Separation and Identification of the Major Components of Common over-the-Counter Painkilling Drugs

Topics: Acetic acid, Solvent, Carboxylic acid Pages: 6 (1371 words) Published: November 20, 2011
Title: Separation and Identification of the major components of common over-the-counter painkilling drugs

Purpose: 1.To separate acetaminophen, aspirin and caffeine from painkilling drugs.
2.To determine the melting points of acetaminophen, aspirin and caffeine
3.To identify the separated components(acetaminophen, aspirin and caffeine) by thin-layer chromatography

Apparatus and Reagents Used :
1.4:1 (v/v) 1-Butyl ethanoate/ethanoic acid
2.3M Sodium hydroxide solution
3.3M Hydrochloric acid
7.Anhydrous MgSO4
8.Mortar and pestle
10.Capillary tubes(Melting-point tubes)
11.TLC plates
12.Painkilling tablets
13.pH papers
14.Test tubes
15.Conical flasks
16.TLC Chamber
17.Separating funnel
18.Melting-point apparatus

Binders, for instance, starch, microcrystalline cellulose and silica gel, which are commonly found in the painkilling tablets and used to prevent the components from crumbling on storage or while being swallowed, are all insoluble in water and common organic solvents such as dichloromethane and ethanol. Solubility is one of the crucial concepts needed in order to separate the three components – acetaminophen, aspirin and caffeine in the painkilling tablet. Aspirin with a binder and caffeine are soluble in dichloromethane while acetaminophen is not. The two main components aspirin and caffeine could be extracted when dissolving in the dichloromethane, followed by filtration. Subsequently, using the same concept, acetaminophen which dissolves in ethanol can be extracted from the binder. Solubility could be a means to separate them because conjugated base and acid which dissolve in water but not dichloromethane are formed after aspirin and caffeine react and extract with base. The aspirin in the form of a water-soluble salt can be separated by simple filtration due to the immiscibility between water and dichloromethane. For the identification of those products obtained, melting-point determination and thin-layer chromatography is carried out. Thin-layer chromatography could act as a useful means of quickly characterizing the main active ingredients of aspirin, caffeine and acetaminophen when they do not have many other organic compounds in significant proportions. Compared with different Rf values of each other, the interrelationship among them could be found. That is a test checking whether there are any same components among the 3 commercial analgesics. Procedures:

A.Separation of acetaminophen/binder from aspirin/caffeine
1.The given tablets were grinded to very fine powder in a mortar. 2.This powder was placed in a conical flask with adding 10cm3 of dichloromethane. 3.The conical flask was put into a beaker of warm water at 30 oC. 4.The solution was filtrated.

B. Separation of aspirin and caffeine
1.The filtrate obtained in Part(A) was transferred into a separating funnel. 2. 8 cm3 of 3M sodium hydroxide solution was added and the mixture was shaked thoroughly.
3.The aqueous layer was removed and the organic solution was extracted again with 1 cm3 of water.
4.The aqueous layer was extracted and combined the layer with the previously collected aqueous extract. C. Extraction and isolation of aspirin
1. 20 drops of 3M hydrochloric acid was added drop by drop to the aqueous hydroxide extract obtained in Part(B) with testing the acidity of the extract with pH paper from time to time until the pH of the extract was nearly 3.

2.The mixture was cooled with an ice-bath if a suspension was formed.
3.The mixture was then filtered and the solid was washed with iced water.
4.The solid was then dried completely.
5.The solid obtained was weighed.
D. Extraction and isolation of acetaminophen
1.The solid residue obtained in Part(A)was transferred to a conical flask.
2.8 cm3 of ethanol was added and the mixture was boiled for 2 minutes.
3.The mixture was filtered.
4.the filtrate was...
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