A NEW STRATEGY FOR THE DETERMINATION OF CAPTAN AND FOLPET INFOOD MATRICES

Significance of the Topic

Monitoring pesticide residues such as captan and folpet in food matrices is critical for food safety and regulatory compliance. Traditional GC-MS methods suffer from analyte degradation and poor repeatability, necessitating more robust analytical strategies.

Objectives and Study Overview

The study aimed to develop and validate an LC-MS/MS method incorporating electrospray ionization (ESI) and a novel UniSpray source to quantify captan, folpet, and their degradation products THPI and PI in challenging food matrices such as kale and celery.

Methodology

The sample preparation involved an extraction and clean-up protocol optimized for plant matrices.

• Extraction solvents and matrices: kale and celery spiked at 0.005–0.100 mg/kg.
• Clean-up steps to remove interferences prior to analysis.

Instrumentation

• LC System: ACQUITY UPLC I-Class.
• MS System: Xevo TQ-XS.
• Column: ACQUITY BEH C18 (2.1×50 mm, 1.7 µm).
• Ion sources: Electrospray (capillary 3 kV, desolvation 200 °C) and UniSpray (impactor 3 kV, desolvation 300 °C).
• Mobile phase: water and methanol with 0.1% formic acid and 0.05% ammonia, gradient elution.
• Flow rate: 0.45 mL/min; injection volume: 10 µL.

Key Results and Discussion

Comparative GC-MS data showed rapid degradation of captan and folpet under splitless injection. In contrast, both LC-ESI-MS/MS and LC-UniSpray-MS/MS delivered high repeatability (RSD < 10% for 25 injections) and excellent linearity (R² > 0.995).

• Limits of detection were well below EU MRLs (e.g., 0.030 mg/kg for kale, 0.060 mg/kg for celery).
• UniSpray provided increased ionization efficiency and higher peak areas compared to ESI.
• Calibration curves for both analytes in complex matrices demonstrated reliable quantification.

Benefits and Practical Applications

• Offers a robust alternative to GC-MS for thiophthalimide fungicides.
• Enables simultaneous detection of parent compounds and degradation products.
• Applicable to routine QA/QC workflows and regulatory monitoring.

Future Trends and Opportunities

Emerging ionization techniques like UniSpray may be further adapted for multi-residue screening of challenging analytes. Integration with high-throughput platforms and automation can enhance laboratory efficiency. Further method extension to other compound classes may expand analytical coverage.

Conclusion

The validated LC-MS/MS workflow using ESI and UniSpray delivers reliable, sensitive, and robust analysis of captan, folpet, and their metabolites in food matrices. UniSpray notably improves ionization and detection limits, ensuring compliance with regulatory standards.

References

1. Berthet A., Bouchard M., Schupfer P., Vernez D., Danuser B., Huynh C.K. (2011) Liquid chromatography-tandem mass spectrometry (LC/APCI-MS/MS) method for the quantification of captan and folpet phthalimide metabolites in human plasma and urine. Anal Bioanal Chem, 399.
2. Lubin A., Bajic S., Cabooter D., Augustijns P., Cuyckens F. (2016) Atmospheric pressure ionization using a high voltage target compared to electrospray ionization. J. Am. Soc. Mass Spectrom, 28.
3. Lubin A., De Vries R., Cabooter D., Augustijns P., Cuyckens F. (2017) An atmospheric pressure ionization source using a high voltage target compared to electrospray ionization for LC/MS analysis of pharmaceutical compounds. J. Pharm. Biomed. Anal, 142.
4. European Union (2016) Commission Regulation (EU) 2016/156 amending Annexes II and III to Regulation (EC) No 396/2005 regarding maximum residue levels for boscalid, clothianidin, thiamethoxam, folpet and tolclofos-methyl. Off. J. Eur. Union.
5. European Union (2016) Commission Regulation (EU) 2016/452 amending Annexes II and III to Regulation (EC) No 396/2005 regarding maximum residue levels for captan, propiconazole and spiroxamine. Off. J. Eur. Union.