Detection steps

1. Cut the sample into pieces, weigh 1 gram into a sample cup, add 20 milliliters of distilled water (or purified water) into the sample cup, let it sit for 10-15 minutes, and stir the sample a few times during this time;

2. Add 2ml of distilled water (or purified water) to the colorimetric dish, and then use a pipette to draw 1 tube of liquid from the middle of the sample cup (i.e. 0.5ml of sample extract) into the colorimetric dish;

3. 3 drops each of detection solution A and detection solution B, shake well, and after 2 minutes, observe the color under natural light;

Color development steps for standard samples (30mg/kg provided as needed)

1. Add 2ml of distilled water (or purified water) to another colorimetric dish;

2. Then add 1 drop of standard substance;

3. Add 3 drops of detection solution A and 3 drops of detection solution B in sequence, shake well;

4. After two minutes, it should display a very light purple red color.

Result judgment

Observe the color in the sample colorimetric dish and compare it with the color chart to determine. It can also be compared with the color development results of the standard sample. If the sample shows a clear purple red color and is darker than the standard color or the corresponding 30mg/kg color on the color chart, it means that the nitrite content of the sample exceeds the standard by 30mg/kg. The deeper the purple red color displayed on the sample, the higher the content. During operation, it should be noted that the color development time of the standard and sample solutions should be as similar as possible. The specific content can also be compared with the color chart, and the color closest is the corresponding nitrite content. The regulations on nitrite limits vary for different types of samples. Please refer to the relevant standards in Article 2 for specific compliance.

Note: Standard products will be slowly oxidized by air, and the concentration will gradually decrease. To use standard products as a control, please use them within one month of leaving the factory. After expiration, please use a color chart for comparison.

Composition of speed test box (specification: 100 times/box)

1. Detection frequency: 100 times;

2. Testing solution A: 2 bottles (green cap);

3. Testing solution B: 2 bottles (blue cap);

4. Disposable straws: 100 pieces;

5. Disposable sample cups: 100 pieces;

6. Colorimetric dish: 2 pieces

precautions

1. The sample size is 1 gram, try to be as accurate as possible;

2. When sampling meat products, lean meat or other edible representative parts should be taken;

3. Samples that exceed the standard should be retested once to confirm;

4. The regulations on nitrite limits vary for different types of food, and attention should be paid to the limit standards when making judgments.

5. The concentration of standard products will gradually decrease with the increase of storage time, and should be used within one month after leaving the factory. Please compare with a color chart after the expiration date;

6. The experimental water shall not use tap water, deionized water or mineral water; Distilled water should be used;

7. After use, the colorimetric dish should be rinsed with water multiple times in a timely manner, then washed with distilled water and dried for later use.

8. Extract the sample solution and add distilled water using 5000 μ l and 1000 μ l pipettes as much as possible to improve detection accuracy.

9. After adding the reagent, please observe for 2 minutes and compare it with the color chart (samples containing nitrite will darken over time).