THE EFFECT OF MICELLES ON THE STEADY-STATE AND TIME-RESOLVED FLUORESCENCE OF INDOLE, 1-METHYLINDOLE, AND 3-METHYLINDOLE IN AQUEOUS-MEDIA

3-Methylindole (skatole) is a component of animal waste and is, conseq uently, a primary component in odor problems arising in livestock mana gement, notably swine production, The ability to probe and to exploit the interactions of 3-methylindole with micelles has important implica tions for monitoring and controlling odor problems. The effect of a su rfactant (Brij-35) on the fluorescence properties of indole, 1-methyli ndole, and 3-methylindole in aqueous solutions is reported. Steady-sta te fluorescence spectra reveal a blue shift in the emission as the sur factant concentration is increased, while the absorption spectra are p ractically unaffected, Time-resolved fluorescence measurements reveal shorter average lifetimes for 3-methylindole (3-MI) as the Brij-35 con centration is increased, The fluorescence decay of 3-MI in water is de scribed well by a single exponential, whereas, at the highest Brij-35 concentration, a triple exponential is necessary to describe the fluor escence decay. The contributions of each component in the fluorescence decay are used to determine the extent of 3-MI partitioning into the micelle phase, It is found that 93% of the 3-MI molecules partition in to the micelle at the highest Brij-35 concentration used, The equilibr ium constant for the association between the micelles and the 3-MI mol ecules is determined to be 2.6 x 10(4) M-1. In addition, the reduction of 3-MI in the vapor phase by addition of a dry surfactant, lecithin, is also demonstrated.