Aqueous solubility, vapor pressure and octanol-water partition coefficient of two phthalate isomers dibutyl phthalate and di-isobutyl phthalate contaminants of recycled food packages

Abstract

In this work, we studied the aqueous solubility, vapor pressures of dibutylphthalate (DBP) and di-isobutylphthalate (DIBP) as a function of temperature between 298.15 and 328.15 K and between 313.15 and 423.15 K respectively. The octanol-water partition coefficient was measured at 298.15 K using shake-flask method. For aqueous solubility, measurements were carried out using the dynamic saturation method and values ranges in 10−7 mol fraction with a relative higher solubility for DIBP regarding DBP. Solubility results are in good agreement with the octanol-water partition coefficient measurement showing that DBP is more hydrophobic than its isomer DIBP. For vapor pressure, after an interlaboratory validation step using static method performed with DBP in a temperature range between 381 and 421 K, measurements for both compounds DBP and DIBP using the gas saturation method presented a standard relative deviation lower than 2% and values ranged from 10−2 and 102 Pa. By combining vapor pressure and solubility results, we calculated Henry's law constant and air-water partition coefficient and showed an important deviation between the two isomers even at low temperature.