Residue determination and decline pattern of abamectin and fenpyroximate in okra fruits: a prelude to risk assessment

Abstract

This study developed and validated an LC-MS/MS analytical method for determining abamectin and fenpyroximate residues in okra fruits. The method optimization focused on chromatographic separation and ionization conditions, adding formic acid and ammonium formate to enhance ionization efficiency and signal sensitivity. Validation was performed according to SANTE guidelines, demonstrating good selectivity, linearity (R² > 0.998), precision, recovery, and minimal matrix effects (14.6% for abamectin and 5.2% for fenpyroximate). The limit of detection (LOD) was set at 0.0006 mg kg⁻¹ for abamectin and 0.0002 mg kg⁻¹ for fenpyroximate, while the limit of quantification (LOQ) was 0.002 mg kg⁻¹ and 0.001 mg kg⁻¹, respectively. Precision was within acceptable limits, with intra-day RSD of 11.4% for abamectin and 7.6% for fenpyroximate. Recovery ranged from 84.2% to 98.6%, meeting the acceptable 70–120% range. Persistence studies indicated that abamectin and fenpyroximate residues dissipated over time, with half-lives of 2.3 and 2.45 days, respectively. The pre-harvest interval (PHI) required for residues to fall below the maximum residue limit (MRL) was estimated to be 2.6 days for abamectin and 6.9 days for fenpyroximate. The risk quotient was assessed based on the Egyptian adult consumers' consumption of okra, ensuring a negligible risk.