A Micro Method for the Estimation of Am- Monia in Blood and in Organic Fluids

In an earlier publication’ dealing with a micro method for the estimation of urea in blood, I also described a micro method for the estimation of ammonia in blood and in organic secretions. For the determination of the ammonia two analyses are made; in the first the total urea plus ammonia is determined; and in the second the urea alone after the ammonia has been removed by evaporating the blood in vacuum. The difference between the two analyses gives the ammonia content. In the urea method itself the blood proteins are precipitated with 0.01 N acetic acid to which sodium acetate is added as a buffer. The precipitate is filtered off and the urea in the filtrate is estimated by means of its decomposition with hypobromite. The nitrogen produced is measured in Krogh’s micro respirometer and calculated with the aid of Krogh’s formula in terms of c.mm. When this figure is multiplied by 1.256 a correction for the weight of nitrogen is obtained in mg. and can, if desired, be found in terms of urea. For the purpose of this determination the micro respirometer is provided with ellipsoid bottles of 10 to 15 cc. capacity, fitted with ground glass stoppers on which are sealed small containers for the hypobromite. The determinations require from 0.10 to 0.15 cc. of blood and the error is ~kO.5 mg. per 100 cc. Since the value for the ammonia by this method is obtained as the difference between two such estimations, both subject to error, the possible error on the ammonia estimation itself is relatively high.