Question

TLC can be used to confirm the components of over-the-counter analgesics. Assuming that you have pure standard samples of caffeine, ibuprofen, acetaminophen, and aspirin, how would you determine if a new analgesic contains any of those four components? Provide information on how you would prepare the samples for analysis and how you would set up the TLC experiments.

Answer 1

Preparation of sample for the analysis:

It is very simple. We need to dissolve the pure analgesics and the analgesic to be identify in a polar solvent which is volatile in nature (usually ethyl acetae or acetone).

TLC experiment and setup:

The TLC plate contanis base line and solvent front (represented in the image). In the base line, we need to spot small amount of our dissloved pure analgesics and the new analgesic using a small capillary tube. The base line is the line drawn on the bottom of the TLC plate.

And this spotted TLC plate is placed into the small beaker containg a mixture of polar and non-polar solvent and the beaker should be closed. This beaker is known as TLC chamber or elution chamber.

Remove the TLC plate once the elution of the solvent is over till the solvent front, which is the line on the top of the TLC plate.

Identification of the compounds:

TLC is based on the priciple of the polarity of the compounds. Each compound has a different polarity. Thus each compound elute in the TLC plate at a different rates and it will be in the different position in the TLC plate after elution.

TLC plate is coated with the silica gel, whch is polar in nature. If our compound is highly polar, then it will adsorb with silica more effectively and if our compound is less polar it will not adsorb with sillica as much and it will run through the TLC plate during elution.

Thus the distance travelled from the base line by the non-polar compound will be greater than the polar compound.

If we spot our new analgesic along with the pure compounds in the same TLC plate and after elution, there will be a spot in the new analgesic on the same position as any one of our pure compound. This confirms the presence of the anyone one of the analgesics in the new tablet.

In this way we will identify the presence of the compounds.