An Assessment of GC Orbitrap MS Technology for the Routine Screening and Quantification of Pesticide Residues in Food

Importance of the Topic

Monitoring pesticide residues in food matrices is critical for consumer safety and regulatory compliance. High resolution mass spectrometry coupled to gas chromatography offers comprehensive full scan data with high mass accuracy, enabling sensitive detection of a broad range of analytes in complex samples.

Study Objectives and Overview

This study evaluated the performance of the Thermo Scientific Exactive GC Orbitrap system for routine screening and quantification of 51 pesticides in tomato, leek and orange samples. All analyses were conducted according to European SANTE guidelines for residue analysis.

Methodology and Instrumentation

Sample preparation followed an acetate buffered QuEChERS protocol. Key steps included:

• Extraction with acetonitrile and addition of magnesium sulfate and PSA for cleanup.
• Final extracts reconstituted in ethyl acetate at 1 g per milliliter matrix equivalent.
• Calibration from 0.5 to 500 micrograms per kilogram, including matrix matched standards.

The analytical system comprised:

• Gas chromatograph: Trace 1310 GC with single taper liner, helium carrier at 1.2 milliliter per minute and oven program from 40 to 300 degrees Celsius.
• Mass spectrometer: Exactive GC Orbitrap operating in full scan mode (50 to 550 Da) at 60 000 resolving power (full width at half maximum) and electron ionization at 70 electron volts.
• Data processing: Thermo TraceFinder software for automated peak detection, calibration and quality control flagging.

Main Results and Discussion

Chromatographic separation yielded distinct total ion chromatograms for each matrix. Mass accuracy remained below 0.6 parts per million across individual scans. Limits of identification met SANTE criteria at 5 micrograms per kilogram for all but a known degrading compound. Limits of detection reached 1 microgram per kilogram for 93 percent of analytes. Linearity exceeded 0.99 in all cases. Repeatability tests of ten replicates at 10 micrograms per kilogram showed percent relative standard deviations below 10 percent. A 100 injection sequence over 66 hours demonstrated stable sensitivity (RSD below 6 percent) and maintained mass accuracy below 1 part per million.

Benefits and Practical Applications

Use of Orbitrap full scan provides:

• Enhanced selectivity and confidence in compound identification due to sub-ppm mass accuracy.
• Unlimited scope screening without preselecting target compounds.
• Improved laboratory throughput by combining qualitative and quantitative information in a single run.

Future Trends and Potential Applications

Emerging directions include coupling high resolution GC MS data with machine learning algorithms for suspect and non target screening, expanding databases for environmental contaminants, and integrating automated workflows to further streamline regulatory testing.

Conclusion

The Exactive GC Orbitrap mass spectrometer demonstrated robust performance for routine pesticide residue analysis in fruits and vegetables. It achieved sub-ppm mass accuracy, low detection limits, excellent linearity and repeatability in accordance with SANTE guidelines, supporting high confidence screening and quantification in complex matrices.

Reference

1. SANTE 11945 2015 Guidance document on analytical quality control and method validation procedures for pesticide residues analysis in food and feed Supersedes SANCO 12571 2013 Implemented by 01 01 2016
2. Belmonte Valles N Retamal M Martinez Uroz MA Mezcua M Fernandez Alba AR de Kok A Determination of chlorothalonil in difficult to analyse vegetable matrices using various multiresidue methods Analyst 2012 137 10 2513 2520