Fluorescence quenching method for the determination of carbazochrome sodium sulfonate with aromatic amino acids.

In Britton-Robinson (BR) buffer medium (pH 3.3), carbazochrome sodium sulfonate (CSS) can react with some aromatic amino acids such as tryptophan (Trp), tyrosine (Tyr) and phenylalanine (Phe) to form a 1:1 complex by electrostatic attraction, aromatic stacking interaction and Van der Waals' force, resulting in fluorescence quenching of these amino acids. Maximum quenching wavelengths were located at 352 nm (CSS-Trp system), 303 nm (CSS-Tyr system) and 284 nm (CSS-Phe system), respectively. The fluorescence quenching value (ΔF) was proportional to the concentration of CSS in a certain range. The fluorescence quenching method for the determination of CSS showed high sensitivity, with detection limits of 31.3 ng/mL (CSS-Trp system), 44.6 ng/mL (CSS-Tyr system) and 315.0 ng/mL (CSS-Phe system), respectively. The optimum conditions of the reaction conditions and the effect of coexisting substances were investigated and results showed that the method had good selectivity. The method was successfully applied for the rapid determination of CSS in blood and urine samples. Based on the bimolecular quenching constant Kq , the effect of temperature and Stern-Volmer plots, this study showed that quenching of fluorescence of amino acids by CSS was a static quenching process.