Determination of bisphenolic pollutants in raw bovine milks and their derivative products using an in-situ metathesis reaction microextraction based on dicationic imidazolium-based ionic liquids

摘要

Herein, two dicationic imidazolium-based ionic liquids, (C-4(MIM)(2)]Br-2 and [C-6(MIM)(2)]Br-2, were synthesized and characterized, and then used in in-situ metathesis reaction microextraction procedures to assess their preconcentration/extraction performance for bisphenols in raw bovine milks and their derivative products. Three important parameters were screened using a Plackett-Burman design and optimized using central composite design, yielding the following optimized values: 0.04 g [C-6(MIM)(2)]Br-2 as extractant, 144 mu L LiNTf2 as ion-ex-change reagent and pH = 3. Under optimized conditions, this proposed method gave limits of detection of 0.29-1.90 mu g kg(-1), extraction recoveries of 87.49-98.64%, and inter-and intra-day precisions of 1.0-5.8% for four bisphenols (bisphenol A, B, AF and Z) in milks. The higher extraction efficiency of dicationic ionic liquids could be the result of stronger pi-pi interactions and higher hydrogen-bonding forces between them and bisphenols from two imidazolium rings. Among four bisphenolic species, bisphenol A was detected to be in the range of 0.66-1.27 mu g kg(-1) in all raw bovine milks, while in part of their derivative products and some milk products purchased from the market. Compared to previously reported methods, the newly developed method has the following advantages: high extraction efficiency, low limit of detection, and no use of organic solvents. Consequently, it is promissory to be applied in liquid milk samples for quality control in the future.