Novel Residue Analysis of Various Food Samples using GC- and GC×GC-HRMS with Encoded Frequent Pulsing™

Importance of the Topic

Environmental contaminants, including pesticide residues, present significant challenges in food safety analysis due to complex sample matrices and the need for trace-level detection. The combination of comprehensive two-dimensional gas chromatography (GC×GC) with a high-resolution time-of-flight mass spectrometer (HR-TOFMS) enhanced by Encoded Frequent Pulsing™ (EFP) technology addresses these challenges by boosting sensitivity, resolution, and identification confidence.

Objectives and Overview of the Study

• Establish baseline sensitivity of a prototype GC-HRT TOFMS with and without EFP.
• Evaluate performance on complex environmental and pesticide standards in food matrices.
• Demonstrate advantages of GC×GC separation for reducing matrix interferences.

Methodology and Instrumentation

A Folded Flight Path® high-resolution multi-reflecting TOFMS (Pegasus® GC-HRT) was coupled to a comprehensive two-dimensional gas chromatograph. Encoded Frequent Pulsing™ multiplexing increased duty cycle and acquisition rates up to 200 spectra/s while preserving sub-ppm mass accuracy and resolving power >25,000.

Used Instrumentation

• Comprehensive two-dimensional gas chromatograph
• Pegasus GC-HRT multi-reflecting TOFMS with Folded Flight Path®
• Encoded Frequent Pulsing™ module and real-time decoding software
• Standard autosampler for injection reproducibility

Key Experimental Steps

1. Injection of performance standards without EFP to define sensitivity baseline.
2. Repeated injections of octafluoronaphthalene (OFN) at descending concentrations (1, 0.10, 0.05 pg/µL) with EFP to calculate instrumental detection limits (IDLs).
3. Preparation of six calibration levels (0.5–20 ppb) containing 107 pesticides in an eggplant matrix.
4. Analysis by one-dimensional GC and GC×GC to compare separation performance.

Main Results and Discussion

Enabling EFP improved the IDL for OFN from 0.12 pg/µL (without EFP) to 0.04 pg/µL at 0.10 pg/µL injections and 0.02 pg/µL at 0.05 pg/µL. Calibration curves for 107 pesticides exhibited excellent linearity (R² > 0.99 for most compounds) across the 0.5–20 ppb range, with limits of detection predominantly below 1 ppb. GC×GC successfully resolved analytes such as α-BHC and tefluthrine from siloxane interferences and complex matrix peaks, demonstrating significant improvements in separation and identification.

Benefits and Practical Application

• Trace-level detection of pesticides and contaminants with sub-picogram sensitivity.
• High mass accuracy and resolution support reliable peak identification and retrospective data mining.
• Comprehensive two-dimensional separation minimizes matrix effects in food samples.
• EFP multiplexing maintains spectral quality at elevated duty cycles.

Future Trends and Potential Applications

• Integration of EFP-enabled HR-TOFMS in routine QA/QC laboratories for enhanced food safety monitoring.
• Development of automated data processing workflows for high-throughput screening.
• Application of EFP with alternative sample introduction techniques such as thermal desorption.
• Use of archived full-mass-range datasets for retrospective analysis of emerging pollutants.

Conclusion

The application of Encoded Frequent Pulsing in a GC×GC-HR-TOFMS platform delivers significant sensitivity gains without compromising spectral fidelity or mass accuracy. This approach offers a powerful, versatile solution for trace-level residue analysis in complex food matrices, with strong potential for routine implementation and retrospective studies of environmental contaminants.

References

1. Willis P. et al. High Resolution Multi-Reflecting TOFMS with Multiplexing by Encoded Frequent Pulsing. ASMS 2015 Proceedings, TOA am.