INVESTIGATIONS ON NITROGEN COMPOUNDS AND NITROGEN METABOLISM IN PLANTS. I. THE REACTION OF NITROGEN COMPOUNDS WITH NINHYDRIN ON PAPER: A QUANTITATIVE PROCEDURE

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Abstract
To permit the development of the 2-directional paper chromatographic method into a quantitative procedure, the reaction between N compounds and ninhydrin on paper has been investigated. The principal variables involved in the process, which are temp., humidity, access to oxygen, concn. of ninhydrin and the composition of the solvent in which it is applied to the paper, have been separately identified and their effects detd. The conditions which permit the amino acids to react reproducibly with ninhydrin on paper involve heating to 60[degree]C, in an anaerobic (CO2) alcohol-saturated atmosphere. Certain of the amino acids which form blue compounds are determinable at 570 mu (cysteic acid from cystein, asparatic, glutamic and alpha-amino butyric acids, glycine, serine, threonine, alanine, glutamine, lysine, arginine, methionine sulfoxide and sulfone, valine, leucines, phenylalanine, tyrosine and tryptophan). Others which give brown compounds are measured at 330 m[mu] (asparagine, proline, and hydroxyproline). On this basis a method has been described in detail which now permits the ninhydrin to react reproducibly with the principal N compounds which occur in plants.