Study on the inclusion complex between beta-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 beta-cyclodextrin (beta-CD) has been studied by spectrofluorimetry. The results showed that beta-CD reacted with celecoxib to form an inclusion complex. 1:1 stoichiometry for beta-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 beta-CD. The thermodynamic parameters (DeltaH degrees, DeltaS degrees and DeltaG degrees) 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 beta-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 microg 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.