Excess nitrogen in effluents can be problematic because it can lead to contamination of groundwater and subsequent environmental problems. One of these issues is eutrophication—excessive growth of algae and plants—which can adversely affect aquatic ecosystems.1 Total nitrogen in effluents consists of both organic and inorganic nitrogen, including ammonium, nitrite and nitrate. As a result, monitoring nitrogen is critical for environmental reasons. Here we describe the photometric determination of nitrate in effluents using the Spectroquant® system and test kits.
Organic and inorganic nitrogen compounds are converted into nitrates according to the Koroleff’s method by treatment with an oxidizing agent in a thermoreactor. In a solution acidified with sulfuric and phosphoric acid, these nitrates then react with 2,6-dimethylphenol (DMP) to form 4-nitro-2,6-dimethylphenol that is determined photometrically. The digestion is analogous to EN ISO 11905-1. The determination of nitrate is analogous to DIN 38405-9.
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:
The content of total nitrogen can be rationally measured after decomposition according to the Koroleff method in the thermoreactor with alkaline peroxodisulfate solution. The method is restricted for the content of organic compounds, expressed as the COD content. For the decomposition of samples in the thermoreactor, the maximum COD concentration must not exceed 300 mg/l. Very slightly oxidizable nitrogen compounds are only partly measured.
The sample, pH 5 - 9, with a COD value smaller than 300 mg/l is treated as per the instructions of the Spectroquant® Nitrogen Cell Test given. The sample is digested in a closed round-cell in the thermoreactor. After digestion the sample must be checked, as specified, for freedom from peroxides; any peroxides present must be destroyed with sodium sulfite.
Determine with the above-mentioned test kits.
Nitrogen (total) content in mg/l N = analysis value in mg/l N
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