Analysis of cypermethrin residues and its main degradation products in soil and formulation samples by gas chromatography-electron impact-mass spectrometry in the selective ion monitoring mode

Abstract

A fast, simple and inexpensive sample preparation method based on the matrix solid-phase extraction (SPE) technique is proposed for the isolation of cypermethrin and its metabolite residues from soils. Both the extraction and clean-up procedures were carried out in two steps and target compounds were determined by gas chromatography coupled with electron-impact mass spectrometry (GC-EI/MS). The characteristic ions and fragmentation mechanism of cypermethrin were evaluated by electron impact ionization mass spectrometry (EI/MS). After the optimization of different parameters, such as the extraction solvent, the pesticide was extracted from the matrix with methanol/acetone in a Soxhlet extractor, cleaned up on a Florisil column by elution with a mixture of 30% ethyl acetate in n-hexane and analyzed by gas chromatography-electron impact ionization mass spectrometry (GC-EI/MS) in the selected ion-monitoring mode (SIM) with permethrin as internal standard. Recovery was in the range 77–118% with relative standard deviations (RSD) between 2.5% and 10.2%. The limit of detection (LOD) was 6.5 µg/kg for cypermethrin. The developed method was linear in the injection range 6–30 ng, with correlation coefficients greater than 0.9957.

Keywords:

• pesticide residues
• soils
• formulations
• cypermethrin
• solid-phase extraction
• gas chromatography-mass spectrometry

Acknowledgements

The authors are grateful to the Director's Office of Berkane for providing the necessary facilities. They also thank Mr. Chaieb Elbekkaye for his help with sample preparation. Financial support from the Spanish Ministry of Science and Innovation (Project CTQ2010-15027) and the Junta de Comunidades of Castilla-La Mancha (PEIC11-0022-7430) are gratefully acknowledged.