Construction of selective aqueous two-phase systems based on 4-sulfothiacalix[4]arene sodium and imidazolium bromide

Aqueous two-phase system (ATPS) has been considered a green separation system, and its extraction performance in practical applications is related to its selectivity for the target. However, the selectivity of ATPS towards target molecules is not satisfactory so far. Thus, developing selective ATPS is both meaningful and challenging. Calixarenes are biocompatible, and multiple functions can be integrated into a calixarene-based platform. In the present study, we developed selective ATPSs using 4-sulfothiacalix[4]arene sodium (STC[4]) and imidazole ionic liquid ([C n mim]Br). It is found that the [C n mim]Br/STC[4] ATPS exhibits high selectivity towards theobromine, the [C n mim]Br/trisodium citrate/STC[4] and PEG 400/trisodium citrate/[C n mim]Br/STC[4] ATPSs exhibit high selectivity towards vanillin, and the PEG 400/(NH 4 ) 2 SO 4 /[C n mim]Br/STC[4] ATPS exhibits high selectivity towards syringic acid. Therefore, selective ATPSs targeting different bioactive molecules present in nature can be developed by modifying the composition of [C n mim]Br/STC[4]-based ATPSs.