The solution was sonicated for about 20 min and then made up to volume with diluent. Finally 10 mcg/ml of each drug concentration Smad activation solution was prepared. The amount of drug present in pharmaceutical formulation was calculated through the following formula: Cy=(A1/ax1)−CxCy=(A1/ax1)−Cx Cx=((Qm−Qy)/(Qx−Qy))(A1/ax1)Cx=((Qm−Qy)/(Qx−Qy))(A1/ax1)where, Cy is a concentration of nifedipine in mixture; Cx is a concentration of atorvastatin in mixture; Qx (absorption ratio of atorvastatin) = ax2/ax1; Qy (absorption ratio of nifedipine) = ay2 − ay1; Qm (absorption ratio of mixture = A2/A1; A1 is absorption at 297 nm
in mixture; A2 is absorption at 237 nm in mixture and a is an absorptivity. A typical overlap spectrogram INCB018424 of standard atorvastatin calcium and nifedipine
HCl was shown in Fig. 1. The described method has been validated for the assay of atorvastatin Calcium and nifedipine HCl using parameters14 like linearity, precision, ruggedness, accuracy, LOD and LOQ. An absorption ratio method procedure was proposed as a suitable method for the analysis of atorvastatin Calcium and nifedipine HCl in dosage forms. The λmax was found to be 237 nm and 297 nm. The regression equation for the method at 297 nm was found to be y = 0.028x + 0.0117 (r2 = 0.9942) where 0.028 ± 0.0001is a slope; 0.0117 ± 0.0007 is an intercept; r2 is correlation coefficient (0.9942 ± 0.0001) and found to be linear over Beer’s range 6–10 μg/ml respectively. The regression equation for the method at 237 nm was found to be y = 4.515x − 0.0041 (r2 = 0.9999) where 4.515 ± 0.0180 is a slope; −0.0041 ± 0.0028 is an intercept; r2 is correlation coefficient (0.9999 ± 0.00002) and found to be linear over Beer’s range 6–10 μg/ml respectively. The linearity graph was shown in Fig. 2. The percentage of purity of atorvastatin
Calcium and nifedipine HCl in tablet dosage form was 95.80% and 98.94% respectively. The spectrogram of mixtures consist atorvastatin calcium and nifedipine HCl was shown in Fig. 1. The precision of the spectrophotometer system was determined using the %RSD of the absorbance for six replicate injections of the drug. The %RSD Thalidomide was less than 2. In order to verify the accuracy of the described method, recovery studies were carried out by analyzing model mixtures contained 80%, 100% and 120% of sample solution of atorvastatin Calcium and nifedipine HCl and along with 2 μg/ml of bulk standard solution within the linearity ranges. The mean percentage recoveries were found to be 100.45, 99.26 and 100.35%w/w for 80%, 100% and 120% respectively. The percent recoveries values indicate less interference from excipients used in formulation. LOD for atorvastatin Calcium and nifedipine HCl was found to be 0.1028 μg and 0.1214 μg respectively. LOQ for atorvastatin Calcium and nifedipine HCl was found to be 4.464 μg and 0.3678 μg respectively.