Increasing throughput of the LC-MS analysis of pesticide residues in food

Importance of the topic

Comprehensive and rapid detection of pesticide residues in food is critical for ensuring consumer safety, meeting regulatory limits, and maintaining analytical laboratory productivity. With modern pesticides often polar or thermally labile, LC-MS/MS has become the preferred technique, but high sample throughput remains a bottleneck.

Objectives and overview of the study

This application note describes the development and validation of a dual-channel UHPLC-MS/MS workflow to increase sample throughput in multi-residue pesticide analysis without sacrificing chromatographic resolution or data quality. The goal was to reduce cycle time per injection and demonstrate method performance across various food matrices.

Methodology

• Sample preparation: QuEChERS citrate buffer extraction of 10 g fruit/vegetable test portions, followed by salt addition, centrifugation, and dilution with water containing dimethoate-d6 injection standard.
• Dual-channel chromatography: Two parallel Accucore C18 columns operated with synchronized overlapping gradients. A defined “data window” triggers MS data acquisition only during analyte elution, routing off-window eluent to waste.
• Gradient conditions: 0–2 min at 2% B, ramp to 30% B at 2 min, to 50% B at 3 min, to 100% B at 11 min, hold to 14 min, then re-equilibration.
• MS acquisition: TSQ Altis triple quadrupole in SRM mode, positive/negative electrospray, optimized voltages, gas flows, and dwell times (min. 5 ms).
• Calibration: Intra-channel and cross-channel linear calibrations (1/X weighting) covering 273 pesticides, evaluated for linearity and precision.

Instrumentation

• UHPLC: Thermo Scientific Vanquish Duo with dual independent pumps and injectors.
• Columns: Thermo Scientific Accucore C18, 100 mm × 2.1 mm, 2.6 μm, 30 °C.
• MS: Thermo Scientific TSQ Altis triple quadrupole with OptaMax NG ion source.
• Software: Thermo Scientific Aria MX for method synchronization and TraceFinder for data processing.

Main results and discussion

The dual-channel method achieved a 70 % increase in throughput (137 injections/24 h vs. 80 injections/24 h single-channel) by reducing cycle time from 18 to 10.45 min. Retention times remained stable within ±0.1 min over 120 injections. Calibration curves for channels 1 and 2, and cross-channel, showed R2>0.9998. Recovery and repeatability in apple, bell pepper, and orange at 0.01 and 0.1 mg/kg complied with DG SANTE criteria (recoveries 70–120 %, RSD<20 %). Six proficiency test samples produced z-scores ≤2 with no false positives/negatives.

Benefits and practical applications

• Substantially higher laboratory throughput without loss of resolution or sensitivity.
• Efficient use of MS acquisition time via synchronized dual-channel operation.
• Cross-channel calibration reduces calibration workload.
• Validated performance for regulatory compliance in routine food safety and quality control.

Future trends and potential applications

Emerging developments may integrate dual-channel LC with high-resolution MS for broader analyte panels, automated sample handling, and AI-driven data analysis. Expansion to other residue classes (veterinary drugs, mycotoxins) and multidimensional separations could further enhance throughput and specificity.

Conclusion

The dual-channel UHPLC-MS/MS approach provides a validated, high-throughput solution for multi-residue pesticide analysis in food, achieving significant time savings while maintaining robust chromatographic and quantitative performance.

References

• DG SANTE. Analytical quality control and method validation procedures for pesticide residues analysis in food and feed. SANTE/12682/2019.
• Rajski L, Elicone C, Fussell RJ et al. Dual-channel chromatography: A smart way to improve the analysis efficiency in liquid chromatography coupled to mass spectrometry. J Chromatogr A. 2020;1633:461614. DOI:10.1016/j.chroma.2020.461614