To our knowledge, there exists no single rapid technique for the quantitative separation of the amino acid intermediates of the Krebs-Henseleit urea cycle. In this cycle, ammonia is converted to urea by a series of reaction beginning with the condensation of l-ornithine with carbamyl phosphate and proceeds sequentially through citrulline, argininosuccinic acid, and, finally, arginine, which is the cleaved to form urea with regeneration of ornithine. This communication describes chromatographic methods which have been found to give satisfactory separation of these compounds in a variety of mixtures. The time required for the separations is slightly over 2 hr which compares favorably with the 12-18 hr needed for papar chromatography or the time required for separations by automatic amino acid analyzers.
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