Abstract
A rapid, simple, inexpensive, and reliable vortex-assisted dispersive liquid-liquid microextraction (VA-DLLME) method was developed for the determination of fipronil and its major metabolite, fipronil sulfone, in tomato fruits using liquid chromatography tandem mass spectrometry (LC-MS/MS). No salting-out or cleanup steps were required after extraction. Average recoveries ranged from 89.8 to 96.3% with relative standard deviation (RSD) values below 11.6%. The limit of quantitation (LOQ) of the method was 0.25 μg/kg, which is 20 times below the European Union-defined maximum residue limit (MRL) of 5 μg/kg. Good linearity was achieved, with a correlation coefficient ≥ 0.996 based on matrix-matched calibration. We investigated the dissipation and residue distribution of fipronil in tomato fruits after one application of suspension concentrate (SC) or emulsifiable concentrate (EC) formulations over 28 days under field conditions using the VA-DLLME method. The half-life (t1/2) of fipronil dissipation was 2.4 and 2.8 days, and the estimated pre-harvest interval (PHI) was 23 and 32 days for the SC and EC formulation, respectively. A risk assessment was conducted by evaluating the health risk index (HRI); the estimated PHIs values indicate it is safe to consume tomatoes after the recommended application of fipronil.
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