Analytical Chemistry Optical Chemosensor for Spectrophotometric Determination of Nitrite in Wastewater

An easy, sensitive, and rapid spectrophotometric method has been documented for determining nitrite (NO2-) in water and wastewater. To detect and adsorb harmful nitrite ions from wastewater efficiently; a stable optical nanosensor was manufactured by immobilization of 1-Naphthylamine (1-NA) over mesoporous silica nanospheres (MSNs). The determination of nitrite was based on the reaction of nitrite with the optical sensor (1-NA chemosensor) and forming diazonium salt which was subsequently coupled with N-(1-Naphthyl) ethylenediamine dihydrochloride (NED) to form a stable brownish azo dye. The dye shows an absorption maximum at 457 nm. The optimal conditions for the reaction and the analytical parameters were evaluated. The method has been designed by controlling the acidity, the quantity of reagents required and the amount of tolerance of certain ions. The range of linearity was found to be 0.108-10.8 mu M of nitrite. The nitrite identification detection limit and quantitation limit are 0.106 mu M and 0.353 mu M, respectively. The performance of the chemosensor in extracting the NO2- ions was tested. According to the Langmuir isotherms, the adsorption pattern was highly competent, where the removal capacity for NO2- ion was 156.0 mg/g by the chemosensor. Some cations and anions have been identified as the competing ions; these ions were not affected on the NO2- ion in both detection and adsorption processes.