Dihydrogen Phosphate Solution pH Research Articles

RAPID AND SENSITIVE DETERMINATION OF KETOPROFEN IN MICRO-WHOLE BLOOD SAMPLES BY HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY AND ITS APPLICATION IN A PHARMACOKINETIC STUDY IN RATS

A new simple and sensitive method for determination of ketoprofen in micro-whole blood samples was developed, and its usefulness was demonstrated by the characterization of the oral pharmacokinetics of this drug in rats. Whole blood samples were added with perchloric acid to precipitate proteins, and supernatant was injected into the chromatographic system. Separation of compounds was achieved with a Symmetry C18 column eluted with a mixture of acetonitrile and 0.1 M potassium dihydrogen phosphate solution pH 3.5 (48:52 v/v) as the mobile phase at flow rate of 1.0 mL/min. Detection was carried out by absorbance at 260 nm. Under these conditions the method was linear in the range 0.1–15 µg/mL. In order to demonstrate the usefulness of this method, oral pharmacokinetics of ketoprofen after administration of 1, 3.2, and 10 mg/kg was evaluated in rats. Blood samples were obtained at selected times during 24 hr and successfully analyzed by the method described. It is concluded that the method is suitable for pharmacokinetic studies of ketoprofen using small volume of sample.

Liquid chromatographic analysis of oxytocin and its related substances

A selective gradient liquid chromatographic (LC) method for the determination of oxytocin (OT) and its related substances in bulk drugs has been developed. The method uses a reversed-phase C18 column (25 cm × 4.0 mm i.d.), 5 μm kept at 40 °C. The mobile phases consist of acetonitrile, dihydrogen phosphate solution pH 4.4 and water. The flow rate is 1.0 ml/min. UV detection is performed at 220 nm. A system suitability test (SST) was developed to govern the quality of the separation. The separation towards OT components was investigated on different C18 columns. The developed method was further validated with respect to robustness, precision, sensitivity and linearity. A central composite design was applied to examine the robustness of the method. The method shows good precision, sensitivity, linearity and robustness. Two commercial OT samples were examined using this method. Furthermore, the method proved to be successful when applied to analyze a marketed OT formulation for injection.