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Why is chromatography useful in the separation of photosynthetic pigments?
Question Date: 2007-11-04
Answer 1:

Chromatography is handy when you have something that looks like it's one color, but is actually made of many colors. Most leaves are green,right? But here in Wisconsin, the leaves are turning gold, orange, red,and yellow. What's actually happening is that those reds and yellows were already in the leaves, but the trees are taking the most valuable pigments out of the leaves to store for next year's leaves. The colors(pigments) that we think we see are actually made of several pigments.

Liquid chromatography separates all of the different pigments out, so we can see each on by itself. Water molecules stick to each other. That's why you can fill a glass to the top, then carefully add drops of water and make a "hill" of water above the glass. Water will also stick to pigments. In chromatography, you let water (or another solvent)dissolve the pigments, then let the water slowly move up a piece of paper. Not all of the pigments move at the same speed, so they separate out.

Think of a whole crowd of people getting ready to start a race. They're all bunched together. After they run for a while, the fastest will be up front, and the slower runners will lag behind. If you make everyone stop at the same time, you can see all of the runners clearly. (Of course, if you let them finish the race, they'd all bunch up again,that's why we stop chromatography before the water goes all of the way to the top.)

There are several great sites that show you how to do simple chromatography. Here's one, and once you are in, click on "experiments" and type chromatography for SEARCH:


Why do you think plants are green, anyway? And why do you think they have several pigments instead of just green?Hint: read up on light wavelengths.

Thanks for asking,

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