title: Preservation of urine for ammonia determination with a direct method.
mesh_terms: D000641:Ammonia / Q000652:urine*; D005615:Freezing; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007215:Indophenol; D008722:Methods; D013048:Specimen Handling; D013997:Time Factors
chemical_list: D007215:Indophenol; D000641:Ammonia