Analysis of contaminants in hemp using LC and GC coupled to MS/MS

Importance of the Topic

Hemp is a low-THC variety of Cannabis sativa rich in CBD and CBG. Ensuring that hemp products are free from harmful pesticide residues and mycotoxins at parts-per-billion levels is critical for consumer safety and regulatory compliance.

Objectives and Study Overview

The primary goal was to establish a single-extract workflow combining LC-MS/MS and GC-MS/MS to detect a broad spectrum of pesticides and mycotoxins in hemp and cannabis plant material. The method targets strict minimum required performance levels (MRPLs) set by regulatory bodies.

Methodology and Instrumentation

Sample Preparation:

• Weigh 1 g of pulverized hemp and spike with isotopically labeled standards.
• Extract with 5 mL acetonitrile acidified with 1% acetic acid; vortex and centrifuge.
• Load 3 mL supernatant onto a 200 mg HLB SPE cartridge; elute and collect cleaned extract.
• Rinse cartridge with 300 µL methanol and combine eluates.
• Dilute for LC-MS/MS with methanol:acetonitrile:water (2:2:1, 1% acetic acid); inject 1.5 µL.
• For GC-MS/MS, perform dSPE cleanup with MgSO₄/C18, dilute with hexane:acetone (1:1, 1% acetic acid); inject 1 µL.

Used Instrumentation:

• LC-MS/MS: Shimadzu LCMS-8045 with Raptor ARC-18 column and ESI source.
• GC-MS/MS: Thermo Trace 1310 coupled to TSQ 8000, Rxi-5ms column, EI source.

Chromatographic Conditions:

• LC mobile phases: water and methanol with 2 mM ammonium formate and 0.1% formic acid; gradient from 5% to 100% B over 16.5 min.
• GC oven: 70°C to 315°C with stepped ramps; Helium carrier at 1.4 mL/min; splitless injection.

Main Results and Discussion

The workflow effectively removed hydrophobic interferences by diluting the extract with water prior to HLB cleanup and using methanol for elution. Calibration curves (0.005–1.5 µg/g) in hemp matrix showed R² > 0.99 for most analytes. LOQs were well below regulatory MRPLs (0.1 µg/g or lower). Accuracy ranged 70–130% and precision (RSD) was < 30% for the majority of targets.

Benefits and Practical Applications

The single-extract approach reduces solvent use and sample handling time while providing reliable quantification for QA/QC and regulatory testing of hemp and cannabis products. It supports state and international compliance, including California and Canada action levels.

Future Trends and Opportunities

Advances may include high-resolution mass spectrometry for non-target screening, automation of SPE workflows, miniaturized sample preparation, and expansion to emerging contaminants. Integration with real-time monitoring platforms could further enhance throughput and data quality.

Conclusion

A streamlined LC-MS/MS and GC-MS/MS workflow was developed for simultaneous analysis of pesticides and mycotoxins in hemp. The method meets stringent sensitivity, accuracy, and precision requirements, offering a robust solution for routine testing.

References

• Reyes-Garcés N, Myers C. J Sep Sci. 2021;44:2564–2576.