Fluorometric determination of fipronil by integrating the advantages of molecularly imprinted silica and carbon quantum dots.

A fluorometric method is described for the determination of fipronil, a frequently-used insecticide. It exploits the blue fluorescence of carbon quantum dots (CQDs) and the selectivity of molecularly imprinted silica (MIS). The MIS was prepared via the sol-gel method by using fipronil as the template, 3-aminopropyltriethoxysilane as functional monomer, and tetraethoxysilane as cross-linker in the presence of CQDs. The blue fluorescence of the CQD@MIS, with excitation/emission peaks at 340/422 nm, is quenched by fipronil. The assay works in the 0. 70 pM to 47 μM fipronil concentration range, and the limit of detection is 19 pM. The method was successfully applied to the quantitation of fipronil in spiked eggs, milk, and tap water. Recoveries between 83.8 and 114.0% were achieved. The corresponding relative standard deviations (RSD) are less than 6.67%. Graphical abstractSchematic representation of a high sensitivite and selectivite fluorescence nanoprobe constructed by combining the excellent fluorescence property of carbon quantum dots and the predicted selectivity of molecularly imprinted silica. It was applied to analyze fipronil in egg, milk and tap water, respectively.