Separation of the Components of Extra-Strength Excedrin I: Acid-Base Extraction

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Separation of the components of Extra-Strength Excedrin I: Acid-Base extraction Introduction The purpose of this experiment is to analyze the purity of Extra-Strength Excedrin® by utilizing thin-layer chromatography and determine the percent recoveries of its components. Three active ingredients will be extracted and collected from two tablets of Extra-Strength Excedrin® by utilizing acid-base extraction method. Three active ingredients of Extra-Strength Excedrin® are acetylsalicylic acid(aspirin), acetaminophen and caffeine, and their structures are: In addition, there is a binding material, which binds other three components together. These compounds can be separated by acid-base extraction because of their different acidities. A binding material can be separated by dissolving the tablet in ether since three active ingredients are soluble. Then, aqueous K2HPO4 and KOH are used to extract the ether solution with the conjugate base of the Aspirin layer and the conjugate base of the Acetaminophen, respectively. The caffeine can be isolated from the left over layer by evaporating the ether. Two separated solutions form solid by acidifying with HCl and the solid residue can be collected by vacuum filtration. According to the Revell's lab experiment, aspirin, acetaminophen, caffeine recoveries are 60% or higher, <10% and <5%, respectively. The reason for such a low percent recoveries for acetaminophen is due to a formed solid is too fine to be filtered, and for caffeine is due to its low solubility in diethyl ether(1.8mg/ml) than in water (22mg/ml). Not only caffeine's solubility in water can affect its percent recoveries, but also it can affect other two compounds by contaminating with caffeine. For the TLC, expected approximate Rf values for aspirin, acetaminophen, and caffeine are 0.6, 0.3, and 0.1 , respectively. Procedures A.

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