Development of a fully automated inorganic nitrogen analyzer for continuous, unattended monitoring of water quality

A fully automated spectrophotometric analyzer for continuous, unattended determination of inorganic nitrogen (nitrite, nitrate, and ammonia) was developed. The analysis involves online UV photo-induced conversion of nitrate to nitrite and chemical oxidation of ammonia to nitrite. In both cases, nitrite was then subsequently determined by spectrophotometry using the sulfanilamide and N-1-naphthyl-ethylenediamine color reagents. Experimental conditions investigated to optimize the determination of nitrate and ammonia are presented. The linear ranges of the methods for nitrate and ammonia are 0.01–14 ppm and 0.01–5 ppm, respectively. The proposed method is simple, low cost, and sensitive. The analyzer was operated automatically and unattended for a period of 30 days.