Quantitative analysis of pyrazole pesticides in tea leaf using FastGC-HRTOFMS

Significance of the Topic

Fast gas chromatography combined with high‐resolution time‐of‐flight mass spectrometry (FastGC‐HRTOFMS) offers rapid, sensitive and accurate screening of pesticide residues in complex food matrices. This approach addresses regulatory demands for low detection limits and high throughput in food safety monitoring.

Objectives and Study Overview

The study aimed to develop and validate a FastGC‐HRTOFMS method for simultaneous qualitative and quantitative determination of four pyrazole pesticides (Fipronil, Ethiprole, Pyraflufen ethyl, Tebufenpyrad) in tea leaf samples. Emphasis was placed on achieving rapid analysis while maintaining sensitivity, mass accuracy and reproducibility.

Methodology

Sample Preparation

• Tea leaves (5 g) extracted by a multiresidue protocol from the Japanese Ministry of Health, Labour and Welfare.
• Spiked at 0.01, 0.05 and 0.1 ppm in extract (equivalent to 4, 20 and 40 ppb in tea leaf).
• Triplicate injections per concentration for reproducibility assessment.

Chromatographic and Mass Spectrometric Conditions

• FastGC with a short column and rapid temperature ramp.
• High‐resolution TOFMS acquisition with narrow m/z window (±0.05 Da).
• Data recorded in full scan mode for exact mass determination and extraction of high resolution chromatograms.

Instrumentation Used

JEOL JMS‐T100GCV FastGC‐HRTOFMS system equipped with:

• Short high‐efficiency GC column for rapid separation.
• High‐resolution time‐of‐flight mass analyzer capable of m/z accuracy to four decimal places.
• Software for high‐resolution mass chromatogram generation and quantitative calibration.

Results and Discussion

Mass Spectra and Selectivity

• At 4 ppb equivalent, Fipronil ion m/z 254.9704 was baseline resolved from a coeluting matrix ion at m/z 255.21, illustrating the selectivity advantage over low‐resolution MS.

Chromatographic Performance

• High resolution extracted ion chromatograms for each pesticide at 4 ppb showed signal‐to‐noise ratios of 17 to 292, ensuring reliable detection near or below MRLs (2 ppb for Fipronil, 10 ppb for Pyraflufen ethyl).

Linearity and Reproducibility

• Calibration curves exhibited correlation coefficients (r2) above 0.997 for all four analytes over the studied range.
• Precision (n=3) yielded coefficients of variation below 11.9% at 4 ppb, improving to below 4% at higher levels.

Practical Benefits and Applications

The method combines sub‐minute chromatographic runs with high‐resolution mass detection to deliver rapid screening of pesticide residues. It supports regulatory compliance and high‐throughput laboratories by reducing analysis time while preserving sensitivity and accuracy.

Future Trends and Applications

Emerging developments may include:

• Automation of sample preparation to increase throughput.
• Extension to other pesticide classes and complex food matrices.
• Integration with real‐time data processing and artificial intelligence for automated screening.
• Coupling FastGC‐HRMS with ambient ionization techniques for direct analysis.

Conclusion

The FastGC‐HRTOFMS approach on the JMS‐T100GCV platform enables rapid, sensitive and reproducible quantification of pyrazole pesticides in tea leaf. The method meets stringent regulatory requirements and offers substantial workflow efficiencies for routine food safety testing.

References

1. M. Ubukata et al., Abstract of the 97th conference of the Japanese Society for Food Hygiene and Safety, page 20 (2009)