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May 24, 2015

Homework Help: Mobility and Rf

Posted by Sheryl on Sunday, October 22, 2006 at 2:27pm.

We did a column chromatography then a TLC on extracted spinach pigments.

Question: Why are the chlorophylls less mobile on column chromatography and why do they have lower Rf values than the carotenes?

My answer: The chlorophylls are more polar than the carotenes so they adhere more more strongly to the alumina in the column, thus their slower mobility. The same principle applies to their movement up the TLC plate. Their slower mobility up the plate causes them to not travel as far as the carotenes when development is stopped. Since the further the substance travels the higher the Rf value, their Rf value is lower than that of the carotenes.

Is this okay?

Thanks for checking it.

Sheryl


I think it is fine Sheryl.

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