Enzymatic NH3-N determination: a specific method for the determination of ammonia in water and sediments

An enzymatic method for the determination of ammonia—nitrogen, not previously applied in water research, is described. The method is specific for NH₃-N, and the risk of hydrolysis of organic nitrogen compounds is very small, because of near neutral pH and low (room) temperature conditions. Differences between results of enzymatic NH₃-N determination and of a distillation method depended on the type of water. The method has been adapted for application in sediment research, where the exchangeable NH₃-N fraction is determined directly, without an extraction procedure. In comparison with this method, direct distillation of sediment samples gave an overestimation of the NH₃-N content of ± 40 per cent.