Applying ‘MRM Spectrum Mode’ and Library Searching for Enhanced Reporting Confidence in Routine Pesticide Residue Analysis (RAFA)

Significance of the Topic

Monitoring pesticide residues accurately is essential for food safety, compliance with regulations, and consumer protection. The expansion of multiple reaction monitoring (MRM) to include a broader set of fragment ion transitions enhances both selectivity and confidence in routine analyses.

Objectives and Study Overview

This study aims to evaluate an enhanced MRM Spectrum Mode combined with library searching to identify and quantify 193 pesticides in diverse agricultural matrices. It compares the new approach against conventional two-transition MRM workflows in terms of sensitivity, specificity, linearity, and reporting confidence.

Methodology and Instrumentation

Sample Preparation:

• Pesticide spiked matrices prepared by QuEChERS extraction without dilution
• Diverse samples including fruits, vegetables, spices, and herbal powders

Chromatography:

• UHPLC system (Nexera LC) with HSS T3 column (100 x 2.1 mm, 1.7 µm)
• Mobile phases: 5 mmol/L ammonium formate and 0.004% formic acid in water (A) and methanol (B)
• Gradient elution over 15 min; flow rate 0.4 mL/min; column temperature 40 °C; 0.1 μL injection with water co-injection

Mass Spectrometry:

• Triple quadrupole MS/MS with fast polarity switching (5 ms)
• MRM Spectrum Mode acquired up to 11 transitions per analyte (total 1,291 transitions)
• Dwell time 3 ms per transition

Main Results and Discussion

The enhanced method successfully monitored 193 pesticides with an average of seven transitions each, maintaining detection limits and linearity comparable to conventional methods. Library search similarity scores exceeded 99% across calibration levels (0.010–0.200 mg/kg), enabling clear differentiation of coeluting or isobaric compounds (e.g., desmedipham vs. phenmedipham). High throughput was preserved, with complete target coverage in a 15-minute run.

Benefits and Practical Applications

Key advantages include:

• Improved specificity and reduced false positives/negatives
• Robust quantification without compromise in sensitivity
• Versatile application across multiple food matrices
• Enhanced confidence via library-based confirmation

Suitable for routine regulatory and quality control laboratories requiring accurate multi-residue analysis.

Future Trends and Possibilities for Application

Ongoing developments may integrate high-resolution accurate-mass data, automated library updates with machine learning, and expanded libraries for emerging contaminants. Workflow automation and real-time data processing will further streamline pesticide monitoring.

Conclusion

The MRM Spectrum Mode combined with library searching offers a powerful enhancement to routine pesticide residue analysis by delivering higher specificity, consistent quantitation, and strong confidence in compound identification without sacrificing throughput or sensitivity.