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Reaction of Ninhydrin with Amino Acids

Ninhydrin reacts with amino acids to produce a violet compound.

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Narrative
Water is spotted on a piece of paper. A solution of glutamic acid is also spotted on the paper. The paper is dried with a heat gun. Ninhydrin solution is sprayed on the paper to allow it to react with the amino acid. As the paper dries and is heated, the ninhydrin reacts with the amino group on the glutamic acid to produce a violet compound. There is no reaction with the water and ninhydrin.