Background Simultaneous spectrophotometric determination of samples containing more than one analyte presents analytical challenge; the choice of an analytical procedure is strictly related to the extent of overlapping between the individual absorption peaks of these components; if the absorption peaks are satisfactorily resolved, the determination is not problematic, but if the individual component signals are partly or totally overlapped, then powerful techniques are needed. Combined amlodipine and atorvastatin are typical example where special techniques are needed to resolve bands overlapping. Results Application of multiwavelength regression and absorbance factor methods to the analysis of atorvastatin and amlodipine combination proved to be satisfactorily capable of accurate and precise determination of the two analytes. The two methods recoveries were very close to the expected analytes concentrations, and the precision of the methods was < 2% relative standard deviation. Statistical comparison indicated that there is no significant difference between the assay results obtained by the two method as the calculated t values 0.91 and 1.13 for amlodipine and atorvastatin, respectively, were less than the tabulated t value 2.23 at 95% confidence level. Conclusion The proposed methods are accurate, precise, simple and inexpensive. They can be applied successfully to the analysis of the two drugs in combined dosage form.
Background Chromatographic separation of polar and nonpolar compounds when presented in combined dosage forms has always been considered as great analytical challenge. Separation and retention of both polar and nonpolar compounds by the same stationary phase can be a useful approach for analyses of complex samples with such a difference in chemical properties. Loratadine (nonpolar) and pseudoephedrine (polar) are typical examples of this situation. Results The Box–Behnken design was used to optimize the separation process, an efficient separation of loratadine and pseudoephedrine was achieved within 6 min; employing a mixture of 16.0 mM ammonium acetate buffer (pH 4.5) and acetonitrile (23:77, v/v) as isocratic mobile phase, pumped at 1.0 mL/min through a Zorbax cyanopropyl column (250 mm × 4.6 mm, 5 μm), the analytes were detected at 250 nm. Under the same conditions, separation of sodium benzoate preservative co-formulated with the two analytes in syrup formulation was also achieved. The calibration curve demonstrated excellent linearity in the range of 24.6–123.2 μg/mL and 594.8–2974.0 μg/mL for loratadine and pseudoephedrine, respectively with determination coefficient (r2) > 0.999. Conclusion The method’s accuracy bias < 2.0%, repeatability and intermediate precision (%RSD < 2.0%) were verified. In addition, system suitability parameters were found within the acceptable limits. Satisfactory results were obtained upon the application of the validated method to the analysis of commercial tablet and syrup formulations.
A simple, accurate and precise UV-spectrophotometric method based inverse least-squares was developed for the simultaneous determination of atorvastatin and amlodipine in tablet formulation. The absorbance values of the two analytes were linear with the concentration at the wavelengths taken at 5 nm interval over the range of 230 -260 nm. The calibration equations were developed using the absorbance values of nine synthetic mixtures containing different concentrations of two analytes measured at 5 nm intervalsin the range of 230 -260 nm. The developed equations werethen validated by calculating the analytes recovery from the analysis of a set of another five synthetic mixtures, the mean% recoveries were 100.02% and 100.06% with the corresponding% RSD of ±0.36 and±0.51 for atorvastatin and amlodipine, respectively. The calibration equations obtained were then used to obtain the concentration of each analyte in commercial samples. The mean % recoveries were 100.43% and 100.28% with the corresponding% RSD of ±0.78 and±0.85 for atorvastatin and amlodipine, respectively. The validity of the proposed method was confirmed through the statistical comparison of the obtained results with those obtained by a reference method utilizing high performance liquid chromatography for the determination of the two actives, the calculated t-values at (P=0.05, n =6) were 1.47 and 0.73 compared to the tabulated value of 2.23.
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