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

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 x 4.6 mm, 5 microm) 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.