Application of QuEChERS Technique With UHPLC-Q-TOF Tandem Mass Spectrometry for High-Throughput Screening Multiple Pesticides in Food Matrixes

Significance of the topic

Global authorities enforce strict maximum residue levels (MRLs) for pesticides in fruits and vegetables to protect public health. Rapid, sensitive, and reliable analytical protocols are essential for routine monitoring of hundreds of pesticide residues across diverse food matrices.

Study objectives and overview

This work aims to develop and validate a high-throughput screening method combining QuEChERS extraction with ultra high performance liquid chromatography coupled to quadrupole time-of-flight tandem mass spectrometry (UHPLC-Q-TOF-MS/MS). The method targets 281 pesticide compounds spiked into representative matrices (apple, tomato, cabbage) to assess performance in terms of identification confidence, quantitation accuracy, sensitivity, and applicability to real samples.

Methodology and used instrumentation

The sample preparation follows an optimized QuEChERS protocol:

• Homogenize 10 g of sample with 20 mL acetonitrile containing 1% acetic acid.
• Add 1 g sodium acetate and 4 g magnesium sulfate; shake 3 min, centrifuge 5 min.
• Cleanup 10 mL supernatant with 300 mg PSA sorbent; shake 3 min, centrifuge 5 min.
• Evaporate 5 mL extract under nitrogen at 40 °C; reconstitute in 1 mL water/acetonitrile/acetic acid (79.9:20:0.1); filter (0.22 µm).

Instrumental analysis employs an Agilent 1290 Infinity UHPLC system coupled to an Agilent 6530 Q-TOF with dual JetStream ESI. Key conditions:

• Column: ZORBAX SB C18, 2.1×100 mm, 3.5 µm; 40 °C.
• Mobile phases: water + 5 mmol/L ammonium acetate and 0.1% formic acid (A); acetonitrile (B); gradient from 1% to 90% B over 23 min.
• MS acquisition: full scan m/z 100–1600 at 4 spectra/s and targeted MS/MS m/z 50–1000 at 3 spectra/s; positive ion mode; reference masses m/z 121.0509 and 922.0098.

Main results and discussion

Optimization of extraction parameters ensured >96% of 75 representative pesticides achieved average recoveries above 80%, with 2 min shaking and 1% acetic acid in acetonitrile. PSA cleanup (300 mg) and reconstitution in 20:80 acetonitrile/water with 0.1% acetic acid maximized analyte recovery.

Accurate-mass database and spectral library searches yielded high identification scores (>90) for all 281 compounds at spiking levels of 5–20 µg/kg. Matrix effects were predominantly ion suppression; 10%–20% of compounds in cabbage showed >50% suppression, highlighting the need for matrix-matched calibration.

Linearity (R2 ≥0.99 for >95% compounds) and sensitivity (LOQs 0.01–4.5 µg/kg) met EU requirements (MRLs around 10 µg/kg). Recoveries for 98% of pesticides fell within 70%–120% and precision (RSD) was <20% across three matrices.

Screening 30 commercial samples detected 13 pesticides in 17 items. Five residues in seven samples and two residues in three samples exceeded the strictest EU MRLs, validating the method’s real-world applicability.

Benefits and practical applications

This combined QuEChERS–UHPLC-Q-TOF-MS/MS workflow offers:

• Simultaneous qualitative and quantitative screening of hundreds of pesticides.
• High throughput suited for routine QC/QA in food safety laboratories.
• Sensitivity and accuracy compliant with global regulatory limits.
• Automated data processing via accurate-mass databases and spectral libraries.

Future trends and potential applications

Further developments may include:

• Expansion to additional food matrices (grains, dairy, processed products).
• Integration with automated sample preparation platforms.
• Enhanced spectral libraries for emerging or degraded pesticide forms.
• Coupling with ion mobility or higher-resolution mass analyzers for improved selectivity.

Conclusion

The validated QuEChERS coupled UHPLC-Q-TOF-MS/MS method provides a robust, sensitive, and high-throughput solution for multi-pesticide screening in diverse food matrices. Its performance in terms of recovery, precision, sensitivity, and compliance with stringent MRLs supports its routine use in food safety monitoring.

References

1. Zhao Z, Shi Z, Kang J, Peng X, Fan C, Pang G. Chin. J. Chromatogr. 2013;31:372.
2. The International maximum residue level database. 2012-12-08.
3. Anastassiades M, Lehotay SJ, Štajnbaher D, Schenck FJ. J. AOAC Int. 2003;86:412–431.
4. Ferrer I, Thurman EM. J. Chromatogr. A. 2007;1175:24–37.
5. Koesukwiwat U, Lehotay SJ, Miao S, Leepipatpiboon N. J. Chromatogr. A. 2010;1217:6692–6703.
6. Polgár L, García-Reyes JF, Fodor P, et al. J. Chromatogr. A. 2012;1249:83–91.
7. Kmellár B, et al. J. Chromatogr. A. 2008;1215:37–50.