The pretreatment technology and detection methods of pesticide residue analysis at present are reviewed. In sample pretreatment, solid phase extraction, supercritical fluid extraction

Boundary fluid extraction and matrix solid phase dispersion extraction have been rapidly developed and widely used. Supercritical fluid chromatography and liquid chromatography-mass spectrometry

Detection methods such as biotechnology, immunoassay, direct spectrometry and biosensor have broad application prospects.

Keywords: pesticide residue; Analysis; pretreatment

China Library Classification Number: S 48 1.8 Document Identification Number: A Document Number:1002-2767 (2005) 03-0027-03.

Overview of the development of pesticide residue analysis technology

Shi Feng De, Wang Bo, Qu Hongjie

(Heilongjiang Bayi Agricultural University Daqing 1633 19)

Abstract: The methods of pretreatment and detection of pesticide samples were introduced.

At present, cide remains. Solid phase extraction, supercritical fluid extraction and matrix solids.

-Phase dispersion extraction technology has developed rapidly and is widely used in sample pretreatment-

ment。 Supercritical fluid chromatography, liquid chromatography-

Mass spectrometry, immunoassay, direct spectroscopy and biosensor.

Keywords: pesticide residue; Analysis; pretreatment

The use of pesticides has undoubtedly greatly improved the yield of crops, but the ensuing environmental pollution problem has also attracted great attention. Many countries in the world have stipulated the limits of various pesticide residues in food and grain. Strengthening pesticide residue monitoring and environmental toxicology research is of great theoretical and practical significance for rational development and correct use of pesticides, protecting ecological environment, safeguarding human health and avoiding and reducing unnecessary agricultural losses [1]. In recent years, with the development and application of ultra-efficient pesticides and the increase of samples to be tested, more stringent requirements have been put forward for the sensitivity, specificity and rapidity of pesticide residue analysis technology. Therefore, some new advanced pesticide residue analysis techniques have emerged. In this paper, some analysis and detection methods of pesticide residues are reviewed.

1 sample pretreatment technology

Modern analytical methods of pesticide residues usually include sample pretreatment and determination. Before the determination of pesticide residues, there should be pretreatment steps such as extraction, purification and concentration suitable for the physical and chemical properties of various samples. These pretreatment processes usually play an important role in the analysis. At present, the commonly used extraction and purification methods include rinsing method, homogenization method, Soxhlet extraction method, ultrasonic extraction method, liquid-liquid distribution method, column chromatography, thin layer chromatography and so on. Since 1990s, some new sample pretreatment techniques have been introduced into pesticide residue analysis. These new technologies are characterized by saving time, reducing labor intensity, saving solvents, reducing sample consumption, improving extraction or purification efficiency and improving automation level. At present, the new technologies that have been reported or widely used mainly include: solid phase extraction (SPE), solid phase microextraction (SPME), supercritical fluid extraction (SFE), molecularly imprinted synthetic receptor technology (MISR) and so on.

1. 1 solid phase extraction (SPE)

Solid phase extraction (SPE) is a sample pretreatment method based on liquid chromatography separation mechanism, which has been widely used in pesticide residue detection. According to the principles of liquid phase separation, analysis and concentration. After the sample solution mixture passes through the chromatographic column, a component in the sample remains in the chromatographic column, and the residual component is eluted by selecting a suitable solvent, so as to achieve the purpose of separation and purification. Solid-phase extraction overcomes the shortcomings of liquid-liquid extraction (LLE) and ordinary column chromatography, and has the characteristics of high efficiency, simplicity, rapidity, safety, good repeatability and convenient pretreatment automation. According to the packing in the column, it can be divided into adsorption type (such as silica gel and macroporous adsorption resin). ), distribution type (C8, C 18, phenyl column, etc. ) and ion exchange type. According to the properties and sample types of the pesticides to be tested, the extraction, enrichment and purification can be completed in one step by selecting appropriate microcolumns, eluents and other optimization conditions [2].

1.2 supercritical fluid extraction (SFE)

Supercritical fluid extraction (SFE) is a special separation technology developed in recent years. SFE is an extraction method which mainly uses supercritical fluid instead of various solvents to extract the components to be detected in the sample. At present, the most commonly used supercritical fluid is CO2, which has both gas permeability and liquid distribution. CO2 in the effluent volatilizes under normal pressure, and the analyte is analyzed after being dissolved in the solvent. Supercritical CO2 is nontoxic and its molecular polarity is relatively small, so it can be used to extract nonpolar or weakly polar pesticide residues. You can also add a proper amount of polarity regulator, such as methanol, to adjust its polarity, so as to maximize the extraction of pesticide residues with different polarities and minimize the extraction of impurities. It is characterized by avoiding the use of a large number of organic solvents, improving the selectivity of extraction, reducing the analysis time and realizing the automation of operation. SFE technology is one of the fastest developing analytical technologies at present.

1.3 matrix solid phase dispersion extraction technology (MSPDE)

Matrix solid-phase dispersion extraction is a brand-new extraction technology first proposed by Professor Barke of Louisiana State University from 65438 to 0989 and expounded in theory. The basic operation is to directly grind and mix the sample with an appropriate amount of reverse filler (C 1 4 or C 1 8) to obtain a semi-dry mixture, then use it as filler to load the column, and then wash the column with different solvents to elute various substances to be detected. MSPDE is a simple and efficient extraction and purification method, which integrates the processes of sample homogenization, tissue cell lysis, extraction and purification required in traditional sample pretreatment [3]. It is suitable for the extraction and purification of pesticide residues with various molecular structures and polarities, and has been widely used for the detection of pesticide residues in vegetables and fruits.

1.4 molecularly imprinted synthetic receptor technique (MISR)

The principle of molecular imprinting synthetic receptor technology (MISR) is as follows: firstly, the molecules or polymer monomers to be imprinted are bonded, then the polymer monomers are crosslinked, and the imprinted molecules are extracted from the polymer, leaving the imprint of the imprinted molecules inside the polymer. Due to the need to synthesize imprinted molecular derivatives, this technology is limited because some compounds cannot be derived. Molecular imprinting technology can be used to separate drugs, hormones, protein, pesticides, amino acids, polypeptides, carbohydrates, coenzymes, nucleic acid bases, sterols, paints, metal ions and other compounds.

2 detection method

2. 1 gas chromatography

Gas chromatography is a classical analytical method. Using the different distribution coefficients of each component in the sample between the gas phase and the stationary liquid phase, when the vaporized sample is brought into the chromatographic column by the carrier gas, each component is repeatedly distributed between the two phases, separated from each other after a certain column length, and then leaves the chromatographic column in turn and enters the detector. After the generated ion current signal is amplified, the chromatographic peaks of each component are depicted on the recorder. Because of its simple operation, high analysis speed, high separation efficiency, high sensitivity and wide application range, 70% of pesticide residues are detected by gas chromatography at present. Using gas chromatography, a variety of pesticides can be completely separated by one injection, qualitative and quantitative, and then equipped with high-performance detectors, which makes the analysis faster and the results more reliable. At present, gas chromatography mostly adopts packed capillary.

2.2 high performance liquid chromatography (HPLC)

High performance liquid chromatography is also a traditional detection method. It can separate and detect ionic pesticides with strong polarity and large molecular weight, and is especially suitable for the detection of pesticides that are not easy to gasify or decompose when heated. In recent years, the combination of high-efficiency chromatographic column, high-pressure pump, high-sensitivity detector, pre-column or post-column derivatization technology and computer has greatly improved the detection efficiency, sensitivity, speed and operation automation of liquid chromatography, and has now become an indispensable and important means for pesticide residue detection.

2.3 Supercritical fluid chromatography (SFC) technology

Supercritical fluid chromatography is a separation and detection technology with supercritical fluid as chromatographic mobile phase [1]. Various types of long chromatographic columns can be used to analyze compounds with large molecular weight, thermal instability and strong polarity at low temperature. It comprehensively utilizes the advantages of meteorological chromatography and high performance liquid chromatography, overcomes their respective disadvantages, and can be connected with most GC and HPLC detectors, such as FID, FPD, NPD and MS [4]. This greatly broadens its application range, and many pesticides that need to be derivatized by GC or HPLC can be directly determined by SFC.

2.4 Direct spectral analysis technology

Near infrared attenuated total reflection spectroscopy (NearIS-ATR) and surface enhanced Raman spectroscopy (SERS) improved the sensitivity of spectral analysis by 102~ 107 times. These fast and direct spectroscopic techniques only need a few samples and have great application potential. A series of laser spectroscopy techniques such as laser Raman spectroscopy make the sensitivity of spectral analysis almost reach the limit-the level of a molecule or atom. This will provide a possible technical basis for the development of high sensitivity detectors. At present, these high-sensitivity spectral technologies need further research and development before they can enter the stage of wide application.

2.5 capillary electrophoresis (CE)

Capillary electrophoresis is a separation technology developed on the basis of electrophoresis technology. Its working principle is to make different charged particles (ions, molecules or derivatives) in the capillary directionally migrate in the background buffer at different speeds under the action of high-pressure field, so as to realize separation. According to the different functions of sample components in background buffer, capillary electrophoresis can be divided into capillary zone electrophoresis (CZE), capillary gel electrophoresis (CGE), isoelectric focusing (IEF), micellar electrokinetic chromatography (MEKC), isotachophoresis (ITP) and so on. Since Jorgenson applied E to analytical chemistry in 1980s, this technology has developed into one of the most active fields in separation science. It has the advantages of high sensitivity, low cost, less sample consumption (only nano-upgrade per injection), high separation column efficiency and convenient use. It is very suitable for the separation and analysis of ionized samples that are difficult to separate by traditional liquid chromatography, and its separation efficiency can reach one million theoretical plates. At present, capillary electrophoresis still lacks a highly sensitive detector. Therefore, only by researching and developing a more sensitive detection system can we give full play to the advantages of this technology.

2.6 liquid chromatography-mass spectrometry (LC/MS)

Liquid chromatography-mass spectrometry (LC-MS) is a detection technology that connects liquid chromatography and mass spectrometry in series into a complete machine. Used to analyze pesticides with low concentration, difficult volatilization, thermal instability and strong polarity. LC/MS has successively produced four interface technologies: thermal spray (TSP), particle beam (PB), electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI). At present, an internal injection and particle flow interface technology connects liquid chromatography with mass spectrometry, which has been successfully used to analyze compounds that are unstable to heat, have large molecular weight and are difficult to analyze by gas chromatography. It has the advantages of high detection sensitivity, good selectivity, simultaneous qualitative and quantitative analysis and reliable results. LC-MS can purify simple samples before analysis and has almost universal multi-residue analysis ability. It has obvious advantages in online confirmation of a positive sample. Although LC/MS instrument is expensive and the interface technology between liquid chromatography and mass spectrometry is not very mature, it is still an efficient and reliable analysis technology with great application value.

2.7 immunoassay (IA)

Immunoassay is an analytical method based on the specific recognition and binding reaction of antigen and antibody [5]. Pesticides with large molecular weight can directly enter vertebrates as antigens to produce immune reactions, thus obtaining antibodies that can specifically bind to pesticide molecules; Small molecular weight pesticides (molecular weight

2.8 Biosensors

Biosensor is an analytical device with selective and reversible response to specific chemical substances or bioactive substances, which consists of biosensor and electrochemical converter. It consists of identification elements, signal transmission and signal transmission circuits, and is characterized by integrating biochemistry, bioengineering, electrochemistry, material science and micro-manufacturing technology, and is a typical interdisciplinary product. According to its biological function, it can be divided into enzyme biosensor (including potential type and current type), immunosensor and microbial sensor [8]. It has the characteristics of miniaturization, fast response, less sample consumption, being inserted into biological tissues or cells, and realizing ultra-micro online fast tracking analysis, and has been widely used in pesticide residue analysis.

2.9 laboratory robots

Laboratory robot has been commercialized, but its application in pesticide residue analysis and environmental monitoring is still in its infancy, mainly due to the lack of flexibility in the change of robot working procedures and the lack of standardization in laboratory detection methods. In addition, the robot system moves slowly and usually needs a wide space. When the laboratory robot becomes more convenient and flexible, and the experimental methods are more standardized, its uses will be more and more.

3 Conclusion

Pesticide residue analysis is a comprehensive analytical science. The detection method should be simple, rapid and sensitive. According to the detection purpose, the nature of the pesticide to be detected and the type of the sample, the method that meets the requirements should be adopted. New analytical techniques will need the support of knowledge of cytochemistry, fermentation chemistry, immunochemistry and polypeptide arrangement structure. With the continuous development of science and technology, residue analysis technology is constantly updated, improved and developed rapidly.

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