How to use agricultural instruments and pesticide quick test cards to detect pesticide residues in vegetables and fruits
How can I use the existing agricultural instruments and pesticide quick test cards to detect the pesticide residues of vegetables and fruits? Shaoxing Wine,Shaoxing Huadiao Daughter Rice Wine,Shaoxing Rice Wine Huangjiu,Shaoxing Huadiao Daughter Rice Wine Zhejiang Shanying Trading Co.,Ltd. , https://www.shanyingtrading.com
A recommended method is as follows:
1 Scope: This method is applicable to the rapid detection of organophosphorus and carbamate pesticides and rodenticides in vegetables, fruits, corresponding foods, water and poisoning residues. This method is taken from the national standard rapid detection method.
2 Detection principle: cholinesterase can catalyze the hydrolysis of indophenol acetate (red) to acetic acid and indophenol (blue), and organophosphorus or carbamate pesticides can inhibit cholinesterase, catalyze and hydrolyze. The process of discoloration changes, thereby judging whether the sample contains residual organophosphorus or carbamate pesticide residues.
3 test materials
3.1 A quick test card for the curing of pesticides with cholinesterase and indophenol acetate reagents.
3.2 ethyl acetate
3.3 pH 7.5 phosphate leaching (buffering) solution: 15.0 g of disodium hydrogen phosphate [Na2HPO4·12H2O] and 1.59 g of potassium dihydrogen phosphate [KH2 PO4] were respectively taken and dissolved in 500 mL of distilled water.
3.4 Weighing balance
3.5 When equipped, the “Pesticide Residue Fast Tester†and ultrasonic extractor designed for the pesticide quick test card are equipped.
4 Detection of pesticide residues in vegetables and fruits, judgment of results and precautions
4.1 Surface measurement method (rough screening method): Wipe off the soil surface of the vegetable, drop 2 to 3 drops of the extract on the surface of the vegetable, and gently rub the other vegetable at the drip. Take a quick test card and drop the drops on the vegetables on the white tablets. Place the reaction for 10 minutes for pre-reaction, fold the quick test card in half (the red pill is overlapped with the white pill), and then pinch it for 3 minutes. When compared with the blank control test card, the white pill does not change color or is slightly light blue. . White pills turned sky blue or the same as blank control cards. When conditions permit, insert the paper into the “Pesticide Residue Tester†for automatic constant temperature and time detection.
4.2 Overall measurement method: Select representative vegetable samples, wipe off the surface soil, cut into square pieces of about 1cm, take 5g into the bottle with lid, add 10mL extract (the ratio of sample to extract is 1+) 2), shake for 50 times (when conditions are available, the extraction bottle can be shaken in an ultrasonic extractor for 30 seconds) and allowed to stand for more than 2 minutes. Take a quick test card, drop 2~3 drops of extract on the white pill, place it for 10min for pre-reaction, fold the quick test card in half (the red pill is overlapped with the white pill), and then pinch it for 3min, open and blank. Compared with the experimental card, the white tablets did not change color or slightly light blue were positive results. White pills turned sky blue or the same as blank control cards. When conditions permit, insert the paper into the “Pesticide Residue Tester†to automatically adjust the temperature and observe it regularly.
4.3 Note:
4.3.1 The test methods for the determination of pesticide residues used at home and abroad (paper method and spectrophotometry) are basically the same, and the interfering substances in the measurement are basically the same. Onion, garlic, radish, celery, coriander, white, mushroom and tomato juice contain plant secondary biomass that has an effect on the enzyme, which is prone to false positives. When handling such samples (including vegetables with higher chlorophyll), do not cut too much. When measuring tomato, the extract can be immersed in the syrup for 2 min, and the soaking solution is taken. When measuring amaranth or garlic, the whole or whole can be placed in a container, and the extract is added and shaken and extracted for measurement.
4.3.2 For the detection of pesticides in drinking water, 2 to 3 drops can be directly added to the quick test card for operation. The detection of pesticides in tea leaves on tea trees can be determined according to the method. For processed tea leaves, refer to "Detection of pesticides in corresponding foods and poisoning residues".
4.3.3 The speed of the test sample The pre-reaction placement time should be as consistent as possible with the blank control card. The time for the red pill to overlap with the white pill is controlled at 3 min, and the time for opening the observation should be within 1 min.
4.3.4 The reason why the blank control card does not change color is that the surface of the tablet may be added less, the surface of the pre-reacted tablet is not wet enough; the second is that the pH of the extract (buffer) may be problematic (purified at this time) The water is confirmed by comparison; the third is that the operating environment may contain pesticide residues in the air.
4.3.5 When determining whether the sample is a positive result of organophosphorus or carbamate pesticides, it should be the result of repeated tests. If necessary, send the sample to the laboratory for further determination of which pesticide is using a gas chromatograph or mass spectrometer. content.
5 Detection of pesticides in relevant foods and poisoning residues, judgment of results and precautions:
5.1 Sample processing and determination: Take the appropriate amount of the sample in the container, add 2 times the amount of ethyl acetate, shake well, let stand, take the clear liquid in the evaporating dish, evaporate the ethyl acetate on the water bath, take 1mL phosphate The extract is dissolved in the residue after evaporation, and 2 to 3 drops of the residue solution are placed on the white tablet of the quick test card, placed for 10 minutes for pre-reaction, the quick test card is folded in half (the red tablet is overlapped with the white tablet), and the hand is pinched for 3 minutes. Open the quick test card and compare it with the blank control quick test card (the quick test card with only the extract liquid on the white pill). The white pill does not change to a strong positive result, and the light blue color is a weak positive result. Sky blue or the same as the blank control card, a negative result.
5.2 Note:
5.2.1 When determining that the sample is positive for organophosphorus or carbamate pesticides, it should be the result of repeated tests. For poisoning residues, the sample must be sent to the laboratory for further determination by gas chromatography or mass spectrometry. Kind of pesticide, exact content.
5.2.2 Other precautions The same as the precautions for the determination of pesticide residues in vegetables and fruits.
6 Quality control of pesticide quick test card
6.1 According to the operation method and precautions, only the pesticide speed test card with pH 7.5 phosphate extract or pure water is strained to blue; 0.3mg/kg dichlorvos or trichlorfon solution can make the pesticide quick test card Positive.
7. Product storage and expiration date: The quick test card is closed for normal temperature and is valid for 1 year. Refrigeration can extend the validity period.