Experiment 61 Identification of Amino Acids in Food by Paper Chromatography

Experiment 61 Identification of Amino Acids in Food by Paper Chromatography 

The purpose of this experiment is to determine whether selected food samples contain certain amino 

Prepare 0.01 M solutions of leucine, methionine, valine, and lysine using a solvent that is 70% isopropyl alcohol and 30% water. Liquid food samples, such as fruit juice samples, can be used directly. Solid food samples must be soluble in the isopropyl alcohol-water solvent. Prepare solutions of solid samples as concentrated as possible. 

Using separate capillary tubes for each standard and sample, spot the paper by placing a small drop of each from the capillary tube at the appropriate points (where the lines cross). The smaller the spot the better. Perform this step carefully. Allow the spots to dry. Sample solutions should be spotted a second time over the original spot to make certain that there is sufficient amino acid in each spot. A single spotting is adequate for the four amino acid solutions. 

After 2 to 3 h (the longer the better), remove the paper, quickly mark the solvent front with a pencil, and hang the paper in a fume hood to dry. After drying for 5 to 10 min, spray the developed portion with ninhydrin solution (0.1% ninhydrin in butanol or isopropyl alcohol). Allow to dry for 10 min. Then place it in a drying oven at 100°C for 5 min. Amino acid spots will be violet to blue in color. 

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