Methods of identifying invalid pesticides

Identify from the form of pesticides

1. Powder The wettable powder should be loose powder with uniform color. If the original powdered pesticide has agglomerated and is not easily crushed, it is invalid.

2. Emulsifiable concentrate should be a homogeneous liquid, without precipitation or suspended matter. If there is turbidity, or the emulsion diluted with water is not uniform or has oil slick or sediment, it means that there is a quality problem.

3. Suspending agent The suspending agent should be a flowing suspension liquid without agglomeration. There may be a small amount of delamination in long-term storage, but it can be restored to its original state after shaking.

4. If the fumigation tablet is in powder form, it has expired.

5. The aqueous agent should be a homogeneous liquid without sediment or suspended matter. Generally, there will be no turbid sedimentation after being diluted with water.

6. Granules The product should be granules of uniform thickness and should not contain a lot of powder.

2. Use simple methods to check physical and chemical properties

1. Wettable powder The first is the water test method: first take about 200 ml of clean water, then take 1 g of the pesticide to be tested, and sprinkle the pesticide on the water gently and evenly, and observe carefully. The pesticides that are wet and soluble in water within 1 minute are non-expired pesticides, otherwise they are ineffective pesticides. The second is the stirring method: take 40-50 grams of the pesticide to be tested, put it in a glass container, add a small amount of water to make a paste, and then add 150-200 ml of water, stir well, and let it stand for 10 minutes and observe. Pesticides that have not expired have good solubility, and the suspended powder particles in the drug solution are fine, otherwise the pesticide has expired. Three heating method: Take 5-10 grams of the tested pesticide and heat it on the metal. If white smoke is produced with a strong pungent smell, it means that the medicine is good, otherwise, it has expired.

2. Emulsifiable concentrates One is the shaking method: For pesticides with oily water layers, shake the bottle vigorously, then let it stand for 1 hour and observe. If there is still stratification, it means that the medicine has deteriorated and has become invalid. The second is the heating method: put the pesticide with the sediment in the bottle and put it in 50~60℃ warm water, observe after 1 hour, if the sediment slowly dissolves, it means that the medicine has not expired; if the sediment is difficult to dissolve or does not dissolve , Indicating that the medicine has expired. The third is the dilution method: take 50ml of the pesticide to be tested, put it in a glass bottle, add 150ml of water, shake vigorously and let it stand for 30 minutes. If the drug solution is uniform and milky white, and there is no slick on the top and no precipitation on the bottom, it means The medicine is good, otherwise it is invalid pesticide.

3. Dry suspending agent Dry suspending agent means that it can be self-dispersed after being diluted with water. The original drug is dispersed in water with particles with a particle size of 1 to 5 microns to form a relatively stable suspension.

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