Title: Influence of Cations on the Ninhydrin Reaction for the Determination of Amino-Acids
Abstract: THE micro-determination of α-amino-acids with ninhydrin in n-butanol is highly sensitive, but often inaccurate due to the retardation of colour formation and the production of various red or blue colours instead of the purple compound usually obtained. It was found that traces of cations had a marked influence on the speed of colour formation and its intensity and on the absorption spectra of the coloured compounds produced. (The effect of cations on the ninhydrin colour was employed for the preservation of chromatogram spots by Kawerau and Wieland1.)