Chromatography is the separation of the molecules of a particular substance that is represented by different colored bands on chromatography paper. The solubility of the molecules in the solvent, the adhesion of the molecules to the paper, and the mass of the molecules allow chromatography to happen. The solvent moves against the force of gravity by capillary action, which occurs due to the adhesion of the solvent to the paper and the cohesion of the solvent molecules. The chromatography paper participates in the separation of the molecules of a substance by drawing up the solvent and allowing the movement of the molecules of the substance. The separation of these molecules on the paper is determined by variations in the mass and solubility of the molecules. The paper also provides a platform by which the distance from the initial site of application and color of the pigments can be observed.
The Rf value (reference front) is represented by the equation: . The Rf value must be useful to scientists as the values allow scientists to identify the molecules that are present in a particular substance because each molecule has a specific Rf value, and the values can be used to compare the masses of molecules based on the distance travelled. D unknown signifies the unknown distance travelled by a pigment from the initial site of application. D solvent is the distance travelled by a solvent from the point of contact with the paper.
Two pigments were identified on both the green leaf chromatogram and the non-green leaf chromatogram. Yellow and green were the two pigments identified on the green leaf chromatogram. The yellow pigment was very close to the initial site of application, whereas the green pigment was not. Purple and red were the two pigments identified on the non-green leaf chromatogram. The purple pigment was very close to the initial site of application, whereasthe red pigment was not. From this experience, I learned that there are different types of pigment in leaves that capture the light energy from the sun that is used in photosynthesis. These pigments absorb and reflect certain wavelengths of light. Chlorophyll a is the most common and has a green color. To learn more about which wavelengths certain pigments absorb and reflect, click here to view my Prezi on the topic: How Do Different Colored Lights Affect Photosynthesis?
Chromatography setup. Digital image. Pearson Education Inc., Web. 9 Oct. 2013. http://www.phschool.com/science/biology_place/labbench/lab4/design1.html.
Clark, Jim. “Paper Chromatography.” Chem Guide. 2007. Web. 9 Oct. 2013. http://www.chemguide.co.uk/analysis/chromatography/paper.html.
Reece, Jane B., Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, and Robert B. Jackson. Campbell Biology. 9th ed. San Francisco: Pearson Benjamin Cummings, 2011. Print.