Indole In Aqueous Solution Research Articles

Lumiflavin-sensitized photooxygenation of indole.

Abstract— The lumiflavin‐sensitized photooxygenation of indole in aqueous solutions has been investigated by means of steady light photolysis and flash photolysis. The semiquinone of lumiflavin and the half‐oxidized radical of indole were formed by the reaction between triplet lumiflavin and indole (3.7 times 109M‐1 s‐1). The semiquinone anion radical of lumiflavin reacted with oxygen to form superoxide radical. The triplet state of lumiflavin also reacted with oxygen forming singlet oxygen, 1O2. But the reaction between 1O2 and indole (7 times 107 M_l s_1; estimated from steady light photolysis using Rose Bengal as a sensitizer) was far less efficient than the reaction between indole and triplet lumiflavin. The quantum yield of the lumiflavin‐sensitized photooxygenation of dilute indole via radical processes was much higher than that via1O2 processes, though appreciable 1O2 was formed.

Diazotised sulphanilic acid as a spectrophotometric reagent for the determination of trace amounts of indole in aqueous solution

A spectrophotometric method for the determination of trace amounts of indole in aqueous solution is described. The method is based on the coupling reaction of the determinand with diazotised sulphanilic acid to form, in an acidic medium, an intense yellow, water-soluble, stable azo dye, which shows maximum absorption at 445 nm. The graph of absorbance versus concentration in linear, indicating that Beer's law is obeyed over the range 30–90 µg of indole in a final volume of 25 ml, i.e., 1.2–3.6 p.p.m., with a molar absorptivity of 33.4 × 103 l mol–1 cm–1, a sensitivity index of 0.0035 µg cm–2, a relative error of 0 to –1.6% and a relative standard deviation of 0.2–1.9%, depending on the determinand concentration. The optimum reaction conditions and interferences from foreign organic compounds have been investigated.

Excited states of flavines. V. The quenching of flavine luminescence by indoles.

Abstract— The quenching of the fluorescence of flavines by indoles in aqueous solution has been studied as a function of concentration, viscosity and temperature. The quenching shows a negative temperature dependence, and is in part diffusion controlled. Static and dynamic processes both contribute to quenching.In the presence of alcohol or denaturants static quenching is inhibited and dynamic quenching supervenes. The effect of indoles on the flavine fluorescence lifetimes and phosphorescence characteristics is consistent with the quenching mechanism proposed.