Quantitative Analysis of Pesticides in QuEChERs Extracts Using APGC/MS/MS

Significance of the Topic

Pesticide residues in fruits and vegetables are subject to stringent regulatory limits worldwide. Ensuring accurate, sensitive, and high-throughput detection of multiple pesticides in a single analysis is critical for food safety and regulatory compliance. Advances in ionization technologies can enhance detection capabilities for a broad range of analytes in complex matrices.

Objectives and Study Overview

This study demonstrates the application of Atmospheric Pressure Gas Chromatography tandem mass spectrometry (APGC/MS/MS) for the quantitative analysis of GC-amenable pesticides in QuEChERS extracts of strawberry, pear, tomato, and spinach. The goals were to establish limits of detection (LOD), assess linearity, and evaluate method robustness across diverse matrices.

Methodology

• Sample Preparation: DisQuE QuEChERS extraction protocol in acetonitrile was applied to homogenized fruit and vegetable samples to obtain clean matrix extracts.
• Calibration Strategy: Nine-point matrix-matched calibration from 0 to 50 ng/mL using mixed pesticide standards; chrysene-d12 served as an internal injection standard at 2 ng/mL.
• Analysis Conditions: Injection into a 7890A GC coupled to Waters Xevo TQ-S equipped with an interchangeable APGC source; two MRM transitions monitored per analyte (quantifier and qualifier).
• Ionization Approach: APGC operated under wet and dry conditions to favor proton transfer or charge transfer, producing intense [M+H]+ ions with minimal fragmentation.

Used Instrumentation

• Waters Xevo TQ-S triple quadrupole mass spectrometer
• Atmospheric Pressure Gas Chromatography (APGC) source
• Agilent 7890A gas chromatograph

Main Results and Discussion

APGC/MS/MS delivered superior sensitivity and selectivity compared to traditional EI-GC/MS, yielding strong molecular ion signals and low background noise. Key findings include:

• Limits of detection ranging from 0.01 to 0.5 ng/mL for 20 target pesticides.
• Excellent linearity (R2 > 0.99) over 0.05–50 ng/mL across all analytes.
• Minimal matrix effects and consistent retention times, peak shapes, and responses among strawberry, pear, tomato, and spinach extracts.
• Representative chromatograms for heptachlor epox B at 1 ng/mL confirm reliable quantification in solvent and matrix at trace levels.

Benefits and Practical Applications

The APGC/MS/MS approach offers multiple advantages for routine pesticide residue analysis:

• Soft ionization reduces in-source fragmentation, enabling selective MRM transitions and improved sensitivity.
• Interchangeable APGC and ESI sources on a single MS platform facilitate both GC- and LC-amenable pesticide workflows without instrument changeover.
• Robust multi-residue capability supports high throughput screening while meeting regulatory maximum residue limits (MRLs).
• Enhanced laboratory efficiency by consolidating analyses and minimizing sample preparation complexity.

Future Trends and Possibilities of Use

Potential developments may further expand the utility of APGC/MS/MS in pesticide analysis:

• Integration with automated sample preparation and data-processing workflows for greater throughput.
• Method adaptation to detect non-volatile or thermally labile compounds by combining APGC with alternative chromatographic techniques.
• Development of ultra-trace detection methods for emerging contaminants in complex food matrices.
• Creation of comprehensive multi-residue libraries to streamline rapid screening and identification.

Conclusion

APGC/MS/MS on the Waters Xevo TQ-S platform provides a powerful, reliable, and efficient solution for trace-level pesticide residue analysis in fruits and vegetables. The method achieves low detection limits, excellent linearity, and minimal matrix interference, supporting regulatory compliance and operational flexibility within analytical laboratories.

References

• Roberts D., Wallace A. Quantitative Analysis of Pesticides in QuEChERs Extracts Using APGC/MS/MS. Waters Corporation; 2013.