You carry out tlc on silica gel of a mixture of compound A and B. Using a mobile phase of hexane 50% and acetone 50% the Rf values of were A 0.15, B 0.2, and the spots were overlapping. What change would you make to the solvent composition to improve the separation? Explain.
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To improve the separation of compounds A and B in the TLC experiment using a mobile phase of hexane 50% and acetone 50%, you can modify the solvent composition by adjusting the ratio of hexane to acetone.
Here's what you can do:
1. Increase the polarity of the mobile phase: Since the spots of compounds A and B are overlapping, it suggests that the mobile phase is not polar enough to facilitate their separation. You can increase the polarity by increasing the proportion of the polar solvent (acetone) in the mobile phase.
2. Decrease the nonpolar component: In the given scenario, hexane is the nonpolar solvent in the mobile phase. By reducing the amount of hexane and increasing the proportion of acetone, you can enhance the separation of A and B.
3. Adjust the hexane to acetone ratio: Start by making small changes to the ratio of hexane to acetone, such as using a mobile phase of hexane 40% and acetone 60%. Perform a new TLC experiment and check if the spots of compounds A and B are better separated. If not, you can further increase the polarity by using hexane 30% and acetone 70% or even higher ratios until an acceptable separation is achieved.
4. Repeat the experiment: After making changes to the mobile phase composition, it is important to repeat the TLC experiment to check if the separation has improved. The Rf values for compounds A and B should increase, indicating better separation, while still maintaining a reasonable distance between the spots.
It is worth noting that TLC optimization is often an iterative process, and the choice of mobile phase depends on the specific properties of compounds A and B. You may need to experiment with different solvent systems and ratios until you achieve the desired separation.