Residue Analysis of Etoxazole in Red Pepper using Gas Chromatography: Application to Dissipation Pattern

A major modification of the QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) method was developed to analyze etoxazole in red pepper using gas chromatography coupled with nitrogen-phosphorus detector (GC-NPD). Etoxazole was extracted with acetonitrile, partitioned with magnesium sulfate, and purified with a solid phase extraction (SPE) cartridge. The method showed good linearity with a determination coefficient (R2) of 0.998 for the 0.02–2.0 mg/L concentration range. The method was validated using blank red pepper spiked at 0.2 and 1.0 mg/kg, and the average recovery rate was 74.4–79.1% with relative standard deviations < 5% for intra- and inter- day precision. The limits of detection (LOD) and quantification (LOQ) were 0.007 and 0.02 mg/kg, respectively. The developed method was successfully applied to field incurred samples, and etoxazole residues were confirmed using gas chromatography/mass spectrometry (GC/MS).