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 (q0) and two pseudo first-order quenching compartments (q1 + q2). The q0 values had a positive relationship with temperature, while (q1 + q2) were negatively related with temperature. In addition, OFL–DOM binding quantified by (q1 + q2) was consistent with binding result obtained from dialysis equilibrium system. We concluded that q0 was resulted from dynamic quenching, while (q1 + q2) 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.

► Pseudo first-order two-compartment kinetic model fitted the kinetics data well.
► Dynamic quenching and static quenching were identified in the model.
► Two static quenching compartments have rate constants differed 10 times.
► Dynamic quenching accounted for 30–90% of the overall quenching.