Permanganate as a Spraying Reagent for Amino-acids on Paper Chromatograms

POTASSIUM permanganate (1 per cent solution, containing 2 per cent sodium carbonate) has been recommended 1 as a spraying reagent for detecting carbohydrates on paper chromatograms. When testing this reagent on a chromatogram irrigated with butanol/acetic acid and carrying amino-acids as well as carbohydrates, an anomalous spot was observed, which was traced to methionine. It has now been found that if a paper chromatogram be lightly sprayed with the permanganate reagent, methionine, tryptophane, tyrosine and (more weakly) proline and histidine immediately appear as yellow spots on a red background. As the paper dries the colour difference tends to disappear, leaving the spots and background different shades of brown. The spots should therefore be marked at once. Cysteine also gives a spot, but does not normally occur on a paper chromatogram 2 . Threonine, hydroxyproline, lysine and glycine show up on standing a few minutes. Other amino-acids normally occurring in protein hydrolysates do not show at the concentrations encountered in paper chromatography.