OPTICAL-ABSORPTION STUDIES OF THE KINETICS OF UV-INITIATED AND SELF-INITIATED AUTOXIDATION OF LINOLEATE MICELLES

Autoxidation of linoleate micelles in aqueous alkaline solutions was s tudied by absorption spectroscopy. Autoxidation was initiated in eithe r a UV-induced or a spontaneous decomposition (self-initiation) of hyd roperoxides, initially present as trace impurity. In both cases, the h ydroperoxides, the primary oxidation products, increased quadratically with time. In the presence of vitamin E, UV irradiation initially cau sed an exponential photodecomposition of hydroperoxides, with a rate c onstant of 2.6 . 10(-3) s(-1), towards a Stationary level. The period of inhibition of autoxidation by vitamin E was in proportion to the am ount of vitamin E added to the solution. In the course of autoxidation , when the concentration of hydroperoxides exceeded a certain critical level, the micelles collapsed, which was monitored by light scatterin g. A model for the consumption of vitamin E, in the case of UV initiat ion, was developed and from which an initiation rate of 4.05 . 10(-7) M . s(-1) was derived. From the initiation rate and the coefficient of the second-order dependence of hydroperoxides with time, an oxidizibi lity of 1.28 (M . s)(-1/2) was derived.