Science Buddies: "Ask an Expert"

Hi! We are having trouble getting good results with paper chromatography of leaf pigments. We can't get the pigments to drop out and the solvent continue further. The pigment just goes all the way to the end of the paper with the solvent, where it can't really be seen. Our paper strips are 6" long. We have tried isopropyl alchohol, acetone, and combinations of the two. We are very frustrated, as this project looked so easy and straightforward, but we are now worried that we will have to start over at the last minute with something else if we can't get our experimental technique to work! Thanks for any advice you can give us!

Hi,

You have picked a really great project from the Science Buddies website.

https://www.sciencebuddies.org/science- ... background

The project guide specifies isopropanol, which is a polar solvent. Acetone is less polar. One of these solvents should be suitable for solubilizing the plant pigments, which you are trying to separate.

Here are some suggestions and questions to answer that may help solve the problem.

1. Have you tried a different brand of paper towels?
2. Did you concentrate your sample before applying it to the paper towels?
3. Try covering the Mason jar to saturate the atmosphere in the jar with the solvent
4. Have you tried 100% acetone?
5. What types of leaves are you working with?
6. The procedure in the experiment is very detailed. Can you confirm that you followed every step? Did you vary any of the steps at all?
7. Applying a very concentrated spot of the plant pigment at the origin is very important for success. Was the starting color spot a very intense color? If not, try applying lots more pigment.

Please post again if you don’t see separation of the pigment colors with answers to the questions. You definitely do not need to change projects.

Donna Hardy