An automated method of ammonia determination for use in mariculture

The precise and accurate determination of ammonia is important for both routine water management and research at a mariculture laboratory. An automated method was developed using a Technicon AA-II autoanalyser to measure total ammonia-nitrogen in seawater at both high (0-200 μmol l^-1) and low (0-10 μmol l^-1) ranges, using a single cartridge, with a precision of better than 2.2% (95% confidence). Phenol was used as the phenolic reagent, because sodium salicylate was found to be unsuitable for low level determinations of ammonia in seawater. The concentrations of nitrite usually found in mariculture tanks did not interfere significantly. Storage of filtered samples at 4°C in iodized bottles for 9 days or less gave an acceptable yield (± 5% of the initial value).