Abstract:
Four methods were developed for simultaneous determination of metoprolol and felodipine without previous separation. In the first method both drugs were determined using first derivative UV spectrophotometry, with zero crossing measurement at 222 and 235 nm for metoprolol and felodipine, respectively. The second method depends on first derivative of the ratios spectra by measurements of the amplitudes at 250.1 nm for metoprolol and 224.3 nm for felodipine. Calibration graphs are established in the range of 20-150 ?g/ml and 10-60 ?g/ml for metoprolol and felodipine, respectively. The third method describes the use of multivariate spectrophotometric calibration for the simultaneous determination of the analyzed binary mixture where the resolution is accomplished by using partial least squares (PLS) regression analysis. Although the components show high degree of spectral overlap, they are simultaneously determined with high accuracy and without interference of pharmaceutical dosage form excipients. A comparison with the related multivariate method of classicial least squares (CLS) analysis is done showing less relative results due to severe spectral overlap of the studied drugs. In the fourth method (HPLC), a reversed-phase column and a mobile phase of methanol:water:acetonitrile (70:22:8 v/v/v/) at 0.9 ml/ min flow rate is used to separate both drugs and UV detection at 260 nm. Good linearities are obtained in concentration range of 0.15-15 ?g/ml for metoprolol and 0.03-5 ?g/ml for felodipine. All the proposed methods are extensively validated. They have the advantage of being economic and time saving. All the described methods can be readily utilized for the analysis of pharmaceutical formulations, the fourth method (HPLC) is successfully applied for the analysis of both drugs in human serum samples. The results obtained by adopting the proposed methods are statistically analyzed and compared with those obtained by reported methods. � 2007 Science Publications.
