-1
$\begingroup$

I am confused about the basic understanding when it comes to TLC. I was under the assumption that less polar compounds move farther on the plate due to it having fewer IMFs. But I also heard that a more polar eluent will make the compound not move far. I'm not sure how to overlap these two findings which would have a better separation.

For example, I was given a question where we would match the eluent to the solvent plate. Some choices were 100% hexane, 85% ethyl acetate in hexane, 50% ethyl acetate in hexane, and 10% ethyl acetate in hexane. I thought the plate for 100% hexane would have spots near the solvent front because it is nonpolar, but those spots were closer to the start line. Visa versa for 85% ethyl acetate in hexane as the spots were closer to the solvent front even though it is very polar. What is the overlap in IMFs of compound found in the spots vs the eluent?

Improve this question
$\endgroup$
1
  • 1
    $\begingroup$ The whole question and discussion is meaningless without knowing the stationary phase coated on the TLC. What is IMF? $\endgroup$
    – ACR
    Commented Dec 10, 2023 at 3:05

1 Answer 1

Reset to default
-1
$\begingroup$

Aside of distribution of analyte between the phases, there is the factor of affinity of the mobile phase, or it's components, to the stationary phase.

If the stationary phase is polar and if the mobile phase contains a polar enough component, it has tendency to wash everything out.

It can be frequently seen the system has the second solvent front and the stationary phase looks differently when it passes.

It is clear that ethyl acetate is washing out your analytes.

Improve this answer
$\endgroup$

Not the answer you're looking for? Browse other questions tagged or ask your own question.