Distinctive test for alpha-amino-acids in paper chromatography

IN the amino-acid analysis of biological fluids using paper chromatograms1, the ninhydrin reaction indicates by means of a purple coloration not only α-amino-acids but also many other types of amino-acids and amines2. Spots that do not correspond in their positions on the paper to known substances are often found in these fluids. The circumstances sometimes preclude the possibility of isolating and analysing such substances, so that we may be limited to provisional identifications based entirely on paper chromatographic procedures.