A Comprehensive Approach to Pesticide Residue Testing, Including Non-Target Analysis, for Fruits, Vegetables, and Nuts, Using QuEChERS, LC-MS/MS, and GCxGC-TOFMS

Importance of the Topic

Reliable detection of pesticide residues in fruits, vegetables, and nuts is essential for food safety and regulatory compliance. The combined use of rapid sample preparation and advanced analytical techniques enables laboratories to monitor a broad range of pesticide contaminants in complex food matrices with high throughput and confidence.

Objectives and Study Overview

This study evaluated a comprehensive workflow for pesticide residue analysis using QuEChERS extraction followed by both two-dimensional gas chromatography with time-of-flight mass spectrometry (GCxGC-TOFMS) and liquid chromatography tandem mass spectrometry (LC-MS/MS). Representative commodities with varying water, fat, pigment, and acidity levels were selected to assess method robustness.

Methodology and Instrumentation

The QuEChERS sample preparation followed the EN 15662 protocol, including acetonitrile extraction, salt partitioning, and dispersive solid phase cleanup (PSA/C18 dSPE). Two analytical platforms were employed:

• GCxGC-TOFMS: LECO Pegasus 4D system equipped with Rxi-5Sil MS (30 m × 0.25 mm × 0.25 µm) and Rtx-200 (1.5 m × 0.18 mm × 0.20 µm) columns, electron ionization (70 eV), modulation time 4 s, acquisition 45–550 amu at 100 spectra/s.
• LC-MS/MS: Shimadzu UFLCXR coupled to AB SCIEX 4000 QTRAP with Ultra Aqueous C18 column (100 mm × 2.1 mm, 3 µm), ESI ionization, Scheduled MRM transitions, gradient elution with ammonium acetate/formate buffers.

Main Results and Discussion

Average recoveries for most pesticides ranged from 80 to 110% across commodities by both methods. Citrus (lemon), dried fruit (raisin), and nuts (hazelnut) posed challenges due to coextractives and pigment load.

• GCxGC-TOFMS provided superior separation of coeluting analytes and non-target screening capabilities but suffered selectivity issues at low m/z in highly complex matrices.
• LC-MS/MS showed occasional ion suppression, particularly in lemon and hazelnut, leading to lower recoveries or non-detects for certain compounds.
• Incurred pesticide levels measured by both techniques were comparable, with each platform detecting compounds not amenable to the other.

Benefits and Practical Applications

The combined QuEChERS/GCxGC-TOFMS and LC-MS/MS approach delivers:

• High throughput multiresidue screening across diverse matrices.
• Comprehensive targeted quantification and non-target compound discovery.
• Adaptable workflows for regulatory compliance and quality control in food analysis.

Future Trends and Potential Uses

Advances may include more exhaustive cleanup strategies (e.g., cartridge SPE), higher-resolution mass spectrometry, improved column chemistries for balanced retention of polar analytes, and automated data processing for non-targeted screenings. Integration of orthogonal detection modes will further enhance confidence in trace-level pesticide monitoring.

Conclusion

This work underscores the complementarity of GCxGC-TOFMS and LC-MS/MS when paired with a robust QuEChERS sample preparation. Although challenging matrices require tailored cleanup or dilution strategies, the combined workflow achieves broad pesticide coverage and reliable quantification in complex food commodities.

References

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