Thin Layer Chromatography: Separation / Identification of compounds based on differences in their polarity
(Adapted from McMaster University's Experiments:
http://www.chemistry.mcmaster.ca
and the University of Colorado, Boulder:
http://orgchem.colorado.edu/hndbksupport/ochemlabtech.html )
TLC of Analgesic Drugs:
TLC Interpretation and Results (Read Lab Text/Guide pp. 153-160)
The developed TLC plate is the critical output of all TLC experiments and analyses. The intellectual challenge is to use all of the information from the method and plate to conclusively identify a component or components in a mixture. In research this is sometimes relatively simple, but often it can be quite challenging. The visualized developed plate below is highly idealized with a clearly distinguishable spot and Rf value. This is not always the case as in your experiment where one or more of the compounds may not move from the origin. However, this can be valuable information to distinguish the componenets. Also the plate may not have clear differences between Rf values where the compounds elute very similarly, which is often the case.
Below are two developed plates in plain light and under a UV lamp. The quality varies quite a bit. Which of the five compound's TLC traces are "textbook" and which are not? Consider what might cause the difference, such as applying too much sample. You are not expected to have a perfect TLC plate, but you must have information from the TLCs that conclusively supports the identification of your unknown.
There is no image of the plates after exposure to iodine vapor, which will stain the compounds differently, and will give you additional information to apply in the identification.
The TLC plates include the 5 reference compounds: #1 on the left = ace, asp, sal; #2 on the right = caf, ibu
asp - Aspirin (acetylsalicylic acid)
ace - Acetaminophen (4-acetamidophenol)
caf - Caffeine
ibu - Ibuprofen
sal - SalicylamideYour unknown is one of the brand names listed below. The structures for the active ingredents are provided. The check marks (horizontally) indicate what active ingredient(s) are present in each product. Your lab notebook Results section should include your unknown #, the commercial product's name, and the information that you used to support your identification.
