Nitrogen analyses in eutrophic, alkaline and peaty waters: a comparison of different methods to analyse ammonia-nitrogen

Because of problems of ammonia determination in eutrophic and peaty Lake Tjeukemeer, different methods of analysis [(a) the salicylate method, (b) the classic distillation procedure at alkaline pH; (c) the method of oxidizing ammonia to nitrite; and (d) the glutamate dehydrogenase method] were compared. Prior to salicylate addition or ammonia oxidation to nitrite, the peaty samples—filtered and buffered at pH 6.5 to avoid ammonia losses—were led through an Al 2O 3-column of the same pH to remove interfering substances. In this way the results of the salicylate method fitted best with those of the specific enzymatic method.