Determination of chlorite in water by resonance scattering spectrometry with Methylene blue

In CH3COONa-HCl buffer solution, ClO2- oxidizes excess I- to generate I3-, and I3- forms complex particles with positively charged methylene blue under electrostatic attraction, which enhances the resonance scattering intensity of the system. Based on this principle, a new method for the determination of trace NaClO2 in water by resonance scattering spectroscopy was established.The measurement conditions of this method were optimized to improve the resonance scattering intensity. The optimal dosage of CH3COONa-HCl buffer solution, KI solution, and methylene blue solution, as well as the optimal reaction time and measurement wavelength, were obtained during the measurement. Under the optimal conditions, the resonance scattering intensity increased with the increase of ClO2- mass concentration in the range of 0.018 2-0.364 0 mg/L, which showed a good linear relationship with a detection limit of 0.004 8 mg/L. When this method was used to determine the content of chlorite in groundwater, the relative standard deviation of the measurement results was 1.5%-2.9%, and the recovery rate was 96%-99%.