Fluorescence quenching studies on the interaction of riboflavin with tryptophan and its analytical application

The ineraction between riboflavin (RBF) and tryptophan (Trp) was investigated using fluorescence spectroscopy and UV–vis absorption spectroscopy under physiological conditions. The fluorescence of Trp was quenched by RBF via dynamic quenching, which was analyzed using the Stern–Volmer relation. The value of the Forster distance R₀ (2.31 nm) was obtained according to the Forster's theory of nonradiative energy transfer. Under physiological conditions, a linear relationship could be established between the quenched fluorescence intensity of Trp and the concentration of RBF in the range of 5.8 × 10^‐7–2.0 × 10^‐5 mol/L. The detection limit was 1.8 × 10^‐7 mol/L. The method was successfully applied to determine riboflavin concentrations in pharmaceutical samples. Copyright © 2012 John Wiley & Sons, Ltd.