Chromatography can be used in biochemistry to identify amino acids. In essence, the process goes like this:
- Apply small spots of amino acid solution to chromatography paper (a type of filter paper used as the adsorbent), and mark their position.
- Roll the paper into a cylinder and stand in a solvent inside a glass beaker. Mark the position of the solvent. (There are a number of appropriate solvents, based around simple organic substances such as butyl alcohol and acetic acid.)
- Wait until the solvent level has nearly reached the top of the paper.
- Dry the paper, but do not apply a direct flame.
- Apply ninhydrin spray (which is nasty stuff, so take care).
- Heat in an oven for around 10 minutes.
- Measure the distances moved by the solvent and the acid(s).
Calculate the Rf value for each acid, which is the distance it has moved divided by the distance the solvent has moved.
R
f values for
amino acids in different solvents have been determined, so these can be used to determine which ones you've got in your sample.