Ferrofluid-based liquid-phase microextraction: Analysis of four phenolic compounds in milks and fruit juices

A novel liquid-phase microextraction based on the ferrofluid was successfully applied for the extraction and determination of four phenolic compounds (bisphenol-A, bisphenol-AF, tetrabromobisphenol-A and 4-tert-octylphenol) in milks and fruit juices. In this study, a range of alkyl (C4-C10) alcohols as the carrier liquid were used for the preparation of ferrofluids. The study showed that an appropriate chain length of alkyl alcohol may improve the extraction efficiency and maintain the integrity of ferrofluids during extraction, so 1-heptanol (C7) was selected as the optimal carrier liquid. Specifically, the effects of various parameters on the extraction of phenolic compounds were investigated and optimized. Under the optimized conditions, the limits of detection were between 0.35 and 0.66 μg L−1. The intra-day and inter-day precision (RSD %) for the analytes at 10 and 50 μg L−1 were in the range of 3.2-6.7 % and 2.9-7.1%, respectively.