Question

Bob the chemist ran a TLC plate of his product, but the spot would not move off the baseline. The eluent he used consisted of a 30% polar / 70% non-polar solvent system. Which solvent system should he try next in order to get the compounds in his product mixture to move up the plate

Answer 1

40 % polar / 60 % nonpolar system

Step-by-step explanation:

According to the like-dissolves-like rule, remember that polar compounds dissolve in polar solvents and nonpolar compounds dissolve in nonpolar solvents.

Notice that the eluent used is only slightly polar and mainly nonpolar. Since the product didn't move at all, this means it didn't interact with the major nonpolar solvent and is expected to be polar.

That said, a more polar system should be used in order to make the product move off the baseline, such as 40 % polar and 60 % nonpolar solvent system.

In case the product still doesn't move, polarity of the eluent should be increased further.