Colorimetric determination of blood and brain ammonia in vitro by a modified method

A modified method that incorporates Conway microdiffusion to trap ammonia and indophenol reaction for colorimetric determination of microquantities of free ammonia in blood and brain samples is described in this paper. By this method, 60-70% of ammonia could be recovered from a known ammonium chloride solution. Blood and brain of adult female rats (control) measured 1.41 +/- 0.24 mu g/ml and 5.47 +/- 0.61 mu g/g, of ammonia respectively. The method was tested by dertermining blood and brain ammonia concentrations 15 min after intraperitoneal injection of ammonium chloride (100 mg/kg and 200 mg/kg) in female rats. The method is simple and sensitive and is useful for determination of microquantities of ammonia in blood and brain samples in experimental animals.