Precision pesticide residue detection in food: Unleashing the power of dual channel LC - Orbitrap Exploris EFOX mass detector

Importance of the topic

The reliable detection and quantitation of pesticide residues in food matrices is essential for consumer safety, regulatory compliance, and international trade. Modern multi-residue workflows must combine sensitivity, wide compound coverage, robustness across diverse matrices, and the ability to support both targeted quantitation and retrospective/suspect screening as regulatory lists evolve.

Objectives and study overview

This application demonstrates the capability of the Thermo Scientific Orbitrap Exploris EFOX mass detector operated in full-scan high-resolution mode coupled to a dual-channel Vanquish LC system to quantify 577 pesticide compounds in acetonitrile QuEChERS extracts. The study reports analytical qualification data: limits of quantification (LOQs), linearity, precision, accuracy, and robustness across representative fruit and vegetable matrices.

Methodology

- Sample extraction: QuEChERS AOAC 2007.01 extraction with dedicated clean-up (Thermo Scientific QuEChERS AOAC 2007.01 Method Clean-Up Kit).
- Calibration: three pesticide mixtures prepared in acetonitrile; calibration curves over 1–100 ppb (lower calibration point varied by compound at 1, 2, 5, or 10 ppb). Each compound qualified with at least five independent calibration curves (R2 > 0.990; relative amount deviation ≤40% at LOQ and ≤20% for other levels).
- Injection/workflow: dual-channel LC (Vanquish Duo) executes two dedicated gradients and alternating injections onto two columns (different geometries) so positive- and negative-ion-preferring compounds elute separately; a switching valve directs a single LC flow to the MS producing one combined data file. A low-volume strong solvent loop enables direct injection of QuEChERS extracts (no dilution/reconstitution required).

Used instrumentation

- LC: Thermo Scientific Vanquish Duo system with two independent binary pumps and injection ports; Vanquish Flex Binary UHPLC Pump; Vanquish Dual Split Sampler; Vanquish Flex Column Compartment; 35 µL mixer and strong solvent loop.
- Columns: Thermo Scientific Hypersil GOLD C18 Selectivity columns: 150 × 2.1 mm, 1.9 µm (positive mode column) and 100 × 2.1 mm, 1.9 µm (negative mode column).
- MS: Thermo Scientific Orbitrap Exploris EFOX Mass Detector (BRE725557). Key MS parameters: Full-scan acquisition, m/z 70–1,000, resolution 60,000, HESI source. LC peak width ~4 s; injection volume 1 µL. Mobile phases for both channels: 0.1 mM ammonium fluoride and 0.1% formic acid in water (A) and methanol (B).
- Software: Chromeleon 7.3.2 Chromatography Data System for method control, acquisition of alternating positive/negative injections into one data file, and integrated processing for targeted and suspect workflows.

Main results and discussion

- Scope and sensitivity: The workflow quantitatively covers 577 pesticides. Most compounds reached LOQs of 1 ppb in solvent and corresponding low µg/kg LOQs in matrices (QuEChERS fruits/vegetables/cereals). Some compounds required higher LOQs (e.g., 2, 5 or 10 ppb) depending on chemical properties.
- Linearity and accuracy: Calibration curves across five sets consistently met acceptance criteria (R2 > 0.990). Relative amount deviation charts confirmed compliance with ≤40% at LOQ and ≤20% at higher levels.
- Precision and repeatability: Representative LOQ repeatability (n = 5) showed low RSDs for many analytes (1–6%); a few compounds (e.g., dalapon) presented higher RSD (≈15%) at LOQ but remained within qualification limits.
- Robustness: A robustness study alternating matrix extracts (apple, tomato, carrot) with LOQ solvent QC injections every 10 samples showed stable quantitative performance across 40 consecutive injections without MS maintenance or retuning. Relative amount deviations remained within acceptance windows for both positive and negative injections.
- Chromatography advantages: The dual-column, dual-gradient approach separates positive- and negative-ionizing compounds into dedicated injections, improving sensitivity and peak shape by avoiding frequent polarity switching and mitigating solvent-mismatch effects for aqueous starts.

Benefits and practical applications

- Single-workflow capability for high-resolution full-scan quantitation and retrospective/suspect screening, enabling addition of new targets without re-acquiring samples.
- Regulatory readiness: demonstrated LOQs, linearity, precision, and robustness aligned with regulatory expectations (SANTE guidance), supporting routine MRL compliance testing.
- Increased laboratory productivity: direct injection of QuEChERS extracts (strong solvent loop) reduces sample handling and turnaround time; Chromeleon integration simplifies dual-injection acquisition and data processing.
- Broad applicability: suitable for routine monitoring in food control laboratories, QA/QC in food production, and surveillance of organic and conventional products.

Future trends and potential applications

- Wider adoption of HRMS full-scan workflows in routine regulatory labs for combined targeted and non-targeted screening, supported by expanding spectral libraries and suspect lists.
- Increasing use of dual- or multi-channel LC setups to optimize polarity-specific separations and increase MS duty cycle efficiency.
- Enhanced data processing: machine learning and automation to accelerate review, reduce false positives, and maximize value of retrospective analysis.
- Integrations with ion-mobility separation and orthogonal techniques to further improve isomer differentiation and lower matrix interferences.
- Continuous method extension to cover metabolite lists and emerging contaminants while lowering LOQs for more challenging analytes.

Conclusion

The presented dual-channel LC — Orbitrap Exploris EFOX full-scan workflow successfully quantifies a comprehensive set of 577 pesticides with demonstrated sensitivity, linearity, precision, and robustness across representative food matrices. The combined targeted quantitation and retrospective screening capability, direct QuEChERS injection, and the operational advantages of separate positive/negative injections make this approach attractive for regulatory and high-throughput food-residue testing laboratories.

Reference

1. European Commission. Directorate‑General for Health and Food Safety. Guidance document on analytical quality control and method validation procedures for pesticide residues in food and feed. SANTE/11312/2021. Implemented January 1, 2022.
2. Chromeleon CDS — pesticides solution. Thermo Fisher Scientific documentation.
3. Thermo Fisher Scientific. Application Brief 002783: An advanced integrated GC-MS/MS and LC-MS-MS workflow for the comprehensive analysis of pesticide residues in food.