A multiresidue pesticide method using a modified quadrupole-Orbitrap MS for quantitation, screening and confirmation

Importance of the Topic

The reliable detection and quantitation of multiple pesticide residues in olive oil is essential for ensuring food safety and compliance with international regulatory limits. High-resolution accurate mass (HRAM) spectrometry coupled with robust sample preparation delivers the sensitivity, accuracy, and speed required by modern testing laboratories.

Objectives and Study Overview

This study presents a comprehensive workflow for the analysis of over 500 pesticide residues in olive oil. It integrates a modified QuEChERS sample preparation protocol with liquid chromatography–HRAM mass spectrometry on a quadrupole-Orbitrap platform. The goal is to provide a rapid, user-friendly method that meets or exceeds EU regulatory validation criteria for quantitation, screening, and confirmation.

Methodology and Instrumentation

Sample Preparation
The method employs a streamlined QuEChERS extraction without dispersive solid-phase clean-up. Olive oil is extracted into acetonitrile, yielding low matrix interference. A 1 µL injection volume optimizes sensitivity and robustness.

Used Instrumentation

• Vanquish Flex Binary UHPLC system with Accucore aQ column (100 × 2.1 mm, 2.6 µm) operated at 25 °C, flow rate 300 µL/min, 15 min gradient.
• Orbitrap Exploris 240 MS with full-scan resolution of 45,000 and DIA at 15,000, polarity switching (negative 2.5 kV, positive 3.5 kV), sheath gas 30, auxiliary gas 6, sweep gas 1, ion transfer tube 290 °C, vaporizer 350 °C.
• Mobile phases: A – water with 5 mM ammonium formate and 0.1% formic acid; B – methanol with 5 mM ammonium formate and 0.1% formic acid.
• Data processed in Thermo Scientific™ TraceFinder™ software using an mzCloud-based spectral library and retention time database for over 700 standards.

Main Results and Discussion

• Calibration: Matrix-matched standards spanned 0.5–100 ppb (up to 500 ppb for certain analytes). Over 95% of compounds achieved linearity with r² > 0.99.
• Limits of Quantitation (LOQs) and Detection (LODs) met EU SANTE guidelines, with LOQs below maximum residue limits for all target analytes.
• Confirmation criteria: At least one or two fragment ions per compound with accurate mass matching within 3 ppm and consistent ion ratio thresholds, even at 0.5–1 ppb levels.
• Method robustness: More than 1,000 injections demonstrated stable retention times, peak shapes, and response factors over extended sequences.

Benefits and Practical Applications of the Method

This approach enables high-throughput screening and quantitation of broad pesticide panels in routine food safety labs. The minimal sample preparation and low injection volume reduce consumable costs and instrument downtime. Automated data processing streamlines reporting and confirmation workflows.

Future Trends and Opportunities

• Expansion of spectral libraries to cover emerging pesticides and metabolites.
• Integration with laboratory automation and online sample cleanup for increased throughput.
• Application of machine learning algorithms for real-time data review and anomaly detection.
• Adaptation of the workflow to other complex matrices such as seeds, nuts, or fruit purees.

Conclusion

A validated multiresidue method combining modified QuEChERS extraction and quadrupole-Orbitrap HRAM MS delivers sensitive, accurate, and robust analysis of over 500 pesticide residues in olive oil. The workflow meets regulatory performance criteria, supports high throughput, and is suited for routine food safety testing.

References

• Barbetti F., Yang C., Klaas C., D’Adonna D., Ghosh D. A multiresidue pesticide method using a modified quadrupole-Orbitrap MS for quantitation, screening and confirmation. Thermo Fisher Scientific, 2018.