Pesticide residue testing is an important part of ensuring the quality and safety of agricultural products. Do you know what pesticide residue testing methods are? In supermarkets, farmer's markets and quality supervision, pesticide residue detectors are commonly used to carry out pesticide residue detection. So what are the detection methods and principles of pesticide residue detectors? This article answers one by one.
1. Detection methods of pesticide residues (8 types)
1. Spectroscopy This method is based on chemical reactions such as oxidation, sulfonation, esterification, and complexation of certain functional groups or hydrolysis, reduction products and special color developers in organophosphorus pesticides under specific conditions to produce colors with specific wavelengths. Reaction to carry out qualitative or quantitative (limit) determination.
2. Chromatography (1) Thin layer chromatography (TLC)
Thin-layer chromatography is a mature and widely used method for rapid detection of trace amounts. It has its unique use in pesticide residue determination technology. It is not only an important separation method, but also a qualitative and quantitative analysis method.
In the detection process, organophosphorus pesticides are generally extracted with a suitable solvent, purified and concentrated, separated and expanded on a thin-layer silica gel plate, and then compared with standard organophosphorus pesticides for Rf value for qualitative determination or quantitative determination with instruments.
(2) Gas chromatography (GC)
The method uses the extracted, purified, and concentrated organophosphorus pesticides to be injected into the gas chromatographic column. After programmed temperature rise and vaporization, different organophosphorus pesticides are separated in the solid phase, and the gas chromatogram is drawn by different detectors. It is qualitative by retention time, and quantified by comparing the peak or peak area with the standard curve. It can measure multiple components at the same time, which is simple and quick, with high sensitivity and good accuracy. The optimal setting of chromatographic conditions is the key to gas chromatography technology.
(3) High performance liquid chromatography (HPLC)
High performance liquid chromatography is a chromatographic analysis method developed on the basis of liquid chromatography column chromatography, introducing the theory of gas chromatography and improving it. The application of high performance liquid chromatography in the analysis of pesticide residues has become more and more extensive, because high performance liquid chromatography can be suitable for the analysis of high boiling point and not easy to vaporize, thermally unstable and strongly polar pesticides and their metabolites; and can be used with The combination of pre-column extraction, purification and post-column fluorescence derivatization reaction and mass spectrometry makes it easy to realize automation of analysis; at the same time, the advent of some new detectors has improved the detection sensitivity of high performance liquid chromatography to a certain extent. Compared with gas chromatography, it not only has good separation efficiency, high sensitivity, fast detection speed, but also has a wide range of applications.
3. Chromatography-mass spectrometry combined with chromatography-mass spectrometry technology not only exerts the high separation ability of chromatography, but also exerts the high identification ability of mass spectrometry, which can perform qualitative and quantitative analysis of multiple residues at the same time. , Especially suitable for multi-residue analysis. GC-MS is currently a more mature and widely used color-mass spectrometry technology. It not only has the high separation performance of gas chromatography, but also has the characteristics of accurate compound structure identification by mass spectrometry. It can achieve the purpose of simultaneous qualitative and quantitative detection. It is mostly used for pesticides. Detection of metabolites and degradation products and multi-residue detection.
4. Capillary electrophoresis In the past, pesticides were mostly determined by HPIE and GC methods, but recently they can be separated and determined by CE. The separation mode mainly uses CZE and capillary micellar electrokinetic chromatography (MEKC). Capillary electrophoresis has been used for the determination of pesticide residues in foods such as milk, beer, grains, fruits, vegetables and pork.
5. Immunoassay technology The application of immunoassay technology in pesticide residue detection includes radioimmunoassay and enzyme immunoassay. At present, the application research of enzyme immunoassay technology, especially enzyme-linked immunoassay in pesticide residue detection, is very active abroad, and its application is also Increasingly common.
ELISA is a detection method based on the specific and reversible binding reaction of antigen and antibody, and its detection level can reach ng or even pg level. ELISA is widely used in the analysis and detection of pesticide residues in food such as organophosphorus pesticides, organochlorine pesticides, herbicides, carbamate pesticides, veterinary drug residues (such as chloramphenicol), mycotoxins, etc. As a rapid screening method, the EKSIA method often suffers from false positives when analyzing complex matrix samples due to matrix interference and cross-linking reactions. Therefore, if you need to quantify and verify the sample, other analytical methods are needed.
6. Enzyme inhibition method Enzyme inhibition method is the most studied and relatively mature technology for rapid detection of some pesticide residues. Enzyme inhibition method is widely used to determine pesticide residues. Acetylcholinesterase is more sensitive to organophosphorus pesticides, with high sensitivity and selectivity, but it is expensive, and some pesticides do not inhibit it significantly, and additional oxidation is required. Additives or pretreatments to improve the sensitivity of pesticide detection. So some people study the use of butyrylcholinesterase and animal and plant esterase instead of acetylcholinesterase. By screening a large number of plants, Yu Jicheng and others initially obtained a source of plant enzymes with higher activity, and used enzyme inhibition to quickly detect trichlorfon, parathion and other organophosphorus pesticide residues in vegetables.
7. Biosensor A biosensor assembled with a film of immobilized AChE and a pH electrode was used to determine the residues of organophosphorus and carbamate pesticides. At present, the development and application of biosensor method is a research hotspot in pesticide residue detection technology. Great progress has been made in diversifying measurement methods, improving measurement sensitivity, shortening response time, improving instrument automation, and adapting to on-site detection capabilities.
The biological substances used in the biosensors used to study the detection of pesticide residues are mainly enzymes, whole cells, organelles, receptors or antibodies, etc. Correspondingly, there are enzyme sensors, whole cell sensors and immunosensors. Especially the application of immunosensors can be greatly improved. Improve the detection sensitivity and greatly shorten the detection time. The optical fiber sensor, the product of the combination of biosensor and optical fiber technology, has broad application prospects in rapid detection and online detection.
8. Living body detection method Living body detection method is a technology that uses living organisms to carry out bioassays. For example, the effect of pesticides and bacteria can affect the luminous intensity of bacteria, and the luminous intensity of bacteria can be used to detect pesticide residues. However, this method only responds to a few pesticides, and cannot distinguish the types of residues, and the accuracy is low. The sensitive housefly detection method is to feed the housefly with a sample and determine the pesticide residue based on the mortality of the housefly.
The technical method is straightforward, simple in process, easy to master, and users can detect on their own without complicated instruments. The disadvantage is that the detection time is long, the qualitative is rough and the accuracy is low. Humans and animals may be different, which affects the judgment of pesticide residues.
2. Detection method of pesticide residue detector
The pesticide residue detector detection method actually uses the enzyme inhibition method, which is the sixth method above. The pesticide residue detector can achieve qualitative analysis and help determine whether the pesticide residues in agricultural products exceed the standard. If it is necessary to achieve quantitative analysis, that is, it exceeds the standard. How much, what is the actual content, you need to adopt other testing methods or testing equipment. However, the general screening of pesticide residues in the main areas has been able to meet the needs of this instrument, which can greatly reduce the occurrence of pesticide residue accidents, effectively ensure the quality and safety of agricultural products, and ensure the safe circulation of various agricultural products.
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