Determination of flufenamic and mefenamic acids in pharmaceutical preparations using organized media

The fluorescence properties of flufenamic (FF) and mefenamic (MF) acids were obtained in aqueous and binary aqueous-organic solvents with and without alpha- and beta-cyclodextrins (CDs). In addition, the spectral behaviour of the model compounds in aqueous micellar systems of ionic and non-ionic surfactants were investigated. It was shown that, in aqueous acidic solutions, the investigated analytes were better incorporated in CDs (FF) and micelles (FF and MF). The luminescence emissions from the analytes were found to be greatly enhanced by surfactants. The fluorescence of analyte-surfactant system was quenched by increasing amounts of organic solvents. The changes in the dissociation constants of FF and MF in solutions of anionic and non-ionic surfactants (sodium dodecyl sulfate (SDS) and Triton X-100, respectively) were studied spectrofluorimetrically. The fluorescence intensity enhancements in CDs media relative to aqueous solution ranged from 1.3 to 1.6. Sensitive micellar-enhanced spectrofluorimetric methods for the determination of FF and MF were developed, with ranges of application down to ng ml(-1) level. The linear dynamic ranges and relative standard deviations were reported. The methods were applied satisfactorily to the determination of both compounds in pharmaceutical preparations with recoveries of 98-101%. (C) 1998 Elsevier Science B.V.