Chemiluminescent flow-injection analysis of nitrates in water using on-line ultraviolet photolysis Original Research Article

A sensitive, fast and non-toxic flow-injection method for the chemiluminescent determination of trace amounts of nitrate in water is presented. Nitrate is on-line reduced to nitrite due to absorption of UV light at quartz capillaries and formed nitrite is instantly determined as peroxynitrite by the chemiluminescent reaction with luminol. An UV photo-reductor consisting of a high-pressure mercury lamp and two quartz capillaries provides an effective reduction of nitrate even though only deionized water as a carrier is employed. Efficiency of nitrate conversion to nitrite is 56±3%. The detection limit of nitrate is 4×10−9 M (0.248 μg/l). Linear range of the method is 8×10−9 to 1×10−5 mol/l of nitrate. Cations and common anions do not interfere. Analysis time is 6 min. The method was applied to the determination of nitrate in various real water samples. The results are in a good agreement with a reference chromatographic method.