Evaluation of nanoflow liquid chromatography high resolution mass spectrometry for pesticide residue analysis in food

- First report on the use of nanoflowLC-nanoESI-HRMS for pesticide multiresidue analysis.
- Use integrated emitters provides an enhancement of method precision and ruggedness.
- Limits of quantitation in the low ng kg−1 range (ca. 1000-fold lower than MRLs).
- Sensitivity achieved enables the use of high dilution factors (1:50 or beyond).
- Negligible matrix effects so that matrix-matched calibration is no longer required.

This article reports on the evaluation of nanoflow liquid chromatography-mass spectrometry (LC-MS) for pesticide residue analysis in food. The approach is based on the use of reversed-phase C18 nano columns with an integrated emitter, so that separation, ionization and detection are performed minimizing dead volumes. The use of nanoflow not only increases ionization efficiency and minimizes ionization suppression but also boost sensitivity compared to analytical-scale LC-MS methods. The nanoflow LC system was combined with full-scan high resolution mass spectrometry using a Q-Exactive Orbitrap instrument. The analytical performance was assessed for over 60 representative pesticides in five representative commodities (tomato, baby food, orange, fruit-based jam and olive oil). The sensitivity achieved with this configuration enables the implementation of high dilution factors (eg. 1:20, 1:50 or beyond) in pesticide residue workflows without compromising sensitivity, featuring limits of quantitation in the low ng kg−1 range. Using this dilution factors, signal suppression was found negligible in most cases (< 10% in most cases, especially with 1:50 dilution), so that matrix-matched standards may be skipped, thus simplifying laboratory workflows. The robustness of the nanoflow LC system and its capability to withstand long analytical runs was also evaluated. Appropriate precision in terms of peak area and retention time was obtained at different concentration levels for over 125 injections without any instrument servicing. The main benefits of the nanoflow liquid chromatography approach are the high sensitivity gain and the outstanding reduction in matrix effects thanks to the high sample dilution factors that can be implemented, along with the substantial reduction in solvent usage.