The separation of amino-acids by means of their copper salts

Abstract

TowN [1928] outlined a method for the separation of the amino-acids by means of their Cu salts and for the isolation of proline in a state of purity: in the present paper modifications of the method are described and the yield of proline from gliadin as determined by isolation as the picrate is indicated. Proline was first isolated by Fischer [1901] from the hydrolysis products of caseinogen by the ester distillation method. Later [1910] he improved the method of isolation, extracting the dl-proline with alcohol from the alkaline hydrolysate of gelatin and isolating it as the alcohol-insoluble Cu salt. This was the usual method of estimation of proline until Van Slyke suggested that it could be estimated by a determination of the non-amino-N in the alcoholsoluble portion of the amino-acids. This method gives results considerably higher than those of direct isolation; for example, in the case of gliadin, Osborne & Clapp [1906] obtained by isolation a proline content of 7-06 %, whereas later Osborne & Guest [1911] by Van Slyke's method found 13-2 %.