Stability indicating isocratic rp-hplc method for simultaneous estimation of amlodipine and valsartan in pharmaceutical solid dosage form

A RP-HPLC isocratic method for simultaneous estimation of valsartan and amlodipine in pharmaceutical solid dosage preparations i.e. in tablets, capsules and powders has been developed and val-idated. The chromatographic analysis was performed on a 5 μm particle C-18 (Zorbax Eclipse Plus, USA) column (4.6 × 150 mm) and evaluated the system suitability through theoretical plates (N), tailing factor (T) and %RSD. Acetonitrile and water (1:1) were used as diluents. The mobile phase, methanol:acetoni-trile: solution A (30:30:40, v/v/v) at a flow rate of 1.5 mL/min was used. UV detection was performed at 237 nm and peak was identified with a retention time as compared with standard. The limit of detection of amlodipine and valsartan was 0.35 μg/mL and 5.42 μg/mL, respectively, while the limit of quantification was 1.05 μg/mL and 16.42 μg/mL, respectively. The proposed method was found to be linear from 8.0 to 40 μg/mL for amlodipine having a correlation coefficient of 0. 9999. For valsartan, the method was found to be linear from 80.0 to 400 μg/mL having correlation coefficient 0.9999. The samples were also studied for accelerated (40 ± 2 °C/75% ± 5%) and long-term storage conditions (30 ± 2 °C/65% ± 5%) for 6 months. The recovery was found between 98.80%-102.84% for both amlodipine and valsartan from tablet formulation and no interference peaks were found during stability study. The method was validated as per ICH guideline and found beneficial for routine analysis and simultaneous estimation of amlodipine and valsartan in the pharmaceutical solid dosage form.