[alysha]

I want to do a lab on measuring the polarity of amino acids through paper chromatography. I know you can compare different polarities of different amino acids to each other in this way, but I want an independent variable that can be varied and measured. Are there certain factors that can be changed to directly affect the polarity of a single type of amino acid, such as increasing or decreasing pH?

[Babcock_Hall]

Changing the pH will change the net charge on any amino acid.  Some amino acids have ionizing side chains, but many do not.  You might want to check out the second edition of Thin Layer Chromatography, edited by Egon Stahl, starting on page 730.  Figure 205 shows the behavior of many amino acids in six different solvent systems, spanning acidic, neutral, and basic conditions.