Study on the inclusion complex between β-cyclodextrin and celecoxib by spectrofluorimetry and its analytical application

The supramolecular interaction of celecoxib (chemically 4-[5-(4-methylphenyl)-3-(trifluoromethyl)-1H-pyrazol-1-yl] benzene sulfonamide) and β-cyclodextrin (β-CD) has been studied by spectrofluorimetry. The results showed that β-CD reacted with celecoxib to form an inclusion complex. 1:1 stoichiometry for β-CD-celecoxib complex was established and its association constant at different temperatures was calculated by applying a non-linear regression method to the change in the fluorescence of celecoxib that brought about by the presence of β-CD. The thermodynamic parameters (ΔH°, ΔS° and ΔG°) associated with the inclusion process were also determined. Based on the significant enhancement of the fluorescence intensity of celecoxib produced through complex formation, a simple, rapid and highly sensitive spectrofluorimetric method for the determination of celecoxib in aqueous solution in the presence of β-CD was developed. The measurement of relative fluorescence intensity was carried out at 390 nm with excitation at 270 nm. A linear relationship between the fluorescence intensity and celecoxib concentration was obtained in the range of 0.1–4.0 μg ml^–1, with a correlation coefficient of 0.9996. The detection limit was 7.29 ng ml^–1 and the relative standard deviation was 1.28%. The method was successfully applied to the determination of celecoxib in pharmaceutical preparations.