posted by Leon on .
For a TLC lab,the stationary phase is the mixture of isopropanol and ammonia or the mixture of hexane,ethyl acetate and ethanol, the stationary phase is silica gel. text some dyes and drugs.
what is the relationship between the polarity of molecules and the Rf values?
Read your first paragraph. It makes no sense.
The second paragraph containing the question does. The Rf value increases with decreasing polarity. That is, increased polarity of the molecule means it is attracted more to the polar stationary phase; therefore, it moves less and the Rf value is less.
Also, for the same situation, which one of the two mobile phases is the more polar? Actualy I need two pieces of evidence... I think the polar one should be the isopropanol and ammonia because it moves slower. Can you help me come up another reason? Thank you~