Ninhydrin Reaction

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Ninhydrin Reaction


a color reaction used for the qualitative and quantitative identification of amino acids, imino acids, and amines. Upon heating in an alkaline medium with substances containing primary amino groups (— NH2), ninhydrin (triketohydrindene hydrate, C9H6O4) yields a product with a stable deep blue-violet color, with maximum absorption at about 570 nanometers. Since absorption at this wavelength is a linear function of the number of free amino groups, the ninhydrin reaction is the primary means of quantitative identification of amino groups in colorimetry and spectrophotometry. The ninhydrin reaction is also used to detect secondary amino groups (> NH) in imino acids (proline and hydroxyproline); a bright yellow product is obtained as a result of the test.

The sensitivity of the ninhydrin reaction is up to 0.01 percent. Modern automatic amino-acid analysis is carried out by combining the ion-exchange separation of amino acids and their quantitative identification using the ninhydrin reaction. The reaction is also used to detect each type of amino acid present in quantities no smaller than 2–5 micrograms when techniques of paper chromatography are used to separate mixtures of amino acids.


References in periodicals archive ?
Besides amino acids, other complex structures such as peptides, peptones and proteins also react positively when subjected to the ninhydrin reaction.
Therefore it is thought that the difference of removal of protein when washed with the carbon dioxide warm water instead of the tap water is seen as shown from the ninhydrin reaction.
Quantitative monitoring of solid-phase peptide synthesis by the ninhydrin reaction.
Initially, tHcy was measured with amino acid analyzers, using the ninhydrin reaction as the method of detection.
Experiments with and without leaf tissue confirmed that the interference was nonenzymatic and that [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] interfered with the ninhydrin reaction.
The Isolab phenylalanine test kit is a modification of a fluorometric procedure involving a ninhydrin reaction, as published by McCaman and Robins [4].
Although the analytical approach is very conventional, AAs being separated with a cation-exchange resin and their concentration determined with the ninhydrin reaction, the instrument provides for extemporaneous automatic mixing of the detection reagent.