Thin Layer Chromatography Lab Report
Thin Layer Chromatography or TLC is a technique used as a separation and identification technique. There are many forms of chromatography, but one thing that remains constant throughout all of the types of chromatography is that there is a stationary phase and a mobile phase. In the case of TLC the stationary phase is the silica gel on the TLC tray.
Chromatograph method is a method of separating mixtures of two or more compounds. Two phases are important in this method; one that is stationary and one that is moving. Chromatography works on the principle that different compounds will have different solubilities and adsorption to the two different phases between which are to be partitioned. Thin Layer Chromatography (TLC) is a solid-liquid technique. The mixture is observed when it is in two different phase; a solid (stationary phase) and a liquid (moving phase). Thin Layer Chromatography (TLC) is a technique which is sensitive, cheap and fast. A thin layer chromatograph plate is used to identify drug component under UV. It is used to support the identity of a compound in a mixture when the Rf of a compound is compared with the Rf of a known compound.
Sample | Distance between start line and spot | Distance between start line and front line | Rf | Aspirin | 3.1 cm | 3.4 cm | 0.912 | Caffeine | 0.7 cm | 3.4 cm | 0.206 | Unknown X1)Unknown Component 12)Unknown Component 2 | 1)3.1 cm2)0.7 cm | 1)3.4 cm2)3.4 cm | 1)0.9122)0.206 |
Rf =distance traveled by the substance /distance traveled by the solvent front
By examining the functional groups of the analgesic drug components, the relative strength of their polarities can be determined. For example, if a compound contains carboxylic acid, alcohol or amine functional groups, it should be very polar. If a compound contains ketone, aldehyde, ester, amide, or ether functional groups, it should be polar. Lastly, if a compound contains methyl or alkyl substituent functional groups, it should be non-polar. Thus, since caffeine has an amine and amide group, its relative polarity is the highest in comparison to the other three ingredients.
By understanding the relative polarities of the analgesic drugs, one could determine how the compounds will behave during the TLC separation. The stationary phase, silica gel in this experiment, is more polar, causing more polar components of a mixture to be more attracted to it. Thus, the more polar components will move more slowly and the less polar components will move faster on the TLC plates, having the highest Rf values. That is why in this particular experiment, caffeine, the most polar compound, has the smallest Rf value of 0.206 ; aspirin which is less polar than caffeine, has Rf value of 0.912.
In conclusion thin layer chromatography is a useful technique when trying to identify compounds and see how they separate. It is also a useful tool to see how polar or nonpolar a compound is. Overall the lab was very successful and the results that were found were solid.