1. China's national standard uses ammonium molybdate spectrophotometry to determine the total phosphorus content in water. The basic principle of this method is that under acidic conditions, phosphorus in water samples reacts with ammonium molybdate to generate ammonium phosphomolybdate, and then it is reduced to molybdenum blue. Finally, the concentration of total phosphorus is calculated by measuring the absorbance.
2. Specific experimental steps: Collect a certain volume of water sample and add appropriate amount of sulfuric acid to make it acidic. Add an appropriate amount of ammonium molybdate solution to make it react with phosphorus in the water sample to generate ammonium phosphomolybdate. Let the reacted solution stand for a period of time, and then add an appropriate amount of bismuth nitrate solution to make it undergo a reduction reaction to generate molybdenum blue.
3. Measure the absorbance of molybdenum blue with spectrophotometer, compare it with standard curve, and calculate the concentration of total phosphorus in water sample. It should be noted that the experimental conditions and operation steps should be strictly controlled during the experiment to ensure the accuracy and reliability of the experimental results. At the same time, in order to reduce errors and interference, the quality of experimental water and reagents must be strictly controlled.
The role of mass total phosphorus determination
1. Water pollution assessment: Total phosphorus is one of the important indicators reflecting the eutrophication degree of water bodies. Measuring the total phosphorus content in water can help us understand the pollution situation of water and judge whether it is in a state of excessive nutrient load.
2. The increase of total phosphorus content is usually related to pollution problems such as algae reproduction and water quality deterioration. Therefore, the determination of total phosphorus in water quality is of great significance for evaluating the health status of water body and formulating corresponding control measures.
3. Monitoring the effect of sewage treatment: In the process of sewage treatment, phosphorus is one of the important pollutants. Through the determination of total phosphorus in the inlet and outlet water quality of sewage, the operation effect of sewage treatment plant can be effectively monitored and the phosphorus in sewage can be effectively removed. This has an important guiding role for the operation, management and improvement of sewage treatment plants.
4. Guiding water environment management: In the management of natural water bodies such as rivers and lakes and artificial water bodies such as reservoirs, the determination of total phosphorus in water quality can help managers understand the content of nutrients in water bodies and guide managers to formulate reasonable water environment management measures. For example, by monitoring the total phosphorus content, parameters such as water level and flow rate can be adjusted to promote the self-purification ability of water bodies.
5. Early warning function: The determination of total phosphorus in water quality plays an important role in early warning of possible algae outbreaks and cyanobacterial toxin release in water bodies. When the total phosphorus content continues to increase, it may mean that the risk of algae reproduction in water bodies increases, and managers need to take timely measures to intervene to prevent water quality deterioration and fish death.