Dissipation profile and risk assessment of diflubenzuron and novaluron in tomato fruits under greenhouse conditions

Abstract

A simple liquid-liquid extraction (LLE) procedure and liquid chromatography-tandem mass spectrometer (LC-MS/MS) were validated to analyze the residues of diflubenzuron and novaluron in tomatoes. Validation criteria included; linearity in the range of 2–100 μg.kg−1 and 5–200 μg.kg−1 with a correlation coefficient (R2) of ≥ 0.998, trueness (% recovery) of 90.55–97.51% at spiking levels of 10, 100, and 1000 mg.kg−1, the limit of detection (LOD) of 0.46 and 3.22 μg.kg−1, the limit of quantitation (LOQ) of 5 and 10 μg.kg−1, intraday repeatability (RSDr) of 9.31% and 6.63%, and inter-day repeatability (RSDR) of 13.72% and 8.87%, respectively for diflubenzuron and novaluron. Due to the matrix effect, negligible enhancement in instrument response was observed for the tested analytes. The dissipation behaviour of diflubenzuron (24 % SC) and novaluron (10 % EC) in greenhouse tomatoes after treatment with 192 and 40 g a.i. ha-1 (authorized dosage) and 336 and 80 g a.i. ha-1 (high dosage) was investigated. Dissipation kinetics were best fitted to the first-order reaction. Despite the application dose for novaluron being about three times smaller compared to diflubenzuron, the residues of novaluron dissipated more rapidly than those of diflubenzuron with constant rates (k) of 0.342–0.356 and 0.194–0.154 day-1 and half-lives (t0.5) of 1.77–1.73 and 3.57–4.49 days respectively, at the doses tested. The terminal residues of diflubenzuron and novaluron were 0.013–0.328 and 0.011–0.171 mg.kg-1 after 2 and 3 times application, respectively. The calculated risk quotients were less than 1, indicating that spraying tomatoes with the tested insecticides at the applied doses poses no significant potential risks to Saudi consumers.