Validation of a QuEChERS-based gas chromatographic method for analysis of pesticide residues in Cassia angustifolia (senna)

ABSTRACT

A simple multi-residue method based on modified QuEChERS (Quick, Easy, Cheap, Effective, Rugged and Safe) approach was established for the determination of 17 organochlorine (OC), 15 organophosphorous (OP) and 7 synthetic pyrethroid (SP) pesticides in an economically important medicinal plant of India, Senna (Cassia angustifolia), by gas chromatography coupled to electron capture and flame thermionic detectors (GC/ECD/FTD) and confirmation of residues was done on gas chromatograph coupled with mass spectrometry (GC-MS). The developed method was validated by testing the following parameters: linearity, limit of detection (LOD), limit of quantification (LOQ), matrix effect, accuracy–precision and measurement uncertainty; the validation study clearly demonstrated the suitability of the method for its intended application. All pesticides showed good linearity in the range 0.01–1.0 μg mL⁻¹ for OCs and OPs and 0.05–2.5 μg mL⁻¹ for SPs with correlation coefficients higher than 0.98. The method gave good recoveries for most of the pesticides (70–120%) with intra-day and inter-day precision < 20% in most of the cases. The limits of detection varied from 0.003 to 0.03 mg kg⁻¹, and the LOQs were determined as 0.01-0.049 mg kg⁻¹. The expanded uncertainties were <30%, which was distinctively less than a maximum default value of ±50%. The proposed method was successfully applied to determine pesticide residues in 12 commercial market samples obtained from different locations in India.

KEYWORDS:

• Gas chromatograph
• organochlorine
• organophosphorus
• pesticides residues
• senna
• QuEChERS

Acknowledgments

The authors are grateful to the Director, ICAR-Directorate of Medicinal and Aromatic Plants Research (DMAPR), Anand, Gujarat, for providing necessary financial support and encouragement for conducting the study. The authors are also grateful to the Pesticide Residue Laboratory, Anand Agricultural University, Anand, for providing the instrumentation facility.