Development and validation of a liquid chromatographic method for the determination of trandolapril and verapamil in capsules

The development and validation of an isocratic high performance liquid chromatographic procedure for the determination of trandolapril and verapamil in capsules is reported. The drugs were analysed on a LiChrosorb RP18 column with a mobile phase composed of acetonitrile -methanol-phosphate buffer pH 2.7 (40:30:20) and UV detection at 220 nm. Peak height ratios were linearly related to amounts of the drugs in the range 3-20 mug/mL. The inter-day precision (CV) obtained for the standard solutions ranged from 0.40 to 2.18% for trandolapril and from 0.35 to 2.57% for verapamil. The inter-day coefficients of variation for replicate analyses in capsules ranged from 0.5 to 2.49% for trandolapril and from 0.33 to 1.61% for verapamil. The recovery of analytes after extraction from formulations using the described method, was 99.94 +/- 1.69% and 98.13 +/- 1.20% (mean +/- SD) for trandolapril and verapamil, respectively.