Utilization of High Resolution LC-MS for Screening and Quantitative Analysis of Pesticides in Food Matrix using a Q Exactive Bench Top Orbitrap Platform

Importance of the topic

Modern agriculture relies heavily on pesticides to ensure crop yield and quality. However, residual pesticides in food can pose significant health risks to consumers and must be monitored at trace levels to comply with stringent regulatory standards worldwide. High-throughput and reliable analytical methods are essential to support food safety programs and laboratory workflows.

Objectives and overview of the study

The study aimed to demonstrate the capability of a bench-top Q Exactive Orbitrap high-resolution mass spectrometer for simultaneous quantitative analysis, confirmation and both targeted and untargeted screening of 60 pesticides in a complex food matrix (green bell pepper). The work evaluates linearity, sensitivity, specificity and workflow efficiency in a single chromatographic run.

Methodology and instrumentation

Sample preparation used a modified QuEChERS protocol: 15 g homogenized peppers extracted with acetonitrile, followed by cleanup and dilution steps prior to spiking with standards.

• Liquid chromatography: Thermo Scientific Accela 1250 U-HPLC system with Hypersil GOLD aQ C18 column (100×2.1 mm, 1.9 μm); gradient from 98% water/2% methanol (0.1% formic acid, 10 mM ammonium formate) to 100% methanol over 10 min; flow rate 300 µL/min; column at 40 °C; 5 µL injection.
• Mass spectrometry: Q Exactive Orbitrap; full-scan MS (m/z 120–1000) at 75 000 resolution; data-dependent MS/MS at 35 000 resolution; positive ESI, spray voltage 3800 V, sheath gas 32, aux gas 7, capillary and vaporizer at 295 °C; mass tolerance ±5 ppm.

Main results and discussion

Calibration curves for all 60 pesticides in spiked matrix exhibited excellent linearity (R²>0.99) across low-ppb concentrations without significant matrix interferences. Recoveries were consistent and reproducible. Targeted screening based on accurate mass and retention time confirmed all analytes in a single run. Untargeted screening identified additional compounds, such as chlorpyrifos oxon, using isotopic pattern matching and elemental composition assignment. The combined workflows provided both qualitative and quantitative data with high confidence.

Benefits and practical applications

This unified approach offers several advantages for food safety and QA/QC laboratories:

• Single-run quantitative, confirmatory and screening analysis reduces instrument time and sample consumption.
• High resolution and mass accuracy minimize false positives and improve specificity.
• Untargeted screening capability uncovers unexpected contaminants without additional method development.

Future trends and potential uses

Advances in high-resolution MS are expected to expand pesticide monitoring to more diverse food matrices and environmental samples. Integration with automated data processing and machine learning could further accelerate unknown screening. Emerging ambient ionization techniques and miniaturized HRMS instruments may enable on-site testing in the field or at production sites.

Conclusion

The bench-top Q Exactive Orbitrap coupled with ExactFinder software delivers a powerful, streamlined workflow for comprehensive pesticide analysis in food. It combines high sensitivity, accurate quantitation and broad screening in one method, meeting the modern demands of food safety monitoring.

Reference

• Yang C, Ghosh D, Wang J, Akervik K. Utilization of High Resolution LC-MS for Screening and Quantitative Analysis of Pesticides in Food Matrix using a Q Exactive Bench Top Orbitrap Platform. Thermo Fisher Scientific; 2011.