Comprehensive Untargeted Screening & Quantitation of Pesticides in Cannabis Using GCxGCand High Performance Time-of-Flight Mass Spectrometry

Significance of the Topic

As the legal landscape for cannabis broadens, state agencies face challenges ensuring consumer safety by monitoring pesticide residues in complex plant matrices. Accurate quantitation and comprehensive screening are essential to guard public health and meet evolving regulatory demands.

Objectives and Study Overview

This study presents an integrated approach combining two-dimensional gas chromatography (GCxGC) with high-performance time-of-flight mass spectrometry for both targeted quantitation and untargeted detection of pesticides in cannabis-derived matrices, using CBD hemp as a proxy. Key goals included establishing method limits of quantitation, resolving matrix interferences, and identifying non-regulated contaminants.

Methodology

Sample preparation employed acetonitrile extraction followed by C18 solid phase cleanup, yielding a 25-fold diluted extract. Chromatographic separation utilized a thermal modulator coupled to a dual-column GCxGC system under a programmed temperature gradient, while comprehensive full-scan acquisition was performed at 250 spectra per second across m/z 45-520.

• Extraction: 1 g sample, 15 mL ACN, 5 min agitation
• SPE cleanup: Agilent SampliQ C18 cartridge with ACN rinses
• GCxGC conditions: Rxi-5MS primary column, Rtx-200 secondary, modulation period 3 s
• MS parameters: Ion source 250 °C, splitless injection, He carrier gas at 1.4 mL/min

Instrumentation

• LECO Pegasus BT 4D Time-of-Flight Mass Spectrometer
• LECO GCxGC Thermal Modulator with Agilent 7890 GC
• ChromaTOF software for hardware control, deconvolution, and non-target discovery

Results and Discussion

Method limits of quantitation for over 30 pesticides ranged from 50 to 200 ppb in sample extracts, meeting or exceeding California and Michigan regulatory thresholds. GCxGC provided enhanced chromatographic resolution, reducing coelution and improving spectral clarity. Non-target screening revealed unexpected chlordane degradation products and isomeric impurities not listed in standard certificates, demonstrating the value of untargeted analysis.

Benefits and Practical Applications

• High-resolution separation minimizes matrix interferences in complex cannabis samples
• Unified platform enables simultaneous targeted quantitation and discovery of unknown contaminants
• Robust method aligns with stringent regulatory requirements for product safety

Future Trends and Opportunities

As regulatory frameworks continue to diverge across jurisdictions, analytical methods must adapt to include emerging pesticides and degradants. Advances in GCxGC-TOFMS data processing and artificial intelligence-driven spectral interpretation will further enhance non-target screening capabilities.

Conclusion

The integration of GCxGC with high-performance time-of-flight mass spectrometry offers a powerful solution for comprehensive pesticide analysis in cannabis. By achieving low detection limits, clear separation, and non-target contaminant identification, this method supports laboratories in meeting evolving safety mandates and protecting consumer health.