Sensitive and simple liquid chromatographic method with ultraviolet detection for the determination of nifedipine in canine plasma

An isocratic high-performance liquid chromatographic method with detection at 240 nm was developed, optimized and validated for the determination of nifedipine in canine plasma. Liquid–liquid extraction was used as the sample preparation technique. Carbamazepine was used as internal standard. A Hypersil BDS RP-C18 column (250 mm × 4.6 mm, 5 μm) was equilibrated with a mobile phase composed of water and methanol, 45:55 (v/v). Its flow rate was 1 ml min−1. The elution time for nifedipine and carbamazepine was approximately 12 and 8 min, respectively. Calibration curves of nifedipine in plasma were linear in the concentration range of 1–200 ng ml−1. Limits of detection and quantification in plasma were 0.5 and 1.5 ng ml−1, respectively. Recovery was greater than 98%. Intra- and inter-day relative standard deviation for nifedipine in plasma was less than 8.5 and 10%, respectively. This method was applied to the determination of nifedipine plasma levels after administration of commercially available soft gelatine capsules to dogs.