|Direct spectrophotometric determination of ammonia in precipitation|In: Tellus. Munksgaard: Copenhagen. ISSN 0040-2826, more
The method is based on the reaction of ammonium nitrogen with hypobromite in an alkaline medium. The excess of hypobromite is determined spectrophotometrically by adding an azo dye (Bordeaux B) solution, which is decolorized by hypobromite in acid solution. The influence of e.g. organic compounds is eliminated by allowing the whole reaction to proceed in acid solution also. The standard curve is a straight line up to 400 micrograms of ammonium nitrogen per liter, and the reaction is sensitive to 10 micrograms per liter, equal to 0.01 ppm, as determined in 25 ml of sample.