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[Detection significance]
Pesticide residue refers to the total name of trace pesticide progenitors, toxic metabolites, degradation products and impurities that remain in organisms, agricultural by-products and the environment after the use of pesticides.
Because of the more serious pests and diseases during the growth of vegetables, the amount of pesticides used is relatively large.
Enzyme inhibition rapid tester method, its detection basis is GB/T 5009.
[Sampling location]
Farmer's markets and large supermarkets are the two main vegetable sales channels, and the sources and types of vegetables sold are diverse
[Experimental reagents and materials]
(1) Extraction solution Pour the extraction solution powder into a 500mL bottle, add 510mL distilled water and shake to dissolve it for later use
(2) Enzyme Solution Add 3.
(3) Substrate Add 3.
(4) Chromogenic agent The chromogenic agent is already in the brown bottle, directly add 64 mL of the extract and shake well, then put it in the refrigerator at 4°C for later use
(5) The samples were from farmers' markets and supermarkets in 3 districts and counties, and commonly used vegetables were selected according to 6 categories of leafy vegetables, fruit vegetables, edible fungi, cauliflower, stem vegetables and root vegetables
[Experimental Instruments and Equipment]
(1) NCD-100A multifunctional agricultural product safety analyzer (Shanghai Ruixin Technology Instrument Co.
(2) Pipette gun (10~100uL, 200~500μL, 1~5μL) and its matching nozzle;
(3) Supporting glass instruments and accessories, electronic balance
[experimental method]
After booting, select the pesticide residue module, and select the main wavelength of 410nm in the project settings) After the parameter setting is completed, enter the sample test, and click the hole position you want to set as the test sample after the layout, and the sample number will automatically increase from 1 and display in the hole position.
(1) The preparation method of the control solution: Use a pipette to extract 200uL of the extract into the enzyme-labeled hole (the hole that shows B), and then use the pipette with a new pipette tip to extract 20uL of enzyme solution and 20uL of the indicator to the setting The good one corresponds to the microtiter plate hole (showing hole B)
(2) Sample preparation method
①Take the vegetables with clean surface, use a balance to accurately weigh 1g, take the leaf part of leafy vegetables, and take the surface of melons and fruits
②Cut the leaves or melon skin meat into 1cm square size and place them in a small beaker, add 5mL extraction solution with a pipette to soak, and leave it at room temperature for 10min) while stirring several times
③After the extract in the beaker settles slightly, use a pipette to draw 200μL of the supernatant (that is, the test solution) and transfer it into the corresponding sample well
④Add 20μL of enzyme solution and 20μL of color reagent into the sample well into which 200μL of test solution is placed
.
(3) Determination
Place the above-prepared control solution and sample solution (semi-finished products) for 15 minutes (it is recommended to incubate in a constant temperature incubator at 37°C).
When the time is up, use an 8-channel pipette to add 20uL of substrate to each well and mix, immediately Put the ELISA plate into the instrument, close the cover, and press the start button to start the test
.
The test result will be displayed after the two board passes, and click the result button to display the test result
.
At the end of the test, the difference in absorbance is displayed.
Click the Result button to view the result, and the result of the inhibition rate is displayed
.
[Result judgment]
The test result is expressed by the degree of enzyme inhibition (inhibition rate), inhibition rate=(ΔA 0 -ΔA 1 )/A0 X 100%, where,
ΔA 0 ——The change in absorbance of the control solution after reacting for 3 minutes;
ΔA 1 ——The change in absorbance of the sample solution after reacting for 3 minutes
.
When the inhibition rate is ≥50%, it means that there are high-dose organophosphorus or carbamate pesticides in the vegetables, and the sample is a positive result, which is unqualified
.
When the inhibition rate is less than 50%, it means that there are low-dose organophosphorus or carbamate pesticides in the vegetables, and the sample is negative and judged as qualified
.
Related links: rapid detection of arsenic, antimony, bismuth, and mercury compounds