Abstract
In a micellar solution of sodium dodecyl sulfate (SDS), it was found that the shifts of the absorption maxima of alkylparabens depended on the concentration of the surfactant, but not on the concentrotion of the drugs. The first derivative absorption spectrum was used to evaluate the wavelength shift, from which the distribution prarmeter and partition coefficient of the drug were calculated.The method was applied to find the distrbution parameters of the alkylparaben-cetyl-trimethylammonium bromide (CTAB) system, the alkylparaben-polyoxethylene (20) sorbitan monolaurate (Tween 20) system, and the alkyl gallate-CTAB system. In CTAB and Tween 20 solutions, the order of magnitude of the distribution parameter of alkylparaben was butyl->propyl->ethyl->methylparaben, and that of alkyl gallate was propyl->ethyl gallate, and these tendencies were independent of the temperature in the range from 25 to 60 °C (in the case of CTAB).
