Spectrofluorimetric and spectrophotometric determination of rosiglitazone maleate in pharmaceutical preparations and biological fluids

Abstract

Two simple, sensitive and specific methods were developed for the determination of rosiglitazone maleate (ROZ) in pure form, pharmaceutical preparations, and biological fluids. Method I (spectrophotometry) is based on complex formation of (ROZ) with both copper(II) chloride, and aluminum (III) chloride in borate buffer (pH 6.5). The absorbance of the formed complexes was measured at 318 nm. The absorbance- concentration plots were rectilinear over the concentration range of 8 – 80 and 5 – 70 μg/ml, with detection limits of 1.98 and 1.32 μg/ml for Cu(II) and Al(III), respectively. Method II is based on the spectrofluorimetric determination of ROZ through complex formation with Al+3 in acetate buffer of pH 5. The relative fluorescence intensity of the formed complex was twice that of the native fluorescence of the drug and was measured at 376 nm after excitation at 318 nm. The fluorescence intensity – concentration plot was rectilinear over the concentration range of 0.03 – 2.0 μg/ml with minimum quantification limit (LOQ) of 0.02 μg/ml and minimum limit of detection (LOD) of 0.01 μg/ml. The factors affecting the complex formation in both methods (I and II) were carefully studied and optimized. Both methods were applied for the determination of ROZ in its tablets. The results obtained were in good agreement with those obtained by the comparison method. Furthermore, method II was applied for the determination of ROZ in spiked and real human plasma, and the mean % recoveries (n = 4) were 97.54 ±0.56, and 97.38±0.93 respectively. The stability of the formed complexes in both methods was studied, and the proposed methods were found to be stability indicating ones. The composition of these complexes as well as their stability constants was also investigated. Moreover, the methods were utilized to investigate the kinetics of alkaline, acidic, and oxidative induced photodegradation of the drug. The apparent first-order rate constant and halflife of the photodegradation products were calculated. Reaction pathways were postulated.