Solubility of Parabens in Subcritical Water

The solubility of methyl, ethyl, and butyl parabens (4-hydroxybenzoate) in water was determined at (298, 373, 423, and 473) K using a homemade heating/mixing system and by high performance liquid chromatography analysis. The solubility increased for all three parabens studied when water temperature was raised from 298 K to 423 K. However, the solubility decreased with a further temperature increase from 423 K to 473 K. This was due to the degradation of parabens at 473 K as revealed by a separate study. A new model was developed to guide the estimation of paraben solubility in subcritical water. The solubility values predicted using this new model compare reasonably well with our experimental values.