1953 年 73 巻 7 号 p. 675-676
It was found that colorimetric determination of α-amino acids was possible by reacting them with ninhydrin in pyridine, in the pressence of ascorbic acid. The experimental error was less than 5%, and the minimum amount of α-amino acids possible to be determined was ca. 0.5 γ converting into amino-nitrogen. The hydrindantin produced from ninhydrin and ascorbic acid, pyridine, and an excess of ninhydrin all had an effect of preventing the decomposition of the pigment, diketohydrindylidenediketohydrindamine.