Spectrofluorimetric and micelle-enhanced spectrofluorimetric methods for determination of Felodipine and Nimodipine in pharmaceutical preparations and human plasma.

Rapid, simple and sensitive two spectrofluorimetric methods have been developed for determination of Felodipine (FLD) and Nimodipine (NDP). The first method is based on measuring the native fluorescence of either Felodipine or Nimodipine at 426 nm after excitation at 385 nm. The fluorescence intensity-concentration plots of Felodipine and Nimodipine were rectilinear over the concentration ranges (0.2-3.0) and (0.5-4.0) μg ml(-1), respectively. The second method is based on measuring the fluorescence intensity of the studied drugs in micellar media (0.3% Tween-80) at λex=385 nm and λem=423 nm. In the presence of 0.3% Tween-80, about 1.6-fold and 2.1-fold enhancement can be achieved in the relative fluorescence intensity (RFI) of Felodipine and Nimodipine, respectively. The fluorescence intensity-concentration plots of Felodipine and Nimodipine with Tween-80 were rectilinear over the concentration ranges (0.05-4.0) and (0.1-4.0) μg ml(-1), respectively with determination coefficients (r(2)) of 0.9981 and 0.9990, and limit of quantitation of 0.05 and 0.027μg ml(-1) for FLD and NDP, respectively. The proposed methods were validated according to ICH guidelines and have been successfully applied to the analysis of these drugs in their commercial tablets with high accuracy (97.6-98.8±0.50-1.42%, n=5). The high sensitivity of micellar method permits its application for determination of the cited drugs in spiked human plasma with % recovery (91.9-106.6±0.66-1.7%, n=6).