannabis laboratories.

Future Trends and Applications

Ongoing development of sorbent materials promises further gains in selectivity and recovery. Integration of automated QuEChERS platforms and expansion to other complex botanical and food matrices will streamline multi-residue workflows. Advancements in high-resolution MS and data processing will enhance detection limits and compound identification.

Conclusion

The QuEChERS approach combined with Supel QuE Verde cleanup delivers a reliable, robust method for GC/MS(/MS) analysis of pesticides in cannabis. This protocol achieves effective pigment removal, reduced instrumental background, improved recoveries and consistent reproducibility, making it suitable for high-throughput testing and compliance laboratories.