Comparison of Nessler, phenate, salicylate and ion selective electrode procedures for determination of total ammonia nitrogen in aquaculture

Abstract An assessment was conducted to compare the precision and accuracy of Nessler, phenate, salicylate, and ammonia electrode procedures for total ammonia nitrogen (TAN) concentration determination in waters of aquaculture. Salicylate method was selected as a standard method for its high precision and accuracy. In replicate analyses of water samples for precision estimate, Nessler method usually gave higher mean concentration of TAN than other methods and it is not recommended for use for its high coefficient of variance. Results from Nessler's with Rochelle salt method were more accurate than Nessler without Rochelle salt method. Electrodes for sensing NH 3 and NH 4 + usually gave higher mean concentration of TAN than salicylate method. NH 4 + electrode, although with high accuracy, was strongly affected by sodium and potassium and not recommended to use especially in waters of high salinity. The finding also suggested that the salicylate kit by using YSI photometer also was a preferable alternative to salicylate method while Nessler kit was not. TAN concentrations measured in 27 water samples by all methods were highly correlated (R 2  = 0.919 to 0.996) with salicylate method. All of the slopes except phenate I and II method were different from 1.0 ( P P Statement of relevance In this study, we evaluated the accuracy and precision of different possible ways of measuring TAN concentration at aquaculture facilities. These findings will be useful because producers need reliable measurement of TAN concentration to effectively manage ponds and other culture systems. The conclusions made in this manuscript provide valuable information when researchers and farmers need to measure TAN concentration.