Tlc Sheet

GUIDE QUESTIONS:

1. What compounds are present in the unknown tablet?

The compound present in the unknown tablet is caffeine

2. Tape the TLC sheet here or copy/illustrate the chromatogram. Cover the whole sheet with clear tape to protect it.

3. Suggest possible advantages and disadvantages of using a longer (taller) TLC sheet?

Advantages:

The results may be more accurate because the compounds may stop to run where they should really stop since while we were using the 5-cm TLC, we had to pull it out because it the solvent was still running until it almost reached the other end.

Disadvantages:

The spot of the compound may be harder to see or will be less visible even when placed under the UV lamp.

4. Why do you think it was important to use a very small amount of sample when spotting the plate?

It was important to use a very small amount of sample when spotting the plate because there would be a chance that overlapping may occur within the compounds which will make the results inaccurate since it would be hard to see each spot.

5. The relative movement of components is controlled partially by the polarity of the molecules. The TLC sheet is coated with a highly polar substance, whereas the solvent mixture has a much lower polarity. From your chromatographic results, predict the relative polarities of aspirin, paracetamol, ibuprofen and caffeine by arranging them in order of increasing polarity. Explain your reasoning.

(Lowest to highest polarity) - Ibuprofen, aspirin, paracetamol, unknown/caffeine. Caffeine was considered having the greatest polarity because the lower the distance, the greater the polarity. Since caffeine was the closest to the line where it was spotted first, when its Rf is calculated, it will have the lowest value which means it has the greatest interaction with the polar adsorbent on the TLC plate.