Photometric determination using the indophenol blue method.
Ammonium is a key parameter in water testing, as it can have adverse effects on marine ecosystems if it is at high levels. One major issue is eutrophication, excessive plant and algal growth.1 As a result, determining ammonium levels in effluents is a critical to maintaining aquatic environments. In this application note, ammonium is quantified in effluents with high chemical oxygen demand (COD) using the Spectroquant® photometric system with ammonium test kits.
As the decomposition with the Crack-Sets 10 or 10C (Potassium peroxodisulfate) fails with strongly organic loaded water (criteria: COD content >300mg/l), a pre-decomposition to destroy the organic matrix is advisable, as described below.
Ammonium nitrogen (NH4-N) occurs partly in the form of ammonium ions and partly as ammonia. A pH-dependent equilibrium exists between the two forms. In strongly alkaline solution ammonium nitrogen is present almost entirely as ammonia, which reacts with hypochlorite ions to form monochloramine. This in turn reacts with a substituted phenol to form a blue indophenol derivative that is determined photometrically. Due to the intrinsic yellow coloration of the reagent blank, the measurement solution is yellow-green to green in color.
The method is analogous to EPA 350.1, APHA 4500-NH3 F, ISO 7150-1, and DIN 38406-5.
One of the following test kits is necessary for this analysis:
*not compatible with Move 100
One of the following instruments is necessary for this analysis:
** This analysis pertains to Nova 60A and all legacy Nova instruments (Nova 30 or Nova 60)
Determine with the above-mentioned test kits.
Ammonium content in mg/l NH4-N = analysis value in mg/l NH4-N