title: Subcritical water extraction and determination of nifedipine in pharmaceutical formulations.
abstract: A rapid and simple continuous method for the extraction of nifedipine from tablets was developed by using pressurized hot water at 150 degrees C. This is the first time that subcritical water was applied to the extraction of low-polarity compounds in pharmaceutical analysis. The method is based on the increment in solubility of nifedipine in subcritical water. Extraction temperature and static and dynamic extraction time were optimized in order to reach quantitative extraction of the drug from the tablets. After extraction, the drug was determined by spectrophotometry by measuring absorbance at 338 nm. Accuracy and precision of the method were determined by analysis of 10 synthetic samples of pharmaceutical formulations prepared with common tablet excipients. Recovery was found to be 99.2% with a relative standard deviation of 1.9%, which indicates that the excipients of the formulation do not interfere in the determination. The method was applied to the determination of the drug content uniformity in tablets.
authors.affiliation: Universidad de Chile, Facultad de Ciencias Químicas y Farmacéuticas, Departamento de Quimica Inorgánica y Analítica, PO Box 233, Santiago, Chile. prichter@ciq.uchile.cl
authors.forename: Pablo
authors.initials: P
authors.lastname: Richter
authors.forename: Maria Ines
authors.initials: MI
authors.lastname: Toral
authors.forename: Carla
authors.initials: C
authors.lastname: Toledo
mesh_terms: D002121:Calcium Channel Blockers / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid; D020374:Chromatography, Micellar Electrokinetic Capillary; D017022:Flow Injection Analysis; D007202:Indicators and Reagents; D009543:Nifedipine / Q000032:analysis*; D011048:Polarography; D013607:Tablets; D013696:Temperature; D014867:Water / Q000032:analysis
chemical_list: D002121:Calcium Channel Blockers; D007202:Indicators and Reagents; D013607:Tablets; D014867:Water; D009543:Nifedipine