Extended automation for on-line or off-line micro-SPE clean-up of QuEChERS extracts for GC-MS/MS analysis of pesticides residues in food

Importance of the topic

Pesticide residue analysis in food is essential for safeguarding consumer health, ensuring compliance with regulatory maximum residue levels (MRLs), and maintaining confidence in food supply chains. As demand rises for rapid throughput and reliable data in routine testing laboratories, efficient sample clean-up and automation become critical to reduce manual effort, minimize human error, and protect analytical systems from matrix-induced contamination.

Objectives and overview of the study

This work presents an automated workflow integrating QuEChERS extraction with a miniaturized solid-phase extraction (µ-SPE) clean-up, automated sample dilution, and calibration standard preparation. The aim was to validate this platform for GC-MS/MS analysis of 172 pesticides in five cereal matrices (barley, oat, rice, rye, and wheat), demonstrating compliance with SANTE guidelines and scalability for high-throughput laboratories.

Methodology

A 5 g cereal sample was extracted using citrate-buffered QuEChERS (EN 15662). Manual dispersive-SPE (d-SPE) clean-up was compared with automated µ-SPE cartridges containing PSA and MgSO₄ sorbents, operated on a TriPlus RSH autosampler. Automated steps included sample loading, sorbent interaction under controlled flow, elution of analytes, and subsequent dilution in ACN. A semi-procedural matrix-matched calibration was performed by spiking blank extracts prior to clean-up to correct for recovery losses.

Used instrumentation

• Thermo Scientific TriPlus RSH robotic autosampler equipped with µ-SPE, analyte protectant, and injection modules
• Thermo Scientific Exactive Orbitrap GC-MS
• Thermo Scientific XCalibur and TraceFinder 4.1 software for data acquisition, deconvolution, and unknown screening

Main results and discussion

The µ-SPE clean-up removed over 70% of matrix interferences compared to d-SPE, sharpening chromatographic profiles and protecting the system from co-extractives. Spiked recovery rates ranged from 70% to 120% with relative standard deviations below 20% across all pesticides. At low-level spikes (1 µg/kg), recoveries remained acceptable, with semi-procedural calibration effectively compensating for any losses. Automated dilution enabled up to eight calibration levels (1:5 to 1:10 000) in matrix, supporting quantitation from 1 to 100 µg/kg.

Benefits and practical applications of the method

• Unattended 24/7 operation reduces manual labor and human error
• High sample throughput: up to 54 samples overnight vs. none with manual handling
• Miniaturized sorbent reduces solvent use and waste
• Robust performance across diverse cereal matrices meeting regulatory criteria

Future trends and opportunities

Extending validation to more complex and high-fat matrices, customizing µ-SPE sorbent blends for diverse food commodities, and integrating on-line LC-MS/MS workflows will further advance automated pesticide testing. Development of real-time quality control and machine-learning–driven data evaluation may enhance method resilience and data interpretability.

Conclusion

The automated QuEChERS/µ-SPE workflow with integrated dilution and calibration demonstrates robust, high-throughput performance for pesticide residue analysis in cereals. It aligns with SANTE guidelines, minimizes manual operations, and delivers reliable, reproducible data while optimizing laboratory efficiency.

References

• S.J. Lehotay, L. Han, and Y. Sapozhnikova, Chromatographia, 79, 1113–1130 (2016)
• Elena Hakme and Mette Erecius Poulsen, Journal of Chromatography A, 1652 (2021), [462384]