Rapid Screening and Quantitation of 240 Pesticides in Difficult Food Matrixes Using the Agilent 6545 Q-TOF Mass Spectrometer with the All Ions MS/MS Technique

Importance of the Topic

Screening for pesticide residues in food products is critically important for consumer safety and regulatory compliance. Complex food matrices such as black tea and high-fat commodities like avocado present analytical challenges due to co-extracted interferences. Advanced LC/MS workflows are needed to detect hundreds of pesticides at trace levels, meeting stringent maximum residue limits (MRLs) set by regulations worldwide.

Aims and Study Overview

This study evaluates an ultrahigh-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (UHPLC/Q-TOF MS) method employing the All Ions MS/MS technique to screen and quantify 240 pesticides and metabolites. Black tea and avocado matrices were selected to represent highly pigmented and lipid-rich samples, respectively. The goal was to demonstrate sensitive, high-throughput detection below regulatory MRLs without compound-specific method development.

Methodology and Instrumentation

Sample Preparation:

• Both black tea and avocado were prepared by a citrate-buffered QuEChERS extraction using Agilent BondElut kits.
• Avocado extracts underwent lipid removal by dispersive SPE; tea extracts were cleaned with graphitized carbon black.
• Extracts were spiked at six levels (1–100 ng/g) and diluted for UHPLC injection.

Chromatography and Mass Spectrometry:

• Agilent 1290 Infinity UHPLC with a ZORBAX Eclipse Plus C18 column (2.1 × 150 mm, 1.8 μm) operated at 45 °C, 0.4 mL/min gradient from 5% to 100% methanol over 22 minutes.
• Agilent 6545 Q-TOF with Jet Stream ESI in positive mode, optimized for 50–250 m/z All Ions MS/MS acquisition at three collision energies (0, 20, 40 V).
• Particle Swarm Optimization tuning enhanced ion transmission for small fragile molecules, improving sensitivity fourfold over classic autotune.
• Data acquired with MassHunter Acquisition B.06.01 and processed with MassHunter Qualitative B.07 and Quantitative B.07.

Main Results and Discussion

Detectability:

• At 10 ng/g spike level in tea (≈2 ppb) and avocado (10 ppb), 72% and 80% of pesticides were quantifiable, respectively, with calibration R²>0.99.
• Exemplary compounds benalaxyl (tea) and amidosulfuron (avocado) showed excellent quadratic fits and consistent fragment ratios across levels.

Data Analysis and Confirmation:

• All Ions MS/MS fragments were matched to a custom Personal Compound Database and Library (PCDL) using coelution scoring and accurate mass checks.
• MassHunter Qualitative provided visual review of precursor/product overlays, library match scores, and retention time alignment to minimize false positives.

System Robustness:

• Over seven days of continuous injections with complex matrices, system performance remained stable (average CV ≈7.6%).
• No significant carryover or sensitivity loss was observed, demonstrating reliable high-throughput operation.

Benefits and Practical Applications

• Comprehensive screening of hundreds of analytes in a single run without compound-specific MS/MS method setup.
• Retrospective data mining capability allows addition of new targets without re-analysis.
• Compliance with international MRLs and streamlined workflows reduce time and cost in food safety laboratories.

Future Trends and Potential Uses

Advances in high-resolution MS and data processing will extend All Ions MS/MS to broader contaminant classes (e.g., veterinary drugs, mycotoxins). Integration with machine learning can automate compound identification and flagging of novel residues. Further miniaturization and multiplexing will boost throughput in routine QA/QC and field testing environments.

Conclusion

The Agilent UHPLC/Q-TOF All Ions MS/MS approach provides a robust, sensitive, and flexible platform for rapid screening and quantitation of 240 pesticides in challenging food matrices. Combined with optimized ion transmission and advanced data analysis, this workflow meets regulatory requirements and enhances laboratory productivity.

References

1. Regulation (EC) No 396/2005 on maximum residue levels of pesticides in food and feed (2005, amended 2008).
2. US Code of Federal Regulations 40 CFR Part 180, Tolerance Information for Pesticide Chemicals.
3. Wuest B; Glauner T; Madden S; Taylor L; Payne T. Rapid Pesticide Screening Using All Ions MS/MS. Agilent Technologies Application Note 5991-2295EN.
4. European Commission SANCO/12571/2013, Guidance on analytical QC and validation procedures for pesticide residues.
5. Zhao L; Stevens J. Analysis of Pesticide Residues in Spinach Using BondElut QuEChERS AOAC Kit by LC/MS/MS. Agilent Technologies Application Note 5990-4248EN.