In the water quality, plant decay, fish excrement excrement, etc. will produce ammonia, nitrogen is the main element of protein, mainly in the atmosphere, organisms and minerals. Digestive bacteria will convert ammonia into nitrite and nitrate. Nitrate is a nutrient for plant growth, it will promote the growth and development of plants, and will lead to the growth of algae.
Excessive nitrite can cause hemorrhagic disease, which is an important factor that induces fulminant disease. When it is higher than 0.5, it will cause disease or death of fish. In the fishery standard, the concentration of nitrite is 0-0.02mg/L, ammonia nitrogen Concentration of 0-0.02mg/L ammonia nitrogen is too high will damage the gills of fish and mussels, above 0.5 will cause inability to eat and breathe until death.
Determination of nitrite in water:
Nitrite test steps: ① Take a clean colorimetric tube, add the water sample to be measured to the 15mL scale, and add a packet of N02-(1). ② After 5 minutes, add one more package of NO2-(2) and shake well. ③ After 10 minutes, visually compare the colors. For colorimetry, lift the colorimetric tube to a space approximately 1 cm away from the colorimetric card and visualize the colorimetry from top to bottom.The standard color scale that is the same as the color tone of the solution in the tube is the content of nitrite in the sample (mg /L).
1) Various strong oxidants and reducing agents can cause interference.
2) Cu2+, Fe2+ and nitrate make the measurement result low.
3) Metal ions such as lead, mercury and silver can cause interference by generating precipitation,
Determination of nitrate in water:
1. Remove a test strip and quickly close the lid
2. Immerse part of the reaction zone into the test solution for 10 seconds, take out and throw off excess water beads
3. After being left for 3 minutes, compare the color with the color card, and the color close to the color block is the density value.
1. After removing the test paper, you need to close the cover immediately to prevent the test paper from oxidizing and turning into moisture
2. If the test result has errors, measure whether the PH value of the liquid under test is 5-9, and the liquid under test is colorless
3. Color comparison at the specified time. Excluding the second case, the test results are objected to see if there is interference.
Determination of nitrite in purified water:
On September 24, 2003, the "Sanitary Standards for Drinking Water in Bottles (Barrels)" (GB 19298-2003) was released. The standard stipulates that nitrite (NO2~) 1 (mg/L) in drinking water in bottles (barrels) should be ≤0.005mg/L.
Nitrous acid concentration detection kit (for purified water):
1. Transfer all the solution in the small plastic tube in the standard tube to the standard tube, dilute to the mark with distilled water, and keep the solution in the tube until the reagents in the kit are used up;
2. Rinse the sample tube with the pure water to be tested;
3. Add the pure water to be tested to the scale of the sample tube, add a pack of 10030 reagent, close the lid and shake to dissolve. After 5 minutes, add a pack of 10040 reagent and shake to dissolve. After 10 minutes, place the standard tube and sample tube on a white background and visually compare the color. If the sample tube solution is lighter than the standard tube solution, the nitrite content in the purified water to be tested is qualified (less than 0.002mg /L) Otherwise, it fails.
Nitrite in food:
1. When the vegetable is placed at room temperature, the inner part of the vegetable is sterile, but its own enzyme will reduce nitrate and produce nitrite;
2. After the vegetables are cooked, their own enzymes are killed, but the bacteria multiply, and hundreds of bacteria can produce nitrate reductase, thereby producing nitrite. The so-called overnight vegetables and leftovers are harmful. On the one hand, it means that fresh vegetables will produce nitrite. On the other hand, if vegetables are not eaten in time after cooking, they will also produce nitrite.