Fast and Ultrafast LC-MS/MS Methods for Robust and Reliable Analysis of Pesticides in Food Using the Vanquish UHPLC System

Significance of the Topic

Monitoring pesticide residues in food is critical for consumer safety and regulatory compliance. High-throughput, sensitive, and reproducible analytical methods are required to screen hundreds of compounds at low concentration levels. Combining ultrahigh‐performance liquid chromatography (UHPLC) with tandem mass spectrometry (MS/MS) and timed selected reaction monitoring (SRM) enhances sensitivity, peak definition, and data reliability.

Study Overview

This work compares two LC-MS/MS approaches for quantifying over 250 pesticides in complex food matrices: a 15-minute “fast” UHPLC method and a 5-minute “ultrafast” SRM method. Both methods were transferred and optimized on the Thermo Scientific Vanquish UHPLC system coupled to the TSQ Endura triple quadrupole MS. Performance metrics include retention time precision, throughput, and analytical figures of merit.

Methodology and Instrumentation

• Sample matrices: strawberry, leek, and wheat flour prepared by QuEChERS extraction with acetonitrile and water addition.
• Chromatography: Thermo Accucore aQ column (100 x 2.1 mm, 2.6 μm), binary water/methanol mobile phases with 5 mM ammonium formate and 0.1% formic acid.
• Gradient programs: 15-minute method at 0.3 mL/min and 5-minute method at 0.9 mL/min.
• Mass spectrometry: HESI source in positive/negative switching, timed SRM acquisition with scan windows of 30 s (fast) and 9 s (ultrafast), cycle times of 0.5 s and 0.34 s.
• Instrument: Thermo Scientific Vanquish UHPLC system, TSQ Endura MS, and Chromeleon 7.2 CDS software.

Results and Discussion

The fast and ultrafast methods displayed comparable data quality. A method transfer from an older RSLC system required only a brief isocratic hold to correct gradient delay, resulting in retention time shifts under 5 seconds. The ultrafast approach achieved 300% greater throughput by increasing flow rate to 0.9 mL/min and narrowing SRM windows. Run-to-run retention time relative standard deviations were below 0.30 s, and matrix-to-matrix variability remained under 0.15 s, enabling reliable narrow‐window SRM acquisition. Both methods met validation criteria for accuracy (80–120%), precision (RSD ≤15%), linearity, and limits of quantification at 5–100 μg/L.

Benefits and Practical Applications

• High throughput: 67% reduction in analysis time without sacrificing sensitivity.
• Enhanced sensitivity and reproducibility using timed SRM and ultrafast gradients.
• Robust method transfer with minimal adjustment between LC platforms.
• Applicable to routine food safety monitoring and regulatory compliance testing.

Future Trends and Applications

Further advances may include multiplexed sample preparation, automated data processing with artificial intelligence, and expansion to broader classes of agrochemicals. Integration with ultra-high-resolution mass analyzers and online sample clean-up techniques could push detection limits lower and streamline workflows for high-volume testing laboratories.

Conclusion

This comparison demonstrates that ultrafast UHPLC-MS/MS with narrow timed SRM windows on a Vanquish UHPLC system offers a robust, rapid, and reliable solution for multi-residue pesticide analysis. High retention time precision and optimized instrument parameters enable significant time savings and maintain stringent performance metrics.

Reference

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