Validation of QuEChERS method for the determination of 36 pesticide residues in fruits and vegetables from Ghana, using gas chromatography with electron capture and pulsed flame photometric detectors

Abstract

In this study, “Quick, Easy, Cheap, Effective, Rugged and Safe” ‘QuEChERS’ method was modified for the determination of 36 pesticides fortified at (0.01–1.0) mg kg⁻¹ in three vegetables and a fruit (lettuce, carrot, tomatoes and pineapples respectively) from Ghana. The method involved extraction with acetonitrile, phase separation with primary secondary amine and magnesium sulfate; the final injection solution was reconstituted in ethyl acetate. Organochlorine and synthetic pyrethroids residues were detected with electron capture detector whereas organophosphorus, pulsed flame photometric detector was used. The recoveries at different concentration levels (0.01, 0.1 and 1.0 mg kg⁻¹) were in the range of 83% and 93% with relative standard deviation ranging from 2% to 10% (n = 5) and the coefficient of determination (R²) was greater than 0.99 for all the 36 pesticides. The method was successfully tested on 120 real samples from Accra markets and this proved to be useful for monitoring purposes particularly in laboratories that have no gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry.

Keywords:

• Validation
• pesticides
• ethyl acetate
• gas chromatography-electron capture detector
• gas chromatography-pulsed flame photometric detector

Acknowledgments

The authors thank Chemistry Department, University of Ghana and Pesticide Residues Laboratory, Ghana Standards Authority, Accra for technical support.

Funding

The authors are very grateful to anonymous friends for financial support for this study.