Question

How does polarity affect chromatography?

Answer 1

Chromatography is a method for separating mixtures based on differences in the speed at which they migrate over or through a stationary phase. This will separate complex mixtures of chemicals or proteins into their various different components.
Polarity has a huge affect on how attracted a chemical is to other substances. Some molecules have a positively charged side and a negatively charged side. For example, the positive side is attracted to the negative side of another molecule (opposites attract). The larger the charge difference, the more polar a molecule is.
You will find that as you increase the polarity of the solvent, all the components of the mixture move faster during your chromatography experiment.

Here is a video which shows a paper chromatography experiment which was conducted to separate the pigments found in a black overhead marker. The different colors of pigments have different solubilities based on their polarity. The blue pigment has a greater solubility in water so it moves faster (goes higher) through the chromatography paper. The yellow pigment is less soluble so it moves more slowly.