Determination of nitrite nitrogen in water by UV-1100 spectrophotometry

This method is used to determine the concentration of nitrite nitrogen in water samples using a spectrophotometric technique known as diazotization coupling. The procedure involves a series of chemical reactions that produce a colored compound, which can be measured at a specific wavelength. Key components include: - A spectrophotometer (such as V-1100 or V-1200 models) - Reagents like p-aminobenzenesulfonamide and N-(1-naphthyl)-ethylenediamine hydrochloride - A 1 cm cuvette and distilled water as a reference Procedure: 1. If the water sample is turbid or dark, take 100 ml and add 2 ml of aluminum hydroxide suspension. Stir and let it settle before filtering. 2. Adjust the pH of the sample to neutral if necessary, then measure out 50.0 ml into a colorimetric tube. 3. Add 1 ml of p-aminobenzenesulfonamide solution (10 g/L) and let it stand for 8 minutes. Then add 1.0 ml of N-(1-naphthyl)-ethylenediamine hydrochloride solution (1.0 g/L), mixing immediately. 4. Measure the absorbance at 540 nm after 10 minutes using pure water as the reference. 5. Calculate the nitrite nitrogen concentration using the formula: C_NO2-N = M / V Where: - C_NO2-N is the nitrite nitrogen concentration in mg/L - M is the nitrite nitrogen content from the calibration curve (in µg) - V is the volume of the water sample in mL This method is widely used in environmental analysis for monitoring water quality and ensuring compliance with safety standards.