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Students Identify Amino Acids

In a recent biochemistry laboratory session, students engaged in an experiment to identify amino acids within a mixture using a technique known as paper chromatography.

The procedure began with students preparing a chromatographic paper. They carefully placed concentrated spots of known amino acids along with a spot of the unknown mixture. Each spot was  labelled to ensure accurate identification later in the process.

Once the spots were applied, the paper was placed into a container with a small amount of running solvent. The solvent gradually moved up the paper by capillary action, carrying along the amino acids at different rates depending on their individual affinities for the solvent and the paper.

After 30 minutes, the paper was removed from the solvent and allowed to dry. The next crucial step involved spraying the paper with ninhydrin, a chemical that reacts with amino acids to produce a visible purple or blue colour. This reaction made the once-invisible amino acid spots apparent to the naked eye.

The students then compared the positions of the spots from the unknown mixture with those of the known amino acids. By matching the distances travelled by the unknown spots to those of the known samples, the students successfully identified the individual amino acids present in the mixture.

This hands-on experiment provided a clear demonstration of the principles of chromatography and the reactivity of amino acids with ninhydrin, solidifying the students' understanding of both the technique and the underlying chemical properties of amino acids.