A Simple and Rapid Procedure for the Determination of Amino-nitrogen and Ammonia in Urine

The ninhydrin-colorimetric procedure for the determination of urinary 2 amino-nitrogen has been simplified by the use of the Conway microdiffusion unit to remove ammonia from the sample. In this way, urinary ammonia is measured, and at the same time an ammonia-free urine sample is ready for 2 amino-nitrogen analysis. Values for total and free 2 amino-nitrogen in normal urine samples were found to be similar to those previously reported by more complicated procedures. THE METHOD described by Rubinstein and Pryce for the determination of amino-nitrogen in tissue fluids requires that all traces of ammonia be removed from the sample (1). In their method, this was achieved#{149}by adding potassium carbonate to the sample and evaporating to dryness in a vacuum desiccator, usually overnight. The sample is then dissolved in distilled water and amino-nitrogen determined. Their procedure may be simplified by the use of the Conway micro-diffusion unit to remove the ammonia from the urine sample. In this way, urinary ammonia is measured according to Conway (2), and at the same time, an ammonia-free urine urine sample is ready for amino-nitrogen analysis. Method Reagents and material for microdiffusion procedure are as described by Conway except that 1.0 N NaOH was used in place of saturated K2C03, and in some cases, 6 N HOSO4 was used in place of the borate buffer to absorb ammonia. Reagents and materials for colorimetric estimation of amino-nitrogen are as described by Rubinstein and Pryce (1)