A spot analysis for cysteine on silica gel thin layer

GOSHIMA Fumiaki, ISHINO Fumie

doi:10.2116/bunsekikagaku.28.2_116

Color reactions of 20 amino acids on silica gel thin layer with ninhydrin dissolved in sulfuric acid were studied. The procedure is as follows: A sample solution was prepared by dissolving 5 mg of each amino acids in 1 ml of 0.5 M hydrochloric acid and the spray reagent was made by dissolving 0.1 g of ninhydrin in 10 ml of 1 M sulfuric acid. Five μl, of the test solution was spotted on a thin layer of silica gel (Merck, Type-60). After drying, the plate was sprayed with the ninhydrin reagent and heated at 80°C for 15 min. A characteristic reddish-purple spot was observed when cysteine was present in the test solution. The detection limit was 0.1 μg when 5μl of the sample solution was used. However, other amino acids, except tryptophan (yellow) and hydroxyproline (light brown), gave no color with the reagent. The colored products of tryptophan and hydroxyproline were separated by adding a drop of 6 M acetic acid on the colored spot, while the colored product of cysteine remained at the origin and turned. purple. Therefore, the detection became more sensitive and selective. This method serves as a rapid and convenient spot analysis of cysteine in amino acids mixture.

A spot analysis for cysteine on silica gel thin layer

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