Chromatography of Commercial Analgesics

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Chromatography of Commercial Analgesics

Using the thin layer chromatography the major components of a commercial analgesic tablet will be indentified and purified. The active ingredients of the analgesic used were characterized by comparison with chromatograms of aspirin, acetaminophen, ibuprofen, mefanemic acid, and caffeine through the use of UV chromatography then the Rf value was calculated for each solvent.

In this experiment, thin-layer chromatography (TLC) will be used to determine the composition of various analgesics. Chromatography is a technique used to separate and identify individual components in a mixture. Chromatographic techniques make use of the fact that components of a mixture tend to move at different speeds along a coated tube or flat surface.

Thin-layer chromatography is one of the easiest of the many chromatographic techniques. A thin layer of a suitable solid substance is coated on a sheet of glass or plastic. A very small sample of the mixture to be analyzed is “spotted” onto the sheet. By immersing one edge of the sheet in an appropriate liquid developing solvent, the solvent is drawn up the sheet by capillary action, and the compounds of interest are carried along at different rates, effectively separating the components. This is commonly called “developing” the plate. After the plate has been developed, it is examined under ultraviolet (UV) light, which allows you to note the location of the spots.

TLC include 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. Under an established set of experimental conditions, a given compound always travels a fixed distance relative to the distance the solvent front travels. This ratio of the distance the compound travels to the distance the solvent front travels is called the Rf value.

Rf = distance traveled by the...
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