Determination of fipronil and its metabolites in chicken egg by dispersive liquid–liquid microextraction with 19F quantitative nuclear magnetic resonance spectroscopy

Abstract

A novel and sensitive dispersive liquid–liquid micro-extraction (DLLME) combined with 19F quantitative nuclear magnetic resonance spectroscopy (qNMR) method was developed and validated for determination of fipronil and its metabolites in chicken egg. The qNMR analysis was carried out under the optimum experimental conditions including deuterated DMSO as solvent, calibrated 4′-Bromo-2′-fluoro acetanilide as internal standard, d1 (relaxation delay) = 1 s, and NS (number of scan) = 1024. The analytes were extracted in a mixed emulsion system of extraction solvent (chloroform) and dispersing solvent (acetonitrile). A demulsifier (acetonitrile) was added to break up the emulsion. Then, the lower layer (chloroform) was collected and analyzed by qNMR. Important parameters affecting the extraction efficiency of DLLME were investigated in detail. Although the pretreatment time is relatively long, we have obtained satisfactory experimental results. The newly established method has a good linear relationship, the linear correlation coefficient r is between 0.9972 and 0.9995, the minimum detection limit is 0.025 μg mL−1, and the extraction reproducibility is good (RSD ≤ 3.67%, n = 6). The optimized new method was applied to the analysis of fipronil and its metabolites in chicken egg. The recoveries of spiked samples were between 97.49% and 103.0%, and satisfactory experimental results were obtained. The obtained results show that the establishment of this method provides an excellent alternative for the detection of fipronil and its metabolites in chicken egg.