Molecularly Imprinted Polymeric Sorbent for Targeted Dispersive Solid-Phase Microextraction of Fipronil from Milk Samples

Fipronil, a phenyl pyrazole insecticide, is extensively used in agriculture to control insect infestation. It has the potential to assimilate into the food chain, leading to serious health concerns. We report molecularly imprinted polymer (MIP)-based dispersive solid phase microextraction for the targeted determination of fipronil in milk samples. Designing such a sorbent is of paramount importance for measuring the accurate amount of fipronil for monitoring its permissible limit. Response surface methodology based on a central composite design following a face-centered approach was used to optimize experimental conditions. The maximum binding capacity of 47 mg g-1 was achieved at optimal parameters of time (18 min), temperature (42 degrees C), pH (7), and analyte concentration (120 mg L-1). Under these conditions, a high percentage recovery of 94.6 +/- 1.90% (n = 9) and a low limit of detection (LOD) and limit of quantitation (LOQ) (5.64 x 10-6 and 1.71 x 10-5 mu g mL-1, respectively) were obtained. The MIP was well characterized through a scanning electron microscope (SEM) as well as Brunauer-Emmett-Teller (BET), Fourier transform infrared spectroscopy (FTIR), and thermogravimetric analysis (TGA) methods. Adsorption kinetics of the MIP followed the pseudo-first-order model (R2 0.99 and chi 20.96), suggesting the MIP-analyte interaction to be a physiosorptive process, while adsorption isotherms followed the Freundlich model (R2 0.99). The real sample analysis through high-performance liquid chromatography (HPLC) confirmed the selective determination of fipronil from milk samples.