Vegetable pesticides rapid measurement methods and precautions
Among the chemical pesticides used in vegetable production, there are the most varieties, the largest amount, and the most likely to cause poisoning are organophosphorus insecticides. At present, the application of the Shanghai CL-1 Residual Pesticide Tester in Hunan Province can quickly detect pesticide residues in vegetable products, as described below. First, GL-1 pesticide residue rapid detection method 1. Instrument normal working conditions (1) room temperature 25-35 °C (above 25 °C room temperature, add water bath). (2) The indoor relative humidity is not more than 85%. 2. Reagent preparation (1) Diluent 2 bottles of diluted powder are mixed in the bottle, and 100 mL of distilled water is added to shake. (2) Enzyme solution Each bottle of enzyme solution plus 5.2mL diluent was shaken and set aside in a 4°C environment. The prepared enzyme solution can be used for 7 days at 4°C. (3) Reagent: Mix 2 bags of color reagent in the bottle, add 32mL of diluent, shake it, and set it in a 4°C environment for later use. (4) Substrate Add 5.2mL of distilled water to each bottle of substrate powder. Shake it well and store it in a 4°C environment. The prepared substrate solution can be stored for 3 days at 4°C, and frozen for 5 days. (5) Extracting solution After mixing 2 bags of extract powder, place it in a 500 mL brine bottle and add 510 mL of distilled water to shake and reserve. Note that powders attached to enzymes, substrates, etc., must be kept in the freezer below 0°C in the refrigerator (valid for 1 year). 3. Preparation of test solution (1) 2 - 2.5 kg of edible dishes were picked from the field and divided into 3 parts, 1 part for record, 1 part for re-inspection and 1 part for detection. Take clean vegetables on the surface, accurately weigh 1g with the balance, take leaves from the leafy vegetables, cut fruit and vegetables such as tomatoes and cucumbers. (2) Cut the leaves and melons into 1cm squares, place them in a small beaker, add 5mL of the extraction liquid, and let it stand at room temperature for 20 minutes. Shake the beaker every 3 minutes. (3) Pour the extract from the beaker into a test tube. After slightly sedimenting, suck the supernatant 2.5mL with a pipette and transfer it to another tube. This is the test solution. 4. Instrument operation and test (1) When the power is turned on, when the digital tube counts down from “1200†to “0â€, the warm-up ends and the instrument automatically enters the standby state. (2) Adjust the instrument to “0â€: Place the black rectangular block into the colorimetric cell, cover the sample cell cover, and press the “0†key, the instrument will display “000.0â€. (3) Adjust the instrument "100": Place the empty cuvette in the instrument cell, and press the "100" key to display the instrument as "100.0". (4) "Control" test: Take 2.5mL extract plus 0.1mL enzyme solution and 0.1mL color reagent, mix, put at room temperature for 15min immediately after mixing 0.1mL substrate, immediately poured into the cuvette, press "Control" button, after 3min "control" indicator light off, press "display" button to show the control absorbance value. (5) "Sample" test: Take 2.5mL of the test solution by adding 0.1mL enzyme solution and 0.1mL color reagent in the test tube and mix, after 15min at room temperature, immediately add 0.1mL substrate and mix, immediately poured into the cuvette , into the colorimetric pool, press the "sample" button, 3min after the "sample" indicator light off, press the "display" button to get the sample absorbance value and sample inhibition rate. (6) Discrimination criteria for test results If the measured enzyme inhibition rate is less than 50%, it is safe fruit vegetables. Inhibition rate equal to or higher than 50% is a pesticide residue toxicity super standard. Second, pay attention to matters 1. In the preparation of the liquid preparation, leaching should be shaken every 3min, shaking and non-angular effects. The leaching time must be guaranteed to be 20 minutes. Shortening the time has a greater impact on the results. 2. It is recommended to use the same cuvette (wash with distilled water 2 times before each use, then spin dry, and wipe dry with glossy paper). Using different cuvettes has a great influence on the results. A batch of samples tested at the same time, sharing a control, is also conducive to shorten the working hours. 3. The reaction time of the enzyme liquid and the coloring agent and the extract solution is 15 min. The reaction time is different. The result is different. The longer the time, the higher the sensitivity. 4. The enzyme and color reagent cannot be added or added excessively, otherwise it will have a great influence on the result. In the process of detecting vegetable samples, serious and serious procedures should be followed. It is suggested that more than 50% of the samples should be qualitatively and quantitatively analyzed by chromatography or mass spectrometry to determine whether the pesticide residues are really Excessive standards. 5. For onions, garlic, leeks, taro, taro, and other vegetables, the use of enzyme inhibition test speed, there is a great possibility of false positive, and the more spicy flavor of garlic varieties, the higher the frequency of false positives, but not Found that the test process has a false negative problem. 6. The purple eggplant, tomato, red pepper, red leeks, and sponge gourd contain natural pigments, and are juicing, and are rapidly detected by the enzyme inhibition method. The results are not disturbed by pigments and juices. For the cold vegetables, spinach, celery, etc. in the green leafy vegetables, the results of the enzyme inhibition test were normal, and false positives and false negatives were unlikely. 7. The test results only play a supervisory role. This method only performs coarse screening on pesticides containing organophosphorus and carbamate pesticides, and has no effect on the detection of other pesticides. Therefore, in sales management, it should strengthen the Moral education, strictly in accordance with the pollution-free vegetable technical regulations, use any pesticides that are allowed to use, must go to the market after the safety interval, so as not to cause adverse effects of food. 8. Spinach, pakchoi, beans, etc. are mandatory inspection items, because these types of vegetables or pesticide residues, or the use of pesticides are numerous and dense. However, the detection of other types of vegetables must not be overlooked. 9. The original records of sampling, test results, etc. should be properly prepared and printed on a computer, which is convenient for archiving and for future reference. China Agricultural Network Editor