SPECTROFLUOROMETRIC STUDY OF THE ACID-BASE EQUILIBRIA AND COMPLEXATION BEHAVIOR OF THE FLUOROQUINOLONE ANTIBIOTICS OFLOXACIN, NORFLOXACIN, CIPROFLOXACIN AND PEFLOXACIN IN AQUEOUS-SOLUTION

A spectrofluorimetric study of the acid-base properties and cf the com plexation behavior of the fluoroquinolone antibiotics ofloxacin (OF), norfloxacin (NOR), ciprofloxacin (CIP) and pefloxacin (PEF) has been p erformed. Their dissociation constants were determined by a combined p otentiometric/fluorimetric technique. All studied fluoroquinolones for m fluorescent complexes with Sc3+ in slightly acidic solutions (pH=4.2 , lambda(ex)similar to 280 nm, lambda(em)similar to 430 nm (480 nm for OF). A simple, rapid and sensitive spectrofluorimetric method based o n the formation of scandium complexes has been developed for the deter mination of OF, NOR, CIP and PEF in aqueous solutions. Calibration gra phs for all four fluoroquinolones were linear up to 1.0 mu M, with res ults having a mean relative error of 3.2%. The 3 sigma detection limit s are 1.1, 0.6, 0.5 and 1.0 nM for OF NOR, CIP and PEF, respectively. The method has been successfully!. applied to the determination of NOR in synthetic serum samples (5.0-50.0 mu M) after deproteinization wit h acetonitrile (serum-acetonitrile, 1:2 v/v) with a mean recovery of 9 3.4+/-1.1% (n=3). (C) 1997 Elsevier Science B.V.