Thin-Layer Chromatography of Analgesis Drugs

TLC OF ANALGESIS DRUGS

Introduction:

This was an experiment of a thin-layer chromatography (TLC) used to determine the composition of various over-the-counter analgesics. Chromatography is a technique used to separate and identify individual components in a mixture. Adsorption chromatography was a technique makes used of the fact that components of a mixture tended to move at different speeds due to the differing attractions of the components to the coating material compared to the tendency of the components to remain in the moving fluid. During the elution with the solvent, the sample was partition itself between the stationary phase -the adsorbent layer; and the moving phase- the solvent so that the distance which the sample moves up the plate was characteristic of that substance and would differ from one substance to the next. Separation of a mixture into the component parts was achieved by elution with solvents of different polarity. The principles of polarity and of intermolecular attractions were of importance in determining how compounds would behave during the separation. While the more polar components of a mixture would stick more strongly to the polar stationary phase and thus, move slower, the least polar components would move the fastest and run higher up the plate. A mixture of 95% ethyl acetate and 5% acetic acid was used as the solvent for the chromatogram. The best known of substance that relieves pain is aspirin, but several other chemically similar compounds were also used as analgesics. The reference compounds were used: Caffeine, aspirin, ibuprofen and NoDoZ... Caffeine is sometime added to these formulations to overcome drowsiness. For cold remedies and decongestants aspirin and caffeine are primary ingredients. In addition to the active ingredients, the tablets of these drugs contain starch, lactose, and other substances that act as binders and permit rapid solution, and sometimes also inorganic bases.

C8H10N4O2 C9H8O4 C13H18O2

Caffeine Aspirin Ibuprofen

NoDoz is brand name of caffeine. It is used to help stay awake and to increase alertness. It is also used in combination with pain relievers to enhance the effectiveness in treating headaches.

After the plate has been developed, it is examined under ultraviolet (UV) light to note the location of the spots; and placed the plate into iodine jar to helped more visible. The solvent system used to dissolve the compounds, the adsorbent coated onto the TLC plate, the thickness of the adsorbent layer, and the relative amount of the material spotted onto the plate.

The distance moved by the spot of sample divided by the distance moved by the solvent is known as the Rf value and was characteristic of that compound for the solvent system was used. A mixture of substances would give rise to a series of spots, one corresponding to each component.

Rf = Distance traveled by substance (A)

Distance traveled by the solvent front(C)

Rf value is constant for any given compound, and it corresponds to a physical property of that compound.

Procedure:

Analgesic