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

Significance of the topic

Pesticide residue testing is critical to ensure food safety, regulatory compliance, and consumer health. The QuEChERS sample preparation method, coupled with advanced chromatographic techniques, offers a rapid, cost-effective, and versatile workflow for multiresidue analysis of diverse food matrices. Integrating both GCxGC-TOFMS and LC-MS/MS allows comprehensive screening of volatile, non-volatile, and polar pesticides as well as non-target compounds.

Objectives and overview of the study

The study aimed to assess the ruggedness and performance of QuEChERS extraction across commodities with varying water, fat, and pigment contents (red bell pepper, cucumber, grape, spinach, lemon, raisin, hazelnut). Fortified with over 200 pesticides, samples were analyzed by GCxGC-TOFMS and LC-MS/MS to compare recovery, selectivity, and the ability to quantify incurred residues and detect non-target analytes.

Methodology and instrumentation

A modified EN 15662 QuEChERS protocol was applied: samples were homogenized, fortified, extracted with acetonitrile and buffering salts, followed by dispersive SPE cleanup (PSA and C18). Dried matrices were re-hydrated prior to extraction. Final extracts were directly injected for GCxGC-TOFMS or diluted tenfold for LC-MS/MS quantification using solvent standards (LC) or matrix-matched standards (GC).

Instrumentation

• GCxGC-TOFMS: LECO Pegasus 4D with Rxi-5Sil MS and Rtx-200 columns; helium carrier; modulation time 4 s; EI at 70 eV; acquisition 45–550 amu at 100 spectra/s.
• LC-MS/MS: Shimadzu UFLCXR and AB SCIEX 4000 QTRAP; Ultra Aqueous C18 column; water/ammonium acetate and methanol/ammonium formate gradient; ESI in positive/negative mode; Scheduled MRM.

Main results and discussion

Both GCxGC-TOFMS and LC-MS/MS achieved recoveries of 80–110% for most pesticides in water-rich matrices (pepper, cucumber, grape, spinach). Complex samples (lemon, raisin, hazelnut) exhibited interferences: GCxGC-TOFMS selectivity was insufficient for low-mass ions (propoxur, siduron, buprofezin), and LC-MS/MS suffered ion suppression in acidic or high-lipid extracts, resulting in low recoveries or non-detects (e.g., lemon LC recoveries ~40%). Incurred residues showed good agreement between platforms. GCxGC-TOFMS facilitated non-target pesticide identification, including endosulfans and endosulfan sulfate.

Benefits and practical applications of the method

• Rapid, low-cost QuEChERS extraction adaptable to diverse foods.
• GCxGC-TOFMS provides enhanced separation for volatile and semi-volatile pesticides and non-target screening.
• LC-MS/MS excels with polar, thermally labile analytes and high selectivity via MRM.
• Combined platforms support robust QA/QC in food safety, environmental monitoring, and regulatory testing.

Future trends and applications

• Integration of high-resolution mass spectrometry for improved non-target analysis.
• Enhanced cleanup strategies (e.g., cartridge SPE, graphitized carbon removal) for complex matrices.
• Automation and miniaturization of sample preparation workflows.
• Extension to emerging contaminants and real-time screening in field settings.

Conclusion

The QuEChERS approach, combined with GCxGC-TOFMS and LC-MS/MS, delivers a powerful multiresidue screening and quantification workflow. While each technique has specific limitations in complex matrices, their complementarity ensures broad analyte coverage and reliable detection. Ongoing enhancements in cleanup and instrumentation will further strengthen pesticide residue analysis.

Reference

1. Anastassiades M., Lehotay S.J., Stajnbaher D., Schenck F.J., J. AOAC Int., 86 (2003) 412.
2. Lehotay S.J., de Kok A., Hiemstra M., Van Bodegraven P., J. AOAC Int., 88 (2005) 595.
3. Lehotay S.J., Mastovská K., Yun S.J., J. AOAC Int., 88 (2005) 630.
4. Mastovská K., Dorweiler K.J., Lehotay S.J., Wegscheid J.S., Szpylka K.A., J. Agric. Food Chem., 58 (2010) 5959.
5. EN 15662, Foods of Plant Origin—Determination of Pesticide Residues by GC-MS/LC-MS/MS (2008).
6. Cochran J., Thomas J., Kowalski J., Misselwitz M., Lake R., GN AN1338, Restek (2011).
7. Jansson C., Pihlström T., Österdahl B., Markides K.E., J. Chromatogr. A, 1023 (2004) 93.
8. Payá P., Anastassiades M., Mack D., Sigalova I., Tasdelen B., Oliva J., Barba A., Anal Bioanal Chem., 389 (2007) 1697.
9. Kittlaus S., Schimanke J., Kempe G., Speer K., J. Chromatogr. A, 1218 (2011) 8399.