Abstract
A sequential injection analysis system has been developed for on-line monitoring of nitrite and nitrate in wastewaters, based on the Griess-Llosvay reaction and spectrophotometrical measuring of the absorbance at 543 nm. Nitrate is previously reduced to nitrite in a copperized cadmium column and analyzed as nitrite. The proposed system is fully automatized and is able to monitor nitrite and nitrate, simultaneously, in samples at a frequency of about 24 samples per hour with a relative standard deviation (RSD) better than 2.0% for nitrite and 1.3% for nitrate. The calibration graph was linear between 0.05 - 25 mg dm-3 for nitrite and 0.05 - 15 mg dm-3 for nitrate.
