Quantitative identification of dynamic and static quenching of ofloxacin by dissolved organic matter using temperature-dependent kinetic approach.

Ofloxacin (OFL) was used as a model antibiotic and the quenching of OFL fluorescence by DOM was examined with an emphasis on temperature-dependent quenching kinetics. OFL fluorescence intensity was corrected for inner filter and temperature effects. The kinetics data were fitted well using a two-compartment pseudo first-order kinetics model. Three quenching compartments were identified using this model, namely, a very fast quenching compartment (q(0)) and two pseudo first-order quenching compartments (q(1) + q(2)). The q(0) values had a positive relationship with temperature, while (q(1) + q(2)) were negatively related with temperature. In addition, OFL-DOM binding quantified by (q(1) + q(2)) was consistent with binding result obtained from dialysis equilibrium system. We concluded that q(0) was resulted from dynamic quenching, while (q(1) + q(2)) was attributed to static quenching. The dynamic quenching of OFL by DOM accounted for 30-90% to the overall quenching and thus was very significant.