Assessment of Sodium Salt Anions ( and ) Influence on Caffeine Partitioning in Polyethylene Glycol and 1-Butyl-3-Methylimidazolium Tetrafluoroborate Based ATPS

Liquid-liquid equilibrium (LLE) data of aqueous polyethylene glycol (PEG) + sodium salt and ionic liquid (IL) + sodium salt two-phase systems (ATPSs) were determined experimentally at 298.15 K and atmospheric pressure (91 kPa), applying PEG 1500, 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]), sodium sulfate (Na2SO4) and sodium nitrate (NaNO3) as phase-forming components. PEG and IL based ATPSs were applied for caffeine partitioning study and the influence of sodium salt anions ( and ) on LLE data and on caffeine partitioning was investigated. All LLE data were successfully correlated by the Othmer-Tobias and Hand equations. Results indicate that the sulfate salt anion () influence on the phase formation ability follows the Hofmeister Series (HS) in both PEG and the IL-based ATPSs studied (Na2SO4 > NaNO3). Related to the LLE data, except for IL + Na2SO4 + H2O ATPs, caffeine addition showed no significant changes. Higher partition coefficients (varying from 7.758 to 16.289) were observed when using the aqueous PEG 1500 + Na2SO4 system.