Spectrofluorimetric determination of nalidixic acid based on host–guest complexation with γ-cyclodextrin

Abstract

The characteristics of host–guest complexation between γ-cyclodextrin and nalidixic acid were investigated by fluorescence spectrometry. A 1 : 1 stoichiometry of the complex was established and an association constant of 292 l mol^–1 was calculated by using the changes in the fluorescence of nalidixic acid that occurred when it was included in the hydrophobic cyclodextrin cavity. A spectrofluorimetric method for the determination of nalidixic acid was developed, with a range of application between 0.1 and 2 µg ml^–1. The method was applied satisfactorily to the determination of nalidixic acid in a pharmaceutical preparation and in urine.