Science Buddies: "Ask an Expert"

Does/can the retention factor, obtained from performing paper chromatograpy on plants, tell you how much chlorophyll there is in a certain leaf?

My project is about trying to find where a plant keeps its most chlorophyll by performing paper chromatography.

good project idea

Anyone who can answer my question it would be greatly appreciated!

chillmanjr wrote:Does/can the retention factor, obtained from performing paper chromatograpy on plants, tell you how much chlorophyll there is in a certain leaf?

My project is about trying to find where a plant keeps its most chlorophyll by performing paper chromatography.

No, the rf factor only tells you about the identity, not the quantity of the chemical. The darkness of the spot might tell you something qualitative about the amount of the compound, but this isn't accurate, and it depends very much on loading (how much you put on the paper- and more can lead to less compound at the a band or streaking) and extraction (for example, maybe you only extract 50% of chlorophyll from sample 1 and 10 % from sample 2). You could do some simple experiments to test these two statements. Make a chlorophyll solution and then make several dilutions. Being careful to put exactly the same amount per same size spot, run all the concentrations. From the color intensity change can how quantitative can you get? If you use a digital camera and a computer program to measure the lightness of the green spot can you get more accurate? I don't know that this method will work- maybe depends on how good your camera/software is.

As for the second part. extraction, you need to test several methods to make sure you extract all pigments. The protocol for leaves might be different than the method for stems. Ideally, you could find a method that would remove 100% of the color and leave you with white plant matter.

Hope this helps. Good luck!

Louise