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

Importance of the topic

Hemp, a Cannabis sativa variety low in THC and rich in CBD and CBG, can accumulate pesticides and mycotoxins that pose health risks. Analytical methods capable of detecting contaminants at parts-per-billion levels are essential to ensure product safety and regulatory compliance in both industrial and consumer applications.

Objectives and study overview

This work presents a streamlined workflow for simultaneous extraction and cleanup of hemp samples followed by analysis of a broad panel of pesticides and mycotoxins using LC-MS/MS and GC-MS/MS. The goal was to achieve low limits of quantification, high accuracy, and precision that meet or exceed state and country regulatory requirements.

Methodology and instrumentation

Sample preparation:

• Grind 1 g hemp; spike with isotopically labeled standards.
• Extract with 5 mL acetonitrile + 1 % acetic acid; vortex and centrifuge.
• Cleanup via HLB SPE cartridge with water pre-equilibration, vacuum elution, and methanol rinse.
• For GC: further clean extract using dSPE tubes containing MgSO₄ and C18; centrifuge.

LC-MS/MS analysis:

• Instrument: Shimadzu LCMS-8045 with ESI source.
• Column: Raptor ARC-18 (2.7 µm, 150 × 2.1 mm) with EXP guard.
• Mobile phases: water and methanol each containing 2 mM NH₄HCOO and 0.1 % formic acid; gradient over 19.6 min.
• Injection: 1.5 µL of sample diluted 1:1 with methanol:acetonitrile:water (1 % acetic acid).

GC-MS/MS analysis:

• Instrument: Thermo Trace 1310-TSQ 8000 with EI source.
• Column: Rxi-5ms, 30 m × 0.25 mm × 0.25 µm.
• Oven program: 70 °C to 220 °C at 30 °C/min, to 240 °C at 5 °C/min, to 315 °C at 10 °C/min.
• Injection: 1 µL splitless, inlet at 250 °C, carrier He at 1.4 mL/min.

Results and discussion

The method achieved LOQs well below 0.1 µg/g for most analytes, with calibration curves (0.005–1.5 µg/g) showing R² > 0.99 for almost all compounds. Accuracy ranged between 70–130% and precision (RSD) was under 30%. The water-methanol dilution and HLB cleanup effectively removed hydrophobic interferences common in hemp, and the MgSO₄ dSPE step eliminated residual moisture. A total of nine deuterated standards compensated for matrix and procedural variations.

Benefits and practical applications

• Single extraction covers both LC- and GC-amenable analytes.
• Rapid sample preparation with effective SPE and dSPE steps.
• Robust quantification meeting California and Canadian regulatory limits.
• Applicability to QA/QC laboratories, research, and industrial testing.

Future trends and potential applications

Advancements may include high-resolution MS for non-targeted screening, automated sample handling, miniaturized extraction devices, and online SPE-LC/MS workflows. Integration of machine learning for data processing and cloud-based monitoring could further enhance throughput and data reliability.

Conclusion

A comprehensive and efficient workflow was developed for the simultaneous analysis of a wide range of pesticides and mycotoxins in hemp. The method offers low detection limits, excellent accuracy, and precision, fulfilling stringent regulatory criteria and facilitating routine quality control.

References

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