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Development and optimization of a thiol imidazolium-based ionic liquid for ultrasonic assisted liquid-liquid microextraction combined with HPLC-FLD for determination of bisphenols in milk and juice samples

Qu, Jingang, Li, Yanyan, Gao, Ming, Tan, Chengxia, Li, Jieyi, Wang, Xuedong, Wang, Huili
Lebensmittel-Wissenschaft + [i.e. und] Technologie 2019 v.111 pp. 653-662
acidity, bromine, centrifugation, chemical structure, cooling, detection limit, hydrophilicity, ionic liquids, juices, liquid-phase microextraction, mass spectrometry, milk, nuclear magnetic resonance spectroscopy, pH, screening, thiols, ultrasonics
Herein, a novel thiol imidazolium-based ionic liquid [C4MIM-SH]Br was synthesized by a facile three-step synthesis method, and its molecular structure was characterized by infrared (IR) spectra, 1H nuclear magnetic resonance (NMR) and mass spectrometry (MS). In addition to its merits as an ionic liquid, [C4MIM-SH]Br has strong acidity and high hydrophilicity. By integrating a conventional extractant ([CnMIM]PF6) with [C4MIM-SH]Br as a disperser, a whole ionic liquid microextraction was developed for determination of bisphenols (BPs). The main factors influencing extraction efficiency were optimized by Plackett-Burman design (PBD), single factor screening and central composite design as follows: 78 μL [C6MIM]PF6 as extraction solvent, 81 μL [C4MIM-SH]Br as disperser, 7 min ultrasound time, 13.5 min cooling time and 3min centrifugation time at 4000 rpm. Under optimized conditions, this method gave limit of detection for bisphenols in range of 0.13–0.82 μg L−1 in milk and juices, relative recoveries of 91.6–107.9%. Advantages of using [C4MIM-SH]Br as an independent disperser include avoiding an extra pH adjustment step, producing a rapid and clear layering phenomenon leading to convenient separation, and providing lower detection limits and higher extraction recoveries. Due to its multi-functions, [C4MIM-SH]Br has widespread application prospects in food analytical fields.