Spectrofluorimetric determination of trace heparin using lomefloxacin-terbium probe

A new spectrofluorimetric method was developed for determination of trace amount of heparin (Hep). Using lomefloxacin (LOM)-terbium ion (Tb3+) as a fluorescent probe, in the buffer solution of pH 8.70, Hep can remarkably enhance the fluorescence intensity of the LOM-Tb3+ complex at lambda = 545 nm and the enhanced fluorescence intensity of Tb3+ ion is in proportion to the concentration of Hep. Optimum conditions for the determination of Hep were also investigated. The linear range for the determination of Hep was 0.6-2.0 microg/ml and the detection limit was 45.22 ng/ml. This method is simple, practical and relatively free of interference from coexisting substances and can be successfully applied to assess Hep in biological samples. By the Rosenthanl graphic method, the association constant of Hep with the probe is 4.56 x 10(4) l/mol and binding numbers is 18.2. Moreover, the enhancement mechanism of the fluorescence intensity in the LOM-Tb3+ system and the LOM-Tb3+-Hep system have also been discussed.