Abstract
A highly sensitive spectrofluorometric method was developed for the determination of verapamil hydrochloride (VP HCl) in pharmaceutical formulations and biological fluids. The proposed method is based on investigation of the fluorescence spectral behavior of VP HCl in micellar systems, such as sodium dodecyl sulfate (SDS) and β-cyclodextrin (β-CD). In aqueous solutions of borate buffer of pH 9 and 8.5, VP HCl was well incorporated into SDS and β-CD, respectively, with enhancement of its native fluorescence. The fluorescence was measured at 318 nm after excitation at 231 nm. The fluorescence intensity enhancements were 183 and 107% in SDS and in β-CD, respectively. The fluorescence-concentration plots were rectilinear over the range of 0.020.2 and 0.020.25 μg/mL, with lower detection limits of 5.58 × 103 and 3.62 × 103 μg/mL in SDS and β-CD, respectively. The method was successfully applied to the analysis of commercial tablets and the results were in good agreement with those obtained with the official method. The method was further applied to the determination of VP HCl in real and spiked human plasma. The mean % recoveries in the case of spiked human plasma (n 4) was 92.59 3.11 and 88.35 2.55 using SDS and β-CD, respectively, while that in real human plasma (n 3) was 90.17 6.93 and 89.17 6.50 using SDS and β-CD, respectively. The application of the method was extended to the stability studies of VP HCl after exposureto ultraviolet radiation and upon oxidation with hydrogen peroxide.
Thermal Analysis Applied to Verapamil Hydrochloride Characterization in Pharmaceutical Formulations