Chromatography is the process of physically separating substances in order to be identified and analyzed. The major factor that affects chromatography is the type and saturation of the solvent being used. The dimensions of the chromatography paper, temperature of the solution, and particle size of the solution all act as factors on the rate of chromatography as well. In our particular lab, we focused on the chromatography of pigments in leaves. The purpose of the chromatography paper was to distinctly show the separation of pigments, and the purpose of the solvent is to move the pigments up the chromatography paper through capillary action in order to separate the pigments. Before testing on leaf pigments, we used chromatography to separate the pigment colors in a black marker. The results were actually quite beautiful.
In our lab, part of the purpose was to find the Rf value of each pigment. The Rf value stands for Relative Mobility Factor, which is referring to the movement of a substance in relation to the other protein bands. It is calculated by (Dunknown)/(Dsolvent). Dunknown stands for the distance that the solute traveled up the chromatography paper and Dsolvent stands for the distance the solvent traveled up the chromatography paper. Because each substance/pigment has a different Rf value, scientists can study the value in order to identify different types of pigments.
After testing chromatography using marker, we went on the the actual lab: using chromatography to separate the pigments in plant leaves. Our results were as following:
Our group was only able to identify two types of pigments in the green leaf: Carotene (the orange band) and Chlorophyll a (the light green band). In the purple leaf, we were able to identify carotene as well, and some other unknown pigment, which made a purple color. What we noticed is that in the purple leaf, that purple pigment masked the bands of the other pigments – however, it was evident that there were still other pigments there. Our group really enjoyed this lab because it is so aesthetically appealing. However, we found it hard to identify the different colors and to be able to tell where the rings were, because they faded a great deal. In our two green leafs, the results of the Rf value were extremely close (.88 and .89) which correlates with the fact that if the conditions for a set of chromatography are consistent, the Rf value will be constant as well. In plants, pigment is the means of which the energy of the sun is captured for photosynthesis, because pigments absorb the light energy and transfer it, which excites the electrons and thus makes way for the beginning steps of photosynthesis. My major question after doing this lab is how/why plants change color in the fall. I don’t understand how pigments are added or taken away for the start of the new season, or how one suddenly becomes dominant and masks the other.
Thanks for reading! Make sure to MicroSCOPE out the rest of my blog!
*All photos taken by our lab group*
“Affect of Different Colored Lights on Photosynthesis.” Affect of Different Colored Lights on Photosynthesis. CU Boulder, n.d. Web. 04 Oct. 2014.
Light Absorption for Photosynthesis.” Light Absorption for Photosynthesis. N.p., n.d. Web. 04 Oct. 2014.
MicroSCOPE It Out 