Total phosphorus in circulating water

I think it’s this: after heating and evaporating the liquid, white smoke begins to emerge from the bottle (it’s probably sulfuric acid smoke); at that point, the heat should be reduced. Otherwise, the result will be low, as the decomposition is incomplete!

This post was last edited by qugd on 2012-6-21 at 11:30: 1. Evaporate it until it is almost dry – acid fumes will be emitted, but there will still be visible liquid at the bottom of the bottle. Such judgment can only be developed by conducting more experiments to gain experience. 2. If it is not heated to the required degree, some of the organophosphorus compounds may not be completely decomposed, resulting in lower values for the total phosphorus measurement. This situation occurs less frequently, usually due to a short heating time or insufficient temperature. 3. If overheating occurs, resulting in the emission of large amounts of acidic smoke, the volatility and polymerization properties of phosphorus pentoxide can also lead to lower values in the determination of phosphate levels in the sample.

Has anyone on the 3rd floor experienced this: when calibrating the total phosphorus curve, after leaving it there for a few minutes, turbidity occurs and it affects colorimetry? Low concentrations result in little or no turbidity, while high concentrations lead to significant turbidity.

This situation may be due to the presence of a certain amount of metal ions in the sample, particularly calcium. Additionally, the sample can be appropriately diluted, as the sensitivity of the phosphomolybdenum blue colorimetric method is relatively high; diluting the sample can help to prevent turbidity to a certain extent.

It can also be boiled and heated for 10 minutes to achieve more stable data. ! ! ! ! ! ! ! !

(Boiling it first and then heating for 10 minutes also yields more stable data.) ! ! ! ! ! ! ! ! ) When we were working with the curves, we observed turbidity; the results were the same whether heating was applied or not.

I have a method for determining the total phosphorus content in circulating water; potassium persulfate needs to be added along with sulfuric acid, and we boil the solution for half an hour. During this process, distilled water must be added continuously to keep the solution at a certain level

During cooking, distilled water needs to be added continuously to maintain a certain liquid level; we didn’t do that. We control the time so that only 10 milliliters of solution remain; glass beads are added to prevent splashing. The temperature of the electric furnace is also controlled to avoid drying out the solution, and if it dries out, the process must be repeated.

Pay close attention; heat it until just white smoke appears, otherwise it will affect the accuracy of the measurement results. . .

We use GB/T 6913-2008, \"Determination of total phosphate content\" – Section 5.1: Method summary. In an acidic solution, potassium persulfate is used as a decomposing agent to convert polyphosphates and organic phosphines into orthophosphates. These orthophosphates react with ammonium molybdate to form a yellow phosphomolybdantimonate complex, which is then reduced to phosphomolybdan blue using ascorbic acid. The concentration is determined by spectrophotometry at the maximum absorption wavelength of 710 nm. The reaction is as in 3.1; reagents and materials are as in 4.2 and the following reagents. 5.2.1 Potassium persulfate solution: 40 g/L. Weigh 20 g of potassium persulfate, with an accuracy of 0.5 g, dissolve it in 500 mL of water, stir well, and store it in a brown bottle. The validity period of this solution is 1 month. 5.3 Instruments and Equipment 5.3.1 Spectrophotometer: equipped with an absorption cell with a thickness of 1 cm. 5.4 For the analysis steps, refer to Appendix A: Transfer an appropriate volume of the sample (3.4.1) into a 100 mL beaker, and add 1.0 mL of sulfuric acid solution (1+35) to reduce the pH value to below 1. 5.0 mL of potassium persulfate solution (40 g/L), brought to a gentle boil for nearly 30 min. While boiling, add water as needed to keep the volume between 25 mL and 30 mL, then cool it. Adjust the pH to 3–10 using a sodium hydroxide solution (80 g/L), then transfer it to a 50 mL volumetric flask. Add 2.0 mL of ammonium molybdate solution (100 g/L) and 1.0 mL of ascorbic acid solution (26 g/L), dilute to the mark with water, mix well, and allow to stand at room temperature for 10 min. At 710 nm in a spectrophotometer, with a 1 cm cell, the absorbance was measured by zeroing with the blank. During the testing process, if some of the interferences listed in Appendix B occur, corresponding measures can be taken to eliminate them.