Enhancement of Surfactants on Performance of PEG 400/Salt Aqueous Two-Phase System

PEG/salt aqueous two-phase systems (ATPSs) are the most common ATPSs because they are nontoxic, biocompatible, and inexpensive; however, the limited polarity difference between the two phases hinders their application. Although increasing the molecular weight of PEG can increase the polarity difference between the two phases, the significant viscosity of the PEG phase makes mass transfer difficult once the PEG molecular weight is too high. In the present study, we focus on enhancing the performance of low-molecular-weight PEG (PEG 400)/salt ATPS by using different ionic surfactants as adjuvants; the surfactants include anionic surfactants sodium dodecyl sulfate and sodium dodecyl benzenesulfonate, cationic surfactant dodecyl trimethylammonium bromide, and zwitterionic surfactant N-dodecyl-N, N-dimethyl-3-ammonio-1-propanesulfonate. It is found that all of these surfactants can promote the PEG 400/salt ATPS formation, but their effects on the ATPS extraction performance are different. By using tryptophan and vanillin as model extracts, it is found that the anionic and zwitterionic surfactants significantly enhance the extraction performance of PEG 400/salt ATPS, while the cationic surfactant significantly reduces the ATPS extraction performance. These results illustrate the potential of anionic and zwitterionic surfactants as adjuvants in enhancing the performance of low-molecular-weight PEG/salt ATPS.