January 28th, 2015
CHEM 237 – Organic Chem Lab
TLC Analysis of Analgesic Drugs
1. Once 2 TLC plate were obtained, a line about 1 cm from the bottom (solvent line) and from the top (solvent front) of the plate was drawn using a dull pencil on the side that has the silica (DON’T use ink!). A developing chamber was obtained with 5 mL of the TLC developing solvent, which was already pre made, poured inside. The depth of the solvent was no more than 0.5 cm or at least below the drawn solvent line. A watch glass was put on top of the beaker to seal in the solvent.
2. On the TLC plate, markings were prepared and spotted in the appropriate spots using capillary spotters. Repeat the process using clean capillaries each time for the remaining solutions. Once the solvent front is reached, the TLC plate was removed immediately and set out to dry.
3. When the plate is dry, the chemicals present were not colored, however, they absorbed UV light. Looking at the TLC plate under the UV light, carefully the spots seen were lightly circle with a pencil in order to indicate and show the progress. The TLC plate was set aside for measurements at the end of the experiment in order to have the Rf values calculated.
4. Part two’s procedures were the same with the exception of the unknowns (aspirin and ibuprofen) were heated in 5 mL of Etoh and 5 mL of DCM and then spotted on the TLC plate.
TLC, or thin layer chromatography, technique was performed on a sheet of aluminum foil, which is coated with a thin layer of absorbent material like silica gel. This layer of silica surface has atoms attached to hydroxyl group and the surface is very polar.
Different compounds in the mixture travel at different rates due to the difference in the attraction to the stationary phase and the differences in solubility