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Key words: The preliminary detection techniques of organophosphorus pesticide residues are limited to chemical method, colorimetric method and bioassay. The detection method lacks specificity and the sensitivity of test paper is not high. The application of gas chromatography in the analysis of pesticide and drug residues in 1960s greatly improved pesticide and drug residues?

abstract:

The early detection techniques of organophosphorus pesticide residues are limited to chemical methods, colorimetry and bioassay, and the detection methods lack specificity and sensitivity. The application of gas chromatography in the analysis of pesticide and drug residues in 1960s greatly improved the detection level of pesticide and drug residues. Since 1980s, high performance liquid chromatography (HPLC) has been widely used to analyze thermally unstable and ionic pesticides and their metabolites. Although chromatography has accurate quantification and high sensitivity, it needs expensive equipment and professional operation, and the analysis time is long, which is not conducive to on-site monitoring. In this paper, the research progress of rapid detection and analysis technology of pesticides and drug residues is reviewed. The research on the detection technology of 1 luminescent bacteria shows that the luminescent mechanism of different kinds of luminescent bacteria is the same [1]. That is to say, through the action of molecular oxygen and the catalysis of intracellular luciferase, the reduced FMNH2 and long-chain fatty aldehydes are oxidized into FMN and long-chain fatty acids, and blue-green light with the maximum luminous intensity of 450 ~ 490 nm is released at the same time. Commonly used luminescent bacteria are some bacteria of Vibrio and Photobacterium. Yuan Dongxing [2] and others used luminescent bacteria to quickly detect organophosphorus pesticide residues in vegetables. Through the photoinhibition reaction of luminescent bacteria to several organophosphorus pesticides in vegetables, it was found that the luminous intensity was negatively correlated with the concentration of organophosphorus pesticides in the samples, and the minimum detection limit could reach 3 mg/L. At present, the detection technology of luminescent bacteria is widely used in environmental monitoring and food safety detection, mainly for the detection of pesticide residues and heavy metal biotoxicity [3]. This method is rapid, simple and sensitive. However, after being activated, the luminous intensity of luminescent bacteria will change with time, which will lead to unstable detection results. In addition, due to the complex ingredients in food and the low concentration of pollutants, the detection instrument can not reach such a low detection limit, so this method is rarely used in food safety detection. Chemiluminescence technology Chemiluminescence (CL) is a very chemical reaction between luminol, gallic acid and organophosphorus pesticides. The intermediate or reactant of the reaction absorbs the chemical energy released by the reaction and jumps to the excited state. When they return from the excited state to the ground state, they emit optical radiation. After passing through the photomultiplier tube and amplifier, photons are converted into current and amplified. Under certain conditions, the current is directly proportional to the concentration of organophosphorus pesticides [4] According to the reaction principle, there are four detection methods: (1) CL method for acetylcholinesterase inhibition; (2) alkaline phosphatase catalytic chemiluminescence method; (3) the method of reaction between peroxide and indole; (4) The method of reaction between luminol and hydrogen peroxide (H2O2). The detection limit of organophosphorus pesticides by chemiluminescence method can reach ng/kg level. Ayyagari [5] detected dimethoate according to the fact that alkaline phosphatase can catalyze dephosphorization of phosphorus-containing compounds, that is, dimethoate inhibits the activity of phosphatase and produces a weak luminescence signal, with the detection limit of 500 ng/L. Rao Zhiming [6] and others analyzed the chemiluminescence of organophosphorus pesticide-methyl parathion by using luminol -H2O2 system, and found that polyethylene glycol had a significant sensitizing effect on the reaction. A flow injection chemiluminescence (FIA-CL) method for the determination of parathion methyl was established, with the detection limit of 0. At present, chemiluminescence, immunoassay, molecular imprinting, microfluidic chip and other technologies are used to detect pesticide and veterinary drug residues in food [7], but they are still in the laboratory stage and are rarely used in practice. Chemiluminescence technology has the advantages of high sensitivity, fast reaction speed, good selectivity and simple equipment, which is more suitable for on-site monitoring. 3 Immunoassay Techniques The immunoassay techniques used for pesticide residue analysis mainly include radioimmunoassay (RIA) and enzyme-linked immunoassay (EIA). Due to the limitation of RIA in the requirements of instruments and equipment, EIA has become one of the most widely used technologies for pesticide residue analysis. EIA has direct method, indirect method, antibody sandwich method, competition method and inhibition method in practical application. Immunoassay is a method based on the specific recognition and binding reaction of antigen and antibody. Organophosphorus pesticide is a small molecular weight pesticide (MW% 26lt2500). It is necessary to prepare artificial antigen by valence bond coupling of small pesticide molecules in hapten form with a carrier with a certain carbon chain length and a large molecular weight (generally protein), and to immunize animals with the artificial antigen to produce antibodies (polyclonal antibodies) with specific reaction to pesticides, and to prepare antibodies (monoclonal antibodies) with single antigen specificity by hybridoma technology. Ma Kumar et al [8] used enzyme-linked immunosorbent assay (ELISA) and flow injection technology to detect methyl parathion in environment and food, with high sensitivity and good specificity. The linear concentration range of carbaryl enzyme immunoassay developed by Liu et al [9] in China is10-1~10-4 μ g/ml, and the detection limit is lower than 00 1 ng/ml. Wang Gangduo [10] and others synthesized the artificial antigen of methyl parathion, and established an ELISA analysis method with a detection limit of 5 ng/ml. At present, immunoassay technology is mainly aimed at pesticide and veterinary drug residues in food and environment. It is reported that ELISA detection methods have been established for hundreds of pesticides, such as carbendazim, carbofuran, paraoxon, parathion and methyl parathion. The detection limit of some organophosphorus pesticides can reach ng or even pg level, and some kits have been commercialized, which are widely used for rapid monitoring of field samples and a large number of samples [1 1, 12]. Up to now, 1 kit can only detect a single organophosphorus pesticide, but can't detect multiple pesticide residues, and there is a certain degree of overlap between compounds with similar structures. In addition, the preparation of antibody is difficult and the cost of kit is high, which limits its wide application in pesticide residue detection. 4 Biosensor technology Biosensors usually refer to analytical tools that are closely matched by biosensors and converters to produce selective and reversible responses to specific kinds of compounds or bioactive substances [13- 16]. When an object to be detected is specifically combined with a molecular recognition element (composed of biologically effective substances with recognition ability, such as enzymes, microorganisms, antigens, antibodies, etc.), the generated light and heat are converted into exportable electrical signals and optical signals by a signal converter, which are processed by a detector through electronic technology and displayed or recorded on an instrument, thus achieving the purpose of detection and detection. 4 1 enzyme biosensor The active site of organophosphorus pesticide irreversibly binds to the ester group of acetylcholinesterase, thus inhibiting the activity of enzyme. The pH value change caused by enzyme reaction is detected by potentiometric biosensor. Its advantages are rapid, accurate and reusable, but the enzyme has high specificity to substrate and poor stability. Bernabeil M coupled several enzymatic reactions on a biosensor to increase the number of analytes, that is, an amperometric H2O2 sensor for detecting paraoxon and aldicarb was prepared by using acetylcholinesterase and choline oxidase. 42. Immunobiosensors are biosensors that utilize the immunochemical reaction between antibodies and antigens. It can detect pesticide residues in samples with high sensitivity, high selectivity and convenience. Wan [17] and others developed a portable optical fiber immunosensor to detect parathion methyl, and its minimum detection limit was 0. 1 ng/ml. Compared with chromatography, the optical fiber immunosensor developed by Anis et al. is used to determine parathion in samples. This method is simple and rapid, and the analysis period is shortened by 4/5. Microbial sensors use the metabolic efficacy of living microorganisms to detect pollutants, one is the respiratory efficacy of oxygen consumed by microorganisms when assimilating substrates; The other is to use different microorganisms containing different enzymes as enzyme sources. Its advantage is that it can adapt to a wide range of pH and temperature, but its selectivity is poor. Mulchandani et al. transformed the plasmid carrying the gene fragment of organophosphorus hydrolase (OPH) into a Moraxella strain, and screened out an improved strain that can express OPH extracellular, so that the detection limits of the prepared sensor for methyl parathion and paraoxon can be as low as L× 10-6 mol/L and 2×10-7 mol/L [/kloc-]. Biosensors have been widely used in environmental monitoring, food, medicine and other fields. Compared with other analytical techniques, biosensor has the advantages of small size, low cost, strong selectivity and anti-interference ability, fast response speed, and can also detect multiple samples at the same time with high sensitivity. However, there are still some new problems in biosensor technology, such as poor stability and short service life. Prospect of pesticide residue detection at present: Photobacterium technology is mainly used for water quality detection and environmental planning. With the development of technology, photobacterium phosphoreum method will be combined with electronic technology and photoelectric technology, and gradually developed into an online monitoring system, providing a faster detection and analysis means for on-site monitoring of organophosphorus pesticides. Chemiluminescence method is a highly sensitive detection and analysis technology for trace organophosphorus pesticide residues developed in recent years. In the future, new luminescent reagents and their combination with other technologies (such as microfluidic chip technology and sensor technology) will be synthesized while improving and perfecting the original luminescent reagents and systems. ) shows the advantages of CL, which is fast, sensitive and simple. At present, ELISA technology and biosensor technology are still in the primary stage. With the continuous improvement of analytical technology, ELISA has reduced the occurrence of cross-reactions, further improved the sensitivity and stability, and the immune kit has been commercialized. The versatility of biosensor (1 sensor can detect a variety of pesticide residues) will reduce product cost, improve sensitivity, stability and prolong service life. They will be further applied and popularized in the field of pesticide residue detection, which will make the application of rapid detection technology of pesticide residue in China more diversified. Refer to [1] thomtdakw. 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