Interaction and fluorescence quenching study of levofloxacin with divalent toxic metal ions

Abstract

The binding interaction of levofloxacin (LF) with toxic metal ions Cd+2, Hg+2 and Pb+2 was
investigated in aqueous acidic medium by absorption and fluorescence spectrophotometry. The
experimental results showed that the metal ions quench the fluorescence intensity of LF by forming
LF2 -metal complex. It was found that static quenching was the main reason of fluorescence
quenching. Quenching of LF by toxic metal follows the order Hg>Cd>Pb. The stoichiometry and logK
of formed chelate was determined by absorption and fluorescence spectrophotometry. The quenching
constant Ksv and the binding sites “n” were determined together with their thermodynamic parameters
at 25 ºC and 35 ºC. The positive entropy change indicated the gain in configurational entropy as a
result of chelation. The process of interaction was spontaneous and mainly ∆S-driven.