Non-targeted Screening and Accurate Mass Confirmation of 510 Pesticides on the High Resolution Exactive Benchtop LC/MS Orbitrap Mass Spectrometer

Significance of the Topic

Pesticide residue monitoring is critical due to expanding agricultural trade and increasingly strict global regulations. Rapid, sensitive, and cost-effective methods are required to ensure food safety and compliance at low parts-per-billion levels.

Study Objectives and Overview

This study evaluated a non-targeted screening workflow for 510 multi-class pesticides using ultra-high-performance liquid chromatography (U-HPLC) coupled to a Thermo Scientific Exactive benchtop Orbitrap mass spectrometer. The aim was to achieve fast separation, high mass accuracy, and robust confirmation without extensive compound-specific optimization.

Methodology and Instrumentation

Sample preparation employed a modified QuEChERS extraction of spiked spinach. Chromatography used a Thermo Scientific Accela U-HPLC system with a Hypersil GOLD aQ C18 column (100×2.1 mm, 1.9 µm). Mobile phases were water/0.1% formic acid/4 mM ammonium formate (A) and methanol/0.1% formic acid/4 mM ammonium formate (B), at 300 µL/min. The gradient delivered 510 analytes in a 12-minute run. A Thermo Scientific Exactive Orbitrap MS operated in full-scan (100–1500 m/z), 50,000 resolving power, and automatic gain control (AGC 1e7), with heated electrospray ionization in positive/negative switching mode.

Main Results and Discussion

All 510 pesticides were separated and detected within 12 minutes. Mass deviations were under 5 ppm for most analytes without internal recalibration. Limits of quantitation (LOQs) for 499 compounds met or exceeded the 10 ppb regulatory threshold. High resolving power enabled clear discrimination of isobaric pairs (e.g., atrazine vs. cymoxanil). In spinach extracts, method detection limits (LODs) were below 0.3 ppb and LOQs below 1 ppb, with calibration linearity (R2) exceeding 0.99.

Benefits and Practical Applications

• High throughput with 12-minute cycle times for broad-scope screening
• Non-targeted full-scan acquisition accommodates unlimited analytes
• High resolution ensures confident separation of isobaric interferences
• Mass accuracy enables reliable positive identification
• Reduced method development compared to targeted MS/MS workflows

Future Trends and Applications

Advances may include integration of suspect screening libraries, retrospective data mining of archived full-scan data, and application to diverse food and environmental matrices. Automated spectral matching and machine learning will further accelerate decision support in regulatory and industrial laboratories.

Conclusion

The U-HPLC Exactive Orbitrap MS platform delivers a rapid, sensitive, and robust solution for comprehensive pesticide residue analysis at regulatory levels. Its ease of use and non-targeted capability make it well suited for routine compliance testing and emerging screening needs.

References

• US EPA Pesticide Reassessment and FQPA Accomplishments, 2007
• National Standard GB 2763-2005 Maximum Residue Limits for Pesticides in Food, China, 2005
• Japan MHLW Positive List System for Agricultural Chemicals, 2006
• EU Regulation No. 396/2005 Harmonized Pesticide MRLs, 2008
• EU Directive 91/414/EEC Pesticide Safety Review, 2009
• Thermo Scientific Application Note 30163 Food and Feed Analysis Using Orbitrap MS, 2008
• Thermo Scientific Application Note 30162 Exactive Orbitrap for Benchtop LC/MS, 2008
• AOAC Official Method 2007.01 QuEChERS Extraction for Pesticide Residues
• US EPA Method Detection Limit Procedure, 40 CFR Part 136, App B