Rapid and sensitive detection of fipronil and its metabolites in edible oils by solid-phase extraction based on humic acid bonded silica combined with gas chromatography with electron capture detection.

Solid-phase extraction based on humic acid bonded silica followed by gas chromatography with electron capture detection was developed to determine fipronil and its metabolites in edible oil. To achieve the best extraction performance, we systematically investigated a series of solid-phase extraction parameters. Under the optimized conditions, the method was validated according to linearity, recovery, and precision. Good linearities were obtained with R(2) more than 0.9996 for all analytes. The limits of detection were between 0.3 and 0.5 ng/g, and the recoveries ranged from 83.1 to 104.0% at three spiked concentrations with intra- and interday relative standard deviation values less than 8.7%. Finally, the proposed method was applied to determine fipronil and its metabolites in 11 edible oil samples taken from Wuhan markets. Fipronil was detectable in four samples with concentrations ranging from 3.0 to 5.2 ng/g. In China, the maximum residue limits of fipronil in some vegetables and maize are 20 and 100 ng/g (GB/T 2763-2014), respectively. The residues of fipronil and its metabolites in commercial edible oils might exhibit some potential threat to human health as a result of high consumption of edible oil as part of daily intake.