Imultaneous catalytic spectro-photometric determination of nitrite and nitrate in flour and water with flow injection analysis

摘要

The nitrate content is an important factor for environmental water samples and flour. In a 0.35 mol/L H_2SO_4 solution, NO_2- has a strong catalyzing function on the decolourization of Gallocyanine (GC) oxidated by NaBrO_3. Based on this, a novel method was developed to measure the NO_2-and NO_3- concentrations in water and flour. The flow injection technology was introduced into the analysis system. A single-valve dual-cingulums to inject which the Copperized-Cadmium slice and the reduction zone are isolated. The optimum solution for this method contains 1.48x10 - 4 mol/L GC, 0.06 mol PL NaBrO_3 and 0.2 mol/L of NH_4Cl. Two empirical equations were proposed to calculate the NO_2-and N03- concentrations based on the measured signals. It can be used to measure NO_2 - of from 0.001 mg/L to 2. 6 and NO_3 - of from 0.002 mg/L to 3. 6 mg/L. The measurement frequency can be up to 20 samples/h. The relative standard deviation for eleven samples is less than 5%.