SPECIATION OF NITROGEN IN WASTE-WATER BY FLOW-INJECTION

A rapid method for the sequential determination of nitrite, nitrate an d total nitrogen is proposed. Nitrite was determined directly by using the Griess reaction, which was also used to quantify nitrate after re duction to nitrite with hydrazine. For total nitrogen determination, t he nitrogen-containing compounds (organic substances and nitrite and a mmonium ions) were oxidized photochemically using a UV lamp and conver ted into nitrate, which was then reduced to nitrite and determined spe ctrophotometrically. Under the optimized conditions, up to 220 mu mol l-1 N-NO2- and 240 mu mol l-1 N-NO3- can be determined, the detection limits being 2 mu mol l-1 N-NO2- and 8 mu mol l-1 N-NO3-. The relative standard deviation for nitrite and nitrate are 1.5 and 2.3%, respecti vely. The photo-oxidation method for total nitrogen determination has a linear range of 30-1000 mu mol l-1 N, with a relative standard devia tion of 3%. The proposed method was applied to the determination of ni trate, nitrite and total nitrogen in wastewaters.