Determination of citrulline in plasma.

THE ONLY METHOD available at present for the routine determination of citrulline in blood is the one first described by Archibald (1). This method is based on the original observation of Fearon (2) that in strongly acid solution citrulline condenses with diacetylmonoxime (DAM) to produce a peach-colored complex. Since urea also reacts with DAM under these conditions, Archibald removed it by incubating the blood sample with urease. Elodi (3) modified the method by adding phenylhydrazine to the reaction mixture. He reported that with this modification citrulline and urea could be determined in the presence of each other by measuring the absorption of the reaction mixture at two different wave lengths. However, all of his determinations seem to have been carried out at concentrations very much higher than those present in blood. Pearl and McDermott (4) slightly modified the method of Archibald by changing volume relationship during the dialysis step. The purpose of the present study was to devise a precise method for the determination of citrulline in plasma which would eliminate the tedious dialysis step, and if possible modify the color reaction so that the product would obey Beer’s law.