Pesticide Residue Rapid Detection Technology The enzyme inhibition method is a method for rapid detection of pesticide residues using the toxicological properties of organophosphorus pesticides. Under certain conditions, organophosphorus pesticides have a certain inhibitory effect on the normal functions of some of the enzymes in the catalytic hydrolysis. The inhibition rate is positively correlated with the concentration of pesticides. These include enzymes from various animal sources, acetylcholine and choline as well as phytoeneases extracted from certain plants. Let the enzyme react with the sample extract or solution. If there are no pesticide residues in the sample or the residue is minimal, the enzyme activity will not be inhibited and the hydrolysis reaction will not be affected. On the other hand, if the pesticide residue is high, the enzyme activity will be Is inhibited by pesticides, and then through the detection of some specific color, pH or current changes, so as to achieve the purpose of detecting organophosphorus pesticides. The enzyme inhibition method mainly includes a colorimetric method, a speed measurement card (sheet) method, and a biosensor method.
1. Chemical rapid measurement method (speed measurement method)
The chemical rapid measurement method is mainly based on a rapid detection method for determining the redox properties of organic phosphorus pesticides. Organophosphorus pesticides (phosphoric acid, dithioic acid, and phosphoric acid amines) are hydrolyzed into phosphoric acid and alcohols by the action of a metal catalyst, and the hydrolysis product reacts with the detection solution to change the purple color of the detection solution to a colorless solution. The disadvantage of this method is that it is only limited to organophosphorus pesticides, its sensitivity is not high, and it is easily interfered by some reducing substances. The advantage is that the instability of the enzyme is avoided, the operation is simple, the price is low, the detection speed is fast, and the reagents are further improved. Performance, standard measurement technology, can improve the sensitivity and accuracy of detection, and thus favored by the vast majority of urban and rural agricultural product producers and sellers.
2. Colorimetry Colorimetry is the most commonly used method for the rapid detection and determination of pesticide residues in the enzyme inhibition method, and it is also the simplest one. The iodine thiocholine iodide formed by the enzyme hydrolysis of the substrate iodinated acetylcholine can interact with 5,5-dithio-2,2-dinitrobenzoic acid (DINB) to generate 5 -1 Based on a 2-nitrobenzoic acid (yellow). The colorimetry was performed at the characteristic wavelength (420.0 nm), the absorbance was measured, and the degree of inhibition of cholinesterase was calculated based on the degree of change in the absorbance over a certain period of time. The regression was established by regression analysis with the concentration of the pesticide. The equation is a method for determining the amount of residual pesticide in a sample by determining the inhibitory rate of the unknown sample against enzyme activity. Using this method to determine the pesticide residues in vegetables, fruits and agricultural products, high sensitivity, simple operation, rapid inspection, can detect a variety of pesticide residues. At present, the majority of domestic pesticide residue testers use the principle of color change (absorbance) to study design. The instruments developed by different companies are very similar, except that some use acetylcholine acetylcholine, and some use tyrosine choline base enzyme, there are differences in the application of enzymes and substrates, and thus determine the inhibition rate is also different.
3 speed card method Fast card method is also known as enzyme film method. The acetylcholine-base enzyme or other similar enzymes and the acetylcholine analogue, NPA, were separately solidified and then loaded on a filter paper to form a small card. The application of this simple carrier technology can achieve the purpose of portability and on-site operation. Since American scientists invented the enzyme tablet technique in 1985, Chinese scholars have also conducted a lot of research and developed the matching pesticide residue fast-measuring cell technology. The box is equipped with self-made enzyme tablets, color reagents and substrate tablets. All the required vessels and reagents, which do not require expensive equipment, equipment and professional technical operators, can be used directly in the field and give information on whether there is pesticide residue directly by means of the color reaction.
1. Chemical rapid measurement method (speed measurement method)
The chemical rapid measurement method is mainly based on a rapid detection method for determining the redox properties of organic phosphorus pesticides. Organophosphorus pesticides (phosphoric acid, dithioic acid, and phosphoric acid amines) are hydrolyzed into phosphoric acid and alcohols by the action of a metal catalyst, and the hydrolysis product reacts with the detection solution to change the purple color of the detection solution to a colorless solution. The disadvantage of this method is that it is only limited to organophosphorus pesticides, its sensitivity is not high, and it is easily interfered by some reducing substances. The advantage is that the instability of the enzyme is avoided, the operation is simple, the price is low, the detection speed is fast, and the reagents are further improved. Performance, standard measurement technology, can improve the sensitivity and accuracy of detection, and thus favored by the vast majority of urban and rural agricultural product producers and sellers.
2. Colorimetry Colorimetry is the most commonly used method for the rapid detection and determination of pesticide residues in the enzyme inhibition method, and it is also the simplest one. The iodine thiocholine iodide formed by the enzyme hydrolysis of the substrate iodinated acetylcholine can interact with 5,5-dithio-2,2-dinitrobenzoic acid (DINB) to generate 5 -1 Based on a 2-nitrobenzoic acid (yellow). The colorimetry was performed at the characteristic wavelength (420.0 nm), the absorbance was measured, and the degree of inhibition of cholinesterase was calculated based on the degree of change in the absorbance over a certain period of time. The regression was established by regression analysis with the concentration of the pesticide. The equation is a method for determining the amount of residual pesticide in a sample by determining the inhibitory rate of the unknown sample against enzyme activity. Using this method to determine the pesticide residues in vegetables, fruits and agricultural products, high sensitivity, simple operation, rapid inspection, can detect a variety of pesticide residues. At present, the majority of domestic pesticide residue testers use the principle of color change (absorbance) to study design. The instruments developed by different companies are very similar, except that some use acetylcholine acetylcholine, and some use tyrosine choline base enzyme, there are differences in the application of enzymes and substrates, and thus determine the inhibition rate is also different.
3 speed card method Fast card method is also known as enzyme film method. The acetylcholine-base enzyme or other similar enzymes and the acetylcholine analogue, NPA, were separately solidified and then loaded on a filter paper to form a small card. The application of this simple carrier technology can achieve the purpose of portability and on-site operation. Since American scientists invented the enzyme tablet technique in 1985, Chinese scholars have also conducted a lot of research and developed the matching pesticide residue fast-measuring cell technology. The box is equipped with self-made enzyme tablets, color reagents and substrate tablets. All the required vessels and reagents, which do not require expensive equipment, equipment and professional technical operators, can be used directly in the field and give information on whether there is pesticide residue directly by means of the color reaction.
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