FLUORESCENCE INVESTIGATION OF SOME FLUOROQUINOLONES IN VARIOUS MEDIA - GROUND-STATE ACID-BASE EQUILIBRIA

The fluorescence emission from fluoroquinolones is shown to be associa ted with the substituted quinoline portion of the molecule. Neutral, a nionic, zwitterionic and cationic forms of the fluorophore are propose d to account for the fluorescent behavior in aqueous and organic media of different acidities. In aqueous solution a ground-state pKa was ob served for NFX and CPFX from a study of the pH vs. fluorescence profil e with excitation at 331nm. The ground-state microscopic dissociation constants for NFX or CPFX were determined, explained the causes of flu orescence changing. The optimum conditions for the fluorimetric determ ination of NFX, CPFX are an acidic medium (pH=2 similar to 4.0) with l ambda(ex)=280nm or 331nm and lambda(em)=445nm.