Harduf, Z., Agricultural Research Organisation, The Volcani Center, Department of Animal Nutrition, P.O. Box 6, Bet Dagan, 50250, Israel

Amino as well as imino acids were detected with ninhydrin at a single wavelength of 405 nm, one of the absorption maxima of Ruhemann's purple, instead of the conventional 570 and 440 nm. The advantages are: (1) no need for a wavelength switch before and after the imino acid peaks; (2) avoids summing of the signals of 40 and 570 nm; (3) improves the sensitivity for most of the amino acids, particularly glutamic, cystine, methionine and lysine. The increase in the wavelength bandwidth, in order to increase the signal-to-noise ratio, is somewhat limited compared with that at 570 nm. © 1986.