Solubility of l-serine, l-threonine and l-isoleucine in aqueous aliphatic alcohol solutions

The solubilities of l-serine, l-threonine and l-isoleucine in the aqueous systems of ethanol, 1-propanol and 2-propanol were measured at 298.15, 313.15 and 333.15 K by means of gravimetric and spectrophotometric ninhydrin based method measurements.In order to represent the solid–liquid equilibria in those systems the excess solubility approach was combined with the NRTL, the modified NRTL, the modified UNIQUAC equations and also with the model presented by Gude et al. [M.T. Gude, L.A.M. Wielen, K.Ch.A.M. Luyben, Fluid Phase Equilibr. 116 (1996) 110–117]. Their correlation performance showed global average relative deviations of 15.3, 13.7, 13.4 and 15.8%, respectively, while their application in the prediction of l-threonine solubility in water/ethanol mixed solvent mixtures, at two different temperatures, showed average relative deviations of 18.8, 9.1, 28.9, and 38.4%, respectively.