Experimental measurements and thermodynamic modelling of aqueous solubilities, octanol-water partition coefficients and vapor pressures of dimethyl phthalate and butyl benzyl phthalate

The aqueous solubilities, the octanol-water partition coefficients and the vapor pressures of two food contaminants (dimethyl phthalate-DMP and butyl benzyl phthalate-BBP) have been determined in this work. The aqueous solubility measured by the dynamic saturation method [298.15–328.15 K] were in the order of 10⁻⁴ mol fraction for DMP and 10⁻⁷ for BBP. The octanol-water partition coefficient is measured by using the 'shake-flask’ method at 298.15 K. It is found that the BBP molecule is highly hydrophobic. The vapor pressure measurements carried out with the dynamic gas saturation method between 313.15 and 423.15 K, were validated with DMP vapor pressure measurements by using a static apparatus. The vapor pressures of DMP ranged from 1.4 to 1668 Pa for temperatures between 313.15 and 423.15 K, while BBP exhibits lower vapor pressures ranging from 0.014 Pa at 343.15 K to 24 Pa at 423.15 K. The experimental data determined in this work are compared with calculated properties issued from different thermodynamic models (UNIFAC, UNIQUAC, NRTL, COSMO-SAC dsp). It is found that the UNIQUAC and NRTL models can well describe the experimental aqueous solubility, while larger deviations were found for UNIFAC and COSMO-Sac dsp. The COSMO-SAC dsp model can better predict the octanol-water partition coefficient of the studied molecules than the UNIFAC model.