posted by Sheryl .
Question: What would happen to the Rf values of the pigments if you were to increase the relative concntration of acetone in the developing solvent?
Note: The development solvent used was 70% hexane - 30% acetone.
My answer: Acetone is more polar than hexane so the increase in its concentration would move the spots more rapidly up the plate and therefore would increase all Rf values.
Please check this.
That sounds ok to me but I'm a novice at TLC.
Rf value is calculated by distance spot traveled divided by total distance of eluent. So if you increase polarity of eluent and the spot travels further than before, you will actually DECREASE Rf value.
The Rf values would increase since you are increasing the polarity of the mobile phase. Normally the more polar the substance the slower it moves, however you are changing the relative polarity in the developing chamber.