Quantitation and Non-Target Detection of Pesticides in Spinach Extract with Pegasus BT 4D

Importance of the Topic

Accurate quantitation and identification of pesticide residues in complex food matrices are essential for consumer safety and regulatory compliance. Traditional one-dimensional GC methods often suffer from coeluting matrix interferences that limit sensitivity and reliability. Two-dimensional GC (GCxGC) coupled with high-speed TOFMS offers enhanced separation power and cryo-focusing effects that address these challenges.

Objectives and Study Overview

This application note examines the use of the LECO Pegasus BT 4D GCxGC-TOFMS system for quantitative and non-targeted detection of chlorinated pesticides in spinach extract. The goals were to demonstrate improved limits of detection (LODs), better calibration linearity, and the ability to uncover incurred or unexpected contaminants.

Methodology and Used Instrumentation

• Sample Preparation: Spinach was extracted using a QuEChERS protocol with dSPE cleanup. Matrix-matched standards were spiked with a chlorinated pesticide mix to avoid background bias.
• Chromatography: LECO GCxGC Quad Jet Thermal Modulator with Rxi-5ms (30 m × 0.25 mm × 0.25 µm) primary column and Rtx-200 (1 m × 0.25 mm × 0.25 µm) secondary column. Temperature program from 75 °C to 320 °C with 2 s modulation periods.
• Mass Spectrometry: Pegasus BT 4D TOFMS, ion source at 250 °C, mass range 45–570 m/z, acquisition rate 280 spectra/s for GCxGC.
• Data Processing: ChromaTOF software with Target Analyte Find (TAF) for quantitation and Non-Target Deconvolution (NTD) for screening, applying SANTE/11813/2017 criteria for unit mass resolution TOFMS.

Main Results and Discussion

• GCxGC separation significantly reduced matrix interference and improved peak resolution compared to 1D GC.
• Limits of detection decreased by up to tenfold (e.g., chloroneb from 5.0 to 0.5 ng/g) and calibration curves exhibited excellent linearity (R² > 0.9996).
• Non-target screening revealed additional incurred pesticides and a likely plasticizer. Chlorantraniliprole was detected only in the GCxGC data due to separation from a coeluting matrix peak.
• Comprehensive NTD deconvolution improved spectral clarity by isolating analyte signals from column bleed and coeluting components.

Benefits and Practical Applications of the Method

The combination of GCxGC and Pegasus BT 4D TOFMS provides enhanced sensitivity, selectivity, and confidence in both targeted quantitation and non-targeted screening. This approach supports stringent regulatory requirements and reduces false negatives in complex food analyses.

Future Trends and Applications

• Integration with high-resolution accurate mass detectors to further improve selectivity and mass accuracy.
• Automation of sample preparation and data processing for high-throughput pesticide screening.
• Application to a broader range of food and environmental matrices under evolving regulatory limits.
• Development of machine learning-driven deconvolution and library matching for rapid non-target identification.

Conclusion

GCxGC combined with the LECO Pegasus BT 4D TOFMS meets and exceeds SANTE/11813/2017 requirements, delivering superior separation, sensitivity, and robust detection of both target and non-target pesticides in spinach extract. This methodology is well suited for routine QA/QC, research, and regulatory laboratories facing complex sample challenges.

References

1. European Commission. SANTE/11813/2017 Guidelines on Analytical Quality Control and Method Validation for Pesticide Residues Analysis in Food and Feed.
2. LECO Corporation. Pegasus BT 4D GC×GC-TOFMS Application Note, Form No. 203-821-560, September 2019.