Dissipation kinetics, decontamination and risk assessment of spiromesifen in/on green chillies

Abstract

Results of a supervised field trial to study the dissipation of spiromesifen on chillies are reported. Spiromesifen 22.9 SC @ 96 and 192 g a.i. ha−1 were sprayed twice at 15 d interval from fruit initiation stage and fruit samples collected at 0 (1 h), 1, 3, 5, 7, 10, 15 and 21 d after second spray along with the control samples. A method with accepted specificity (% RSD < 2), good linearity (R2 = 0.992), recovery (84.14-95.20 %) and satisfactory repeatability was developed. The LOQ and LOD of spiromesifen on chillies by UHPLC with binary gradient of CH3CN and H2O, 70:30 in an isocratic flow were 0.015 and 0.05 μg g−1 respectively. The mean initial deposits after two sprayings of spiromesifen in/on green chillies @ 96 and 192 g a.i ha−1 were 0.934 and 1.696 μg g−1, respectively. More than 80 per cent of spiromesifen residues dissipated in 3 d after treatment. The residues persisted up to 5 d @ 96 g a.i ha−1 and 7 d @ 192 g a.i ha−1. Dissipation of spiromesifen followed the first order reaction kinetics and the calculated half life was 1.36 and 1.40 d, respectively for the two respective doses, with safe waiting periods of 3.83 and 4.99 d. Washing with tap water + boiling at 100 °C (2 min + 10 min) led to 91.03 per cent reduction of residues. TMRC values of spiromesifen being less than the MPI at the recommended dose, it will not cause any ill effect on consumption of green chillies.