Whats the principle of the in-line total nitrogen digestion?
Nitrogen compounds are oxidized in-line to nitrate using alkaline persulfate/UV digestion. Oxidation of nitrogen-containing compounds to nitrate is achieved at 90°C with additional energy supplied by UV light. The digestion occurs prior to the injection valve. Results for wastewater samples with settleable solids may be up to 20% low when compared with a rigorous off-line digestion. If effluent samples are acid preserved, in-line digestion results will match manual off-line digestion. Results for the samples without settleable particulates, such as surface water and sea water, will match the manual off-line digestion. This should be validated with a typical sample before reporting results. After digestion, nitrate is quantitatively reduced to nitrite by passage of the sample through a copperized cadmium column. The nitrite (reduced nitrate) is then determined by diazotization with sulfanilamide under acidic conditions to form a diazonium ion. The diazonium ion is coupled with N-(1-naph
