Rapid Determination of Plasma Ammonia by an Ion-exchange Technic.

A method is described for the colorimetric determination of ammonia in plasma by a batch ion-exchange procedure. The method combines separation of ammonium ion, using a strongly acidic cation-exchange resin, with a sensitive colorimetric procedure which simultaneously elutes and colorimetrically reacts with the ammonium ion to produce a stable color. Interference by basic amino acids is negligible, and the great sensitivity of the color reaction permits the measurement of ammonia of the order of 0.5 g./ml. The effects of variations in the experimental conditions are examined, and the results of recovery experiments and other tests of precision and accuracy are reported. In comparison with other methods in current use, this method has distinct advantages in sensitivity, simplicity, and rapidity of determination, provided the conditions and methods of measurement are controlled carefully.