This experiment uses paper chromatography to determine whether a sample is a mixture of amino acids and to identify the components of the sample. Paper chromatography employs the competing tendency of amino acids to dissolve in a chosen mixture and move them over a stationary material due to differences in their polarity. The mixture used to pass over the stationary material is of methyl ethyl ketone, propionic acid, and water. By passing that mixture slowly through a stationary material, paper in this case, the differentiation of the amino acids' polarity becomes possible. The differentiation is recognized because each one's competing tendency to dissolve will cause certain compounds of solvents to move through relatively quickly, since they are very soluble in the fluid and only weakly absorbed, and some to move through very slowly, because they are much less soluble in the fluid and are strongly absorbed. In relation, a very polar compound will move further up the stationary material while one that is not as polar will remain closer to the baseline of a chromatograph. This results in different distances traveled along the stationary material for different compounds and allows for chemical observation if the manipulation of other properties is difficult when attempting to determine the identity of a solvent. In this experiment, several known amino acids are placed on the stationary material to be moved some distance by the mixture and then three unknown solvents that are a mix of the known amino acids are also placed side by side with them. The characteristics of the spots made by the amino acids and the distances they moved should be paralleled by the compounds in the unknown solutions, allowing for identification of the amino acids. .
The purpose of this lab is to separate amino acids from their solvents by manipulating their solubility in relation to polarity and to distinguish and identify them.