Determination of Heparin Using Ciprofloxacin-Tb³⁺ as a Fluorescence Probe

Abstract

A new spectrofluorometric method was developed for the determination of trace amounts of heparin (Hep). Using ciprofloxacin (CIP)-terbium (Tb³⁺) as a fluorescent probe, in a buffer solution of pH 7.20, Hep can remarkably enhance the fluorescence intensity of the CIP-Tb³⁺ complex at λ = 545 nm; also, the enhanced fluorescence intensity the Tb³⁺ ion is proportional to the concentration of Hep. The optimum conditions for the determination of Hep were also investigated. The dynamic range for the determination of Hep is 0.1 - 1.2 µg ml^-1 with a detection limit of 6.89 ng ml^-1. 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 and binding numbers of heparin with the probe are 2.44 × 10⁵ l mol^-1 and 19.7. Moreover, the enhancement mechanisms of the fluorescence intensity in the CIP-Tb³⁺ system and the CIP-Tb³⁺-Hep system have also been considered.