Introduction: One of the most sensitive techniques in Biochemistry for separating mixtures of different molecules is the technique of Chromatography. This technique depends on the ability of a mixture of solvents ("solvent system") to separate tiny amounts of a substance, called the solute, from the other solutes present in the mixture. Because each substance (solute) in the mixture is more or less soluble in the solvent than another.
Even though there are many forms of Chromatography (ex: gas chromatography and thin layer chromatography) the form used in this lab is called "Paper Chromatography". This method is sensitive and can separate as many as a dozen or so molecules one from the other.
To see how the process of chromatography can be used to separate the light absorbing, photosynthetic, pigments of spinach leaves.
In this exercise you used a technique to separate the colored pigments found in the leaves of spinach. As you conducted this lab you saw several colors; Two bands of green- one blue-green band, and one yellow-green band, which correspond to the two kinds of chlorophyll which is used to absorb light energy from the sun. You also saw a band of yellow which corresponded to a group of pigments called xanthophylls and a band of orange that corresponded to a group of pigments called "carotenes".
During this lab you may also may have seen a band of faint gray, between the carotenes and the xanthophylls, called pheophytin. All of the pigments are involved, in some way, to the photosynthetic process. The non-chlorophyll pigments are called "accessory pigments" and play an indirect yet important role in photosynthesis. The pigments found closet to the origin at the bottom of the piece of paper are the least soluble, and the one which moved the farthest up the paper are the most soluble in the solvent system.
©Copyright 1998 Elizabeth
Beckett, Holly Bernitt, and Vishwa Chandra.