New detector tube for the detection of nitrite in water

A new colorimetric detector tube for the detection of trace concentrations of nitrite in water was developed. The detector tube is based on a diazo coupling reaction of nitrite with dapsone and N-(1-naphthyl) ethylenediamine dihydrochloride during the formation of red-violet azo dye. Spherical granules (pellets) made from the composite material were used as the carrier of chemical reagents. They were prepared by pelletizing the mixture of microcrystalline cellulose, lactose, kaolin and polyvinylpyrrolidone. Colouring is done on a layer of silica gel impregnated with citric acid. The detector tube is highly sensitive, selective and stable when stored. The detection limit is 0.1 μg.ml^-1, i.e. 0.03 μg.ml^-1 N(NO₂ -). The optimal measuring range of nitrite concentration in the analyzed sample ranges from 0.5 to 80 μg.ml^-1, i.e. 0.15-24.36 μg.ml^-1 N(NO₂ -). The detector tube can easily be structurally modified for analysis of nitrates with a detection limit of 1 μg/ml^-1, i.e. 0.23 μg.ml^-1 N(NO₃ -).