Expand knowledge:
Nitrate nitrogen is a common nitrogen-containing compound, which widely exists in soil, water and food. It is one of the nutrient elements needed for plant growth, but excessive nitrate may have adverse effects on human health and ecological environment. Therefore, the measurement and control of nitrate nitrogen is very important. There are many methods to determine nitrate nitrogen, among which phenol disulfonic acid spectrophotometry is the most commonly used one.
This method is simple in operation, high in sensitivity and less in interference, and is suitable for the determination of nitrate nitrogen in various water samples. In phenol disulfonic acid spectrophotometry, it is necessary to collect water samples, add silver sulfate solution to precipitate chloride, and filter to remove it. Then potassium permanganate solution is added dropwise to oxidize nitrite into nitrate. Next, phenol disulfonic acid is added to the treated water sample.
It reacts with nitrate to produce nitrophenol disulfonate, and then reacts with alkaline solution to produce yellow nitrophenol disulfonate tripotassium salt. Finally, the absorbance was measured at 4 10nm and compared with the standard solution. Besides phenol disulfonic acid spectrophotometry, there are other methods to determine nitrate nitrogen. For example, ion-selective electrode method has the advantages of wide measurement range, high sensitivity and less interference.
However, special ion-selective electrode instruments must be used. There is also distillation-titration method, which is suitable for the determination of high concentration nitrate nitrogen, but the operation is complicated. There are two main sources of nitrate nitrogen: natural sources and man-made sources. Natural sources include nitrate in soil washed by rain and released into water, and plants absorb nitrate in soil and enter water with water flow.
Man-made sources include nitrogen fertilizer applied in agricultural activities, human domestic sewage and industrial wastewater. Excessive nitrate may have a negative impact on human health. High concentration of nitrate can cause methemoglobinemia, leading to hypoxia and asphyxia. In addition, nitrate can be transformed into nitrite under the action of microorganisms, which has carcinogenic and mutagenic effects. Therefore, it is very important to monitor and control nitrate nitrogen.
In environmental monitoring, nitrate nitrogen is one of the important indicators of water quality monitoring. Through the determination of nitrate nitrogen in water samples, we can know the pollution status of water bodies and the health status of ecological environment. At the same time, controlling the use of nitrate in raw materials and processing is also very important for food production.
In a word, the determination of nitrate nitrogen is of great significance to environmental monitoring, food safety and human health. We need to strengthen the research and improvement of its determination method, improve the accuracy and reliability of the determination, and make contributions to the protection of human health and ecological environment safety.