[Study on ratiometric determination of peroxynitrite and its scavenger based on synchronous fluorescence...

A ratiometric fluorimetry is proposed for the determination of peroxynitrite (ONOO-) and the evaluation of its scavenger based on synchronous fluorescence spectroscopy. L-tyrosine, an intrinsic fluorescent aminoacid, reacts with peroxynitrite and carbon dioxide, yielding a highly fluorescent dimer of tyrosine in pH 8.5 PBS buffer solution. By synchronous fluorescence scanning, both monomer and dimer emission bands of L-tyrosine appeared at 364 and 406 nm, respectively. The ratio of F406/ F364 is quantitatively related to the concentration of peroxynitrite, where F406 represents the intensity of synchronous emission band of dimer and F364 represents that of monomer. The method has been showing merit of being insensitive to the changes in experimental parameters and offers a higher sensitivity and a broader responding linear range of the analyte concentration, compared to fluorimetric method, giving a LOD of 1.84 X 10(-8) mol x L(-1) and a linear range of 1.60 X 10(-7) mol x L(-1)-6.00 X 10(-6) mol x L(-1) for ONOO-, respectively, with a deviation of 2.4% for 1.00 X 10(-6) mol x L(-1) ONOO- (n = 8). A IC50 of 0.065 microg x mL(-1) for mitoxantrone, an antioxidant and anticancer drug, was also obtained. This method has proved to be simple and speedy. It would be easily used in the determination of ONOO- and its scavenger.