Excessive nitrite can cause bleeding and is an important factor in inducing fulminant diseases. When it is higher than 0.5, it can cause fish to get sick or die. In the fishery standard, the concentration of nitrite is 0-0.02mg/L, ammonia nitrogen Ammonia nitrogen at a concentration of 0-0.02mg/L will damage the gills of fish and mussels. If it is higher than 0.5, it will cause inability to eat and breathe until death.
Determination of nitrite in water:
Nitrite test steps:
①Take a clean colorimetric tube, add the water sample to be tested to the 15mL scale line, and add a pack of N02-(1).
②Add one pack of NO2 -(2) after 5 minutes and shake well.
③ Perform visual color comparison after 10 minutes. For color comparison, lift the colorimetric tube to about 1 cm from the blank space of the colorimetric card to visually compare the color from top to bottom.The standard color gradation with the same color tone as 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 will cause interference by generating precipitation,
Determination of nitrate in water:
1. Take out a test strip and quickly close the lid
2. Partially immerse the reaction area in the test solution for 10 seconds, and remove the excess water droplets
3. After standing for 3 minutes, compare the color with the color chart, and the color close to the color block is the density value.
1. Cover the lid immediately after removing the test paper to prevent the test paper from oxidizing and turning to moisture
2. If there is an error in the test result, measure whether the PH value of the tested liquid is 5-9, and the tested liquid is colorless
3. Color comparison at the specified time. Excluding the second case, the test result is objectionable, check whether there is interference.
Nitrite 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 pure water to be tested;
3. Add the purified water to be tested to the scale line of the sample tube, add a pack of 10030 reagent, cover the lid and shake to dissolve, 5 minutes later add-pack of 10040 reagent, shake to dissolve. After 10 minutes, put the standard tube and sample tube on a white background and visually compare the color from top to bottom. If the color of 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 is unqualified.
Nitrite in food:
1. When the vegetables are placed at room temperature, the internal compound of the vegetables is sterile, but its own enzymes 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 to produce nitrite. The so-called overnight vegetables and leftovers are harmful. On the one hand, stale vegetables will produce nitrite. On the other hand, if the vegetables are not eaten in time after cooking, they will also produce nitrite.