From: Lizzie Heath
Date: March 4, 2013
Subject: Thin-Layer Chromatographic Analysis of Drug Components (Experiment #15)
The purpose of this experiment is to determine the components of an unknown drug and identify it as one of six (6) commercial drugs by using thin-layer chromatography.
I added approximately a quarter of a tablet of acetaminophen, aspirin, caffeine, ibuprofen, salicylamide, and the unknown (#19) to separate test tubes containing 2.5mL of dichloromethane. I noticed that my unknown was a coated tablet. Each test tube was swirled until the greatest amount of each solid was dissolved. Each solution was spotted along a labeled starting line on the silica gel TLC plate. The TLC plate was put into a developing chamber containing 200:1 acetic acid and allowed to developed until the solvent reached almost to the top of the TLC plate, which took about 10 minutes.
When the TLC plate finished developing, I observed the plate under UV light and noticed that the salicylamide was the only spot that fluoresced purple while all the other spots fluoresced blue and I also noticed that the unknown had 2 spots. I traced around the spots for each solution on the TLC plate, the only spot that I did not see was the one for the ibuprofen. I then placed it into an iodine chamber and noticed that the acetaminophen turned a yellowish color.
I measured that the solvent traveled 64mm up the TLC plate by using the starting line as a reference, and, by using that information, I was able to calculate the Rf value of each solution by using:
Rf= distance traveled by the spot Distance traveled by the solvent
I used that formula to get the following information for the table below:
Commercial Drug Rf Value
Acetaminophen 0.500
Aspirin 0.781
Caffeine 0.125
Ibuprofen 0
Salicylamide 0.719
Unknown 0.109 & 0.734
I am able to determine that my unknown substance contains aspirin, but I am not sure what the other substance is. I can speculate that the other substance is the coating from the tablet of the unknown.
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