AbstractLiquid–liquid equilibrium (LLE) data of aqueous poly(ethylene glycol) (PEG) 2000–sodium citrate systems were determined experimentally at 25°, 35° and 45 °C. Experimental techniques and analytical methods were described in the previous article (T. Murugesan, M. Perumalsamy. J. Chem. Eng. Data. 2005; 50, 1392–1395 [22]). The NRTL (nonrandom, two‐liquid) model, expressed in mass fraction, was used to correlate the LLE of aqueous two‐phase systems (ATPS). The interaction energy parameters of the NRTL model were adjusted using these experimental LLE data. The model described experimental equilibrium data with a good agreement. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.