Determination of felodipine in biological fluids
Aim. Development of methods for the determination of felodipine in blood and plasma. Methods. The study object was felodipine [3-ethyl-5-methyl-4-(2,3-dichlorophenyl)-2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylate]. The experiments were carried out on model mixtures of felodipine with blood and human blood plasma. Acetone was proposed as an isolating agent for the extraction of felodipine from biological fluids. To identify and quantify felodipine in extracts from blood and plasma, the methods of thin-layer chromatography, spectrophotometry and gas-liquid chromatography in combination with mass spectrometry were proposed. Results. The possibility of using acetone as an isolating agent to extract felodipine from biological fluids is demonstrated. The optimal conditions for the extraction of felodipine with acetone were found to be achieved already at 2-fold infusion of a biological object with an isolating agent, if the mass ratio of isolating liquid and biological material at each infusion stage is at least 2:1, and the infusion time is at least 30 minutes. Optimal felodipine purification conditions were achieved in a macrocolumn (15×1 cm) of Silasorb S-18 sorbent of 30 μm with elution of the substance with the polar eluent acetonitrile-water (7:3). The methods of determining felodipine in the blood and plasma were developed. With the content of felodipine of 25 mg in 25 g of biological fluid, the developed methods allow determining 86.01-87.86% in blood and 95.64-96.18% of the substance in blood plasma. The values of the detection limit of felodipine in the blood and plasma by the developed methods are 200 μg/100 g and 150 μg/100 g, respectively. Conclusion. Methods for the determination of felodipine in biological fluids were developed based on isolating with acetone and purification in the Silasorb S-18 sorbent column; use of these methods allows determining up to 87.86% of the analyte in the blood and up to 96.18% in the blood plasma.