Spectrofluorimetric determination of carvedilol in dosage form and spiked human plasma through derivatization with 1-dimethylaminonaphthalene-5-sulphonyl chloride

A sensitive, simple and selective spectrofluorimetric method was developed for the determination of carvedilol (CA) in pharmaceutical formulation and a biological fluid. The method is based on the reaction between the drug and 1-dimethylaminonaphthalene-5-sulphonyl chloride (dansyl chloride) in the presence of mixture (acetone:0.5 M sodium carbonate, 3:2) at pH 10 to yield a highly fluorescent derivative that is measured at 445 nm after excitation at 350 nm. Different experimental parameters affecting the development and stability of the reaction product were carefully studied and optimized. The fluorescence concentration plot was rectilinear over the range of 5.0-80.0 ng ml -1 with a lower detection limit (LOD) of 1.90 ng ml -1 and the limit of quantitation (LOQ) of 5.15 ng ml -1 . Quantum yield, formation constant (K) and free energy change (ΔG) values were calculated. The proposed method was successfully applied to the analysis of commercial tablets. The results obtained were in good agreement with those obtained using the official titrimetric method [1,2]. Furthermore, the method was applied for the determination of CA in spiked human plasma, the mean % recovery (n = 5) is 97.82±0.373. A proposal of the reaction pathway was presented.