Effects of Polyvalent Alcohols on Partition Coefficients of Parabens between Aqueous and Oil Phases in Emulsion Type Cosmetics

The preservativity of emulsion type cosmetics was studied in terms of the partition coefficient of parabens in oil and aqueous phases. The partition coefficients of the parabens were first determined in a simple system, and in varied concentrations of dipropylene glycol and 1, 3-butylene glycol, and were then calculated in the oil phase; The concentration of paraben in the aqueous phase was then determined. As a result the partition coefficients of the parabens decreased exponentially with the increase of polyvalent alcohol concentrations. The polyvalent alcohols in sunscreen cream with high concentration of ultraviolet light absorbing oil remarkably increased the aqueous concentration of the paraben, which revealed from calculation. This result suggests that polyvalent alcohol may improve the preservativity of emulsions by increasing the aqueous concentration of parabens.