Pesticide Residue Analysis with Automated EDGE Extraction System and Multi-Layer GC/MS Sandwich Injection

Importance of the Topic

The demand for reliable and high-throughput pesticide residue analysis in food commodities is growing rapidly. Manual QuEChERS workflows, while effective, involve multiple steps that increase processing time, cost, and risk of human error. Automating sample preparation and calibration not only streamlines routine testing but also enhances reproducibility and laboratory efficiency.

Study Objectives and Overview

This study evaluates an automated solvent extraction system (EDGE) for the extraction of 235 pesticides from tomato samples, and demonstrates a novel multi-layer sandwich injection technique on a GC/MS platform for automated matrix-matched calibration. The goal was to compare performance metrics—including recovery, accuracy, and throughput—against the standard manual QuEChERS AOAC 2007.01 method.

Methodology and Instrumentation

Sample Extraction Workflows:

• Manual QuEChERS AOAC 2007.01: Salting‐out liquid–liquid extraction followed by dispersive solid-phase extraction (dSPE) on 15 g of tomato sample, using 15 mL acetonitrile without dilution.
• Automated EDGE Extraction: Solvent extraction on 10 g of tomato with 40 mL acetonitrile, yielding a 4-fold dilution and processing up to 12 samples per batch without user intervention.

Sandwich Injection for Calibration:

• 2-Layer Reversed Sandwich: Automated addition of internal standards (ISTD) and analyte protectants (AP) to samples.
• 3-Layer Sandwich: Preparation of matrix-matched calibration standards from concentrated solvent standards in a single injection.

Used Instrumentation

• EDGE Automated Solvent Extraction System (CEM Corporation)
• Agilent 7890B Gas Chromatograph coupled to 7010 Triple Quadrupole MS, operated in dynamic MRM, retention time locked with Agilent P&EP 4.0 Database
• Agilent GC Autosampler configured for 2- and 3-layer sandwich injections

Main Results and Discussion

Extraction Efficiency and Cleanup:

• Both EDGE and QuEChERS provided comparable pesticide recoveries with 96 % of compounds achieving 70–130 % at 10 ppb and 100 ppb spike levels.
• EDGE extracts exhibited lower total ion chromatogram (TIC) abundance at late retention times, attributed to four-fold dilution of matrix interferences.

Calibration Performance:

• Matrix-matched calibration via sandwich injection delivered linearity over 0.5–500 ppb (R2 > 0.99).
• Automated injection eliminated manual standard preparation, reducing potential for pipetting error.

Benefits and Practical Applications

• Significant reduction in hands-on time: 10 minutes per sample vs. >1 hour for manual QuEChERS.
• Minimized solvent consumption and waste through optimized extraction volumes.
• Consistent high recoveries across a broad pesticide panel support routine monitoring in food safety, QA/QC, and regulatory laboratories.

Future Trends and Opportunities

• Expansion of automated extraction techniques to diverse matrices such as grains, fruits, and beverages.
• Integration with high-resolution mass spectrometry and advanced data processing for non-targeted screening.
• Implementation of machine learning algorithms for adaptive method optimization and real-time quality control.

Conclusion

Automated EDGE solvent extraction combined with multi-layer sandwich injection on a triple quadrupole GC/MS offers a robust, efficient, and reproducible workflow for pesticide residue analysis. This approach matches or exceeds manual QuEChERS performance while significantly reducing manual labor and potential errors, making it an attractive solution for high-throughput food testing laboratories.

Reference

1. Agilent Pesticides and Environmental Pollutants Analyzer 4.0, Agilent Technologies, 5991-7418EN.
2. Westland J., Advantages of Reversed Sandwich Injection for Pesticide Residue Analysis, Agilent Technologies, Application Note 5991-7973EN, 2017.