Discussion on the determination of total phosphorus in industrial circulating water
Thread Content
For the determination of total phosphorus in national standard industrial circulating water, sodium sulfite is not added when the sample solution is boiled until it is almost dry. When measuring total phosphorus in our unit some time ago, no color development occurred; after consulting some literature and finding that sodium sulfite is used in such cases, we added 1 ml of it, and color development was achieved. I would like to ask whether it is necessary to add it at all, and what the purpose of adding sodium sulfite is
During the digestion of samples for total phosphorus determination, a strong oxidizing agent (persulfate) is added in order to convert organic phosphines into inorganic phosphate ions. However, since an excess of oxidant is added, and a reducing agent is required in the process of forming phosphomolybdic blue color, it is under acidic and reducing conditions that the yellow color of phosphomolybdic heteropolyacid is converted to blue. Therefore, after sample treatment, a certain amount of reducing agent must be added; sodium sulfite can be used, or stannous chloride can also be added.
Thank you, Professor. So it needs to be done under reducing conditions