+ Chromatography of Amino Acids A mixture of amino acids can be separated by chromatography and identified from the amount they have moved. Rf value = distance moved by amino acid distance moved by the solvent Each amino acid has its own Rf value Method Take chromatography paper and draw a pencil line 1.5cm from bottom. With a capillary tube put a small drop of amino acid on pencil line Roll up paper and stand it in a large beaker. The solvent in the beaker should be below the pencil line. Allow to stand for 20 mins and mark final solvent level Spray paper with ninhydrin and put in oven. If ninhydrin is sprayed on an amino acid and then heated for 10 minutes then red to blue spots appear. This is done because amino acids are transparent and cannot be seen.
220.127.116.11 Proteins (A-level only)
Amino acids can be separated and identified by thin-layer chromatography.
Amino acids can be located on a chromatogram using developing agents such as ninhydrin or ultraviolet light and identified by their Rf values.
Students should be able to:
• calculate Rf values from a chromatogram.