Supramolecular interaction of 18‐crown‐6 ether with mesalazine and spectrofluorimetric determination of mesalazine in pharmaceutical formulations

The supramolecular interaction of protonated mesalazine (MSZ) and 18‐crown‐6 ether (18C6) has been examined by Ultraviolet–visible, FT‐IR and fluorescence spectroscopy. The formation of the inclusion complex has been confirmed based on the changes of the spectral properties. The MSZ–18C6 host–guest complex formed in (1:1) stoichiometry and the inclusion constant (K = 1.411 × 10² L mol^–1) was ascertained by the typical double reciprocal plots. Furthermore, the thermodynamic parameters (ΔG°, ΔH° and ΔS°) of (MSZ‐18C6) were obtained. Based on the remarkable enhancement of the fluorescence intensity of MSZ produced through complex formation, a simple, accurate, rapid and highly sensitive spectrofluorometric method for the determination of MSZ in aqueous solution in the presence of 18C6 was developed. The measurement of relative fluorescence intensity was carried with excitation at 298 nm, emission 410 nm. All variables affecting the reactions were studied and optimized. Beer's law was obeyed in the concentration range of 0.1–0.9 µg/mL. The absorbance was found to increase linearly with increasing concentration of MSZ. The molar absorptivity, Sandell sensitivity, limit of detection (LOD) and limit of quantification (LOQ) were calculated. The validity of the described method was assessed, and the method was successfully applied to the determination of MSZ in its pharmaceutical formulation. In addition, a solid inclusion complex was synthesized by the coprecipitation method. Copyright © 2015 John Wiley & Sons, Ltd.