Simultaneous determination of nutrients (ammonium and phosphate) in marineaquaculture effluents by flow analysis

In this work, a flow analysis method with spectrophotometric detection has been developed for the simultaneous determination of phosphate (P-PO43-) an d ammonium (N-NH4+) in marine aquaculture effluents. The method is based on the dual combination of a reversed flow injection system and a continuous flow system without injection. The performance of the system was optimised by using both an univariate optimisation and a modified simplex method. The method meets the requirements of marine fish farms for monitoring the qual ity of input and output water streams, particularly in terms of simplicity and the high sampling rate allowable. Besides, it has a limit of detection of 3.6 mug L-1 P-PO43- and 19.8 mug L-1 N-NH4+ and relative standard deviat ions (RTSD) of 6.9% and 3.6%, respectively.