Nitrite mainly refers to sodium nitrite, which is white to light yellow powder or granular, slightly salty and easily soluble in water. Its appearance and taste are similar to salt, and it is widely used in industry and construction. Meat products are also allowed to be used as color developers in limited quantities. The probability of nitrite causing food poisoning is very high. Eating 0.0.5g of nitrite will lead to poisoning and even death. The main causes of acute poisoning are: 1. Mistake nitrite for salt, flour alkali, etc. 2. Doping, fraud. 3. Poisoning. 4. Eat vegetables containing a lot of nitrite. Especially for stale leafy vegetables, the causes of chronic poisoning (including canceration) are: 1. Drinking well water with excessive nitrite content. 2. Eating meat products with excessive nitrite content. Therefore, the determination of nitrite content is a very important item in food safety inspection.

Methods According to the principle of GB/T 5009.33, the rapid measuring tube was made and compared with the standard color card.

operational approach

1. Rapid detection of nitrite in table salt and rapid identification of table salt and nitrite: Take 1 flat spoon of table salt, use the spoon attached in the bag, add it into the detection tube, add distilled water or purified water to the scale of 1ml, cover it, shake it evenly to dissolve the solid part, and compare it with the standard color plate after 10 minutes. The value on the color plate multiplied by 10 is the content of nitrite in salt mg/ kg (the national standard stipulates that the limit of nitrite in salt (refined salt) should be ≤2 mg/kg). When the sample appears blood red, produces precipitation or rapidly fades to Huang Shi, it can be judged that the nitrite content is quite high, or the sample itself is nitrite.

2. Liquid sample detection: directly take 1ml clarified liquid sample, add it into the detection tube, cover it, shake the dissolving reagent evenly, and compare it with the standard colorimetric plate after 10min to find out the colorimetric standard with the same color as the solution in the detection tube. The value on the color scale is the content of nitrite in the sample mg/L (calculated by sodium nitrite). (Milk and soybean meal can also be directly detected, and the results shall not exceed.

3. Detection of solid or semi-solid samples: put the evenly crushed samples 1.0g or 1.0ml to 10ml into a colorimetric tube, add distilled water or deionized water (purified water) to the scale, shake well, and take the supernatant (or supernatant obtained by filtration or centrifugation)1. After 10 minutes, compared with the standard color swatch, the value on the color swatch multiplied by 10 is the content of nitrite in the sample mg/ kg, L (calculated as NaNO2). If the test result exceeds the highest value on the color plate, it can be quantitatively diluted before determination. When calculating the result, multiply it by the dilution multiple (for example, take 1.0mL from 10ml colorimetric tube and transfer it to another 10ml colorimetric tube, add water to the scale, and take 1.0mL from it and add it to the detection tube for determination. Multiply the test result by 100 (double dilution) to get the content of nitrite in the sample.

Description: ① Drinking water often contains trace amounts of nitrite, which cannot be used as a diluent for determination. (2) If the color is very dark, there is precipitation after color development or it quickly fades to light yellow, indicating that the nitrite content in the sample is very high, and the dilution multiple should be increased for re-determination. (3) Repeat the experiment for the samples exceeding the standard, and send the samples to the laboratory for accurate quantification when conditions permit.