Applications of the QuEChERS Method in the Residue Detection

Today, Hawach wants to talk about the pre-treatment process for pesticide residue detection from the perspective of food safety – QuEChERS, and also tell you how to pre-treat pesticide residue food.

QuEChERS Method in the Pretreatment for Pesticide Residue Detection

Introduction of the QuEChERS method

The present analytical methods and determining techniques, pre-treatment processes of samples, and the rapid and easy determination of pesticides remaining in food were hot spots in the field of international agricultural products and food safety. The food safety inspection and supervision institutions have specialized chemical laboratory staff sampling the ingredients on the market every day, to check whether pesticide residues are up to standard.

Principle of the QuEChERS method

Impurities can be removed and purified by means of the interaction between the adsorbent filler and the impurities in the matrix. The principle is similar to HPLC and SPE. Specifically, the sample to be tested is homogenized and acetonitrile extraction and salt extraction are stratified with the help of specific salts. The impurities are combined with adsorbents for centrifugal separation and purification finally.

Operating steps of the QuEChERS method

Pesticide residue detection in food is a process of quantitative analysis of the components in the complex matrix, including sample preparation, purification and enrichment, separation and detection, and comprehensive analysis. Pretreatment includes extraction and purification. Extraction is the process of dissolving and separating pesticide samples. Purification is an adsorption process of adsorbent and impurities to separate impurities and matrix.

Detection of Pesticide Residues in Tea

Status quo of QuEChERS method

Based on the significant advantages of the QuEChERS method and the continuous development of instrument detection technology, analysts continue to expand the application field of the QuEChERS method. At present, the QuEChERS method is widely used in the detection of pesticide residues in high moisture samples such as fruits and vegetables, but also in oils and fats, grains, soil, Chinese herbal medicines, detection of pesticide residues in samples of animal origin, food, and milk, eggs, the muscle tissue of drug residues in samples. In addition, its research and application areas include food additives, polycyclic aromatic shorts, biotoxin, drug residue detection, and identification of illegal additives in traditional Chinese medicine.

Application of the QuEChERS method

Due to the many advantages of the QuEChERS method, analysts have also conducted more research on its application in the detection of pesticide residues in tea, and have made some progress.

Used an improved QuEChERS method to analyze 86 pesticide residues in green tea, black tea, and dark tea. They have been extracted with triphenyl phosphate-added acetonitrile. The pH was adjusted with an agaric acid buffer solution. Anhydrous calcium chloride replaced anhydrous sulfuric acid. Magnesium removes excess water and is detected by LC-MS / MS and GC-MS / MS; the results show that the recovery rate of most pesticides among 86 pesticides is between 70% and 120%. When using the improved QuEChERS method to analyze the triazole fungicide residues in the tea leaves, acetonitrile was used as the extraction solvent. After purification by C18, PSA, and Flory silica, a liquid-liquid microextraction process was added to effectively reduce the interference of the matrix, the recovery rate of the obtained pesticide is between 91% -118%.
QuEChERS Kit Pouch Format

Optimization of the QuEChERS method

Compared with other plant-derived foods, tea is rich in alkaloids, tea polyphenols, and pigment compounds, which are easy to interfere with the detection. Therefore, optimizing the pretreatment conditions of tea samples is particularly important to reduce the detection limit and improve detection efficiency. When using the QuEChERS method for pretreatment, it is usually necessary to optimize the sampling volume, the types of extractants and purifiers and their amounts, etc., to meet the requirements of pesticide residue testing.

1. Optimization of sampling volume and sample pretreatment
The QuEChERS method was originally designed for vegetables and fruits with high water content, and the sampling volume is usually 10g. For tea leaves with low water content, the sampling volume should be appropriately reduced, usually 2g or 5g. Under the same conditions, reducing the particle size of the sample can increase its uniformity, making detection at a smaller sample size possible; however, if the sample particle is too small, it will affect the effect of centrifugal separation and supernatant absorption. Therefore, the appropriate particle size is particularly important for the feasibility and effectiveness of the detection.

Studies have found that the particle size of dried tea samples is 20-50 mesh is more appropriate; at the same time, in order to ensure that the analyte in the tea is easily extracted, a certain amount of water for soaking is often added. However, someone believes that for non-polar pesticides, the extraction of dry tea samples after soaking in water does not improve the extraction effect of such pesticides, but will increase the leaching of water-soluble impurities such as caffeine and increase subsequent purification difficulty.

It can be seen that whether water is added during the pretreatment of tea samples depends mainly on the polarity of the target pesticide. For the detection of polar pesticides, pretreatment with water immersion can be used to improve the recovery rate of pesticides. For non-polar pesticides, on the basis of ensuring a higher recovery rate, organic solvent extraction can be used directly to reduce the leaching of water-soluble impurities.

2. Selection of extractant
The choice of extractant is one of the key factors for the development of a multi-residue analysis method. The choice directly affects the level of pesticide recovery and the difficulty of subsequent purification. Common extraction solvents used in the QuEChERS method include acetonitrile, ethyl acetate, and acetone. Compared with ethyl acetate and acetone, when acetonitrile is used to extract pesticides in tea, there are fewer co-extracted substances. At the same time, sodium chloride is added. By salting out, acetonitrile and water are easily separated. Therefore, acetonitrile is the most commonly used extraction solvent for the analysis of pesticide residues in tea under the QuEChERS method.

However, under the action of acetonitrile, some pesticides (such as dicofol, etc.)

QuEChERS Method in the Veterinary Drug Residue Detection

After research, it has been found that the QuEChERS method has more prominent characteristics and can be applied in a variety of applications, including not only fruits and vegetables, but also milk, blood, and meat. In order to obtain more satisfactory test results, the researchers improved and innovated the QuEChERS method on the existing basis, so that the QuEChERS method can be applied to the detection of meat food, and pesticide residue on the meat food can be detected. If you want to purify meat food, you must remove its fat.

Therefore, relevant personnel should use a reasonable and scientific method to remove fat. In most cases, purifiers and extractants are used to purify meat food, so that the purity of the meat obtained and the accuracy of the test results are higher. This method has the advantages of simplicity, ease of operation, and low cost, so experts must actively use this method to create a safe and healthy food market for people, and apply this method to the detection of more high-fat foods, such as milk, various cooked foods, etc., which can accurately measure and analyze the pesticide residues of these foods to ensure food safety, and also promote the development of the agricultural market economy.

2m-15ml QuEChERS D-SPE Kit

Li Feng and others used the QuEChERS method combined with liquid phase tandem mass spectrometry to detect 12 kinds of sulfonamides, 19 kinds of quinolones, and 8 kinds of benzimidazole drugs and metabolites in chicken liver. Finally, good effects of protein denaturation precipitation centrifugation, matrix water removal, fat and carbohydrate removal, and degreasing are achieved. Wang Zhi et al. improved the QuEChERS method, using 0.5% acetic acid acetonitrile as the extraction solution, PRIME HLB solid phase extraction purification, nitrogen-blowing concentration, and reconstitution. Combined with UPLC-MS / MS high-throughput rapid detection of 8 kinds of hormones, 6 kinds of β-receptor agonists, and 4 kinds of antibiotic growth-promoting drugs in bovine liver. The results showed that the recovery rate was satisfactory and the relative deviation was small.

Conclusion of the QuEChERS method

The QuEChERS method has the advantages of convenience, economy, and high accuracy of the test results, so it is widely welcomed in food testing. The traditional food safety detection method has low technical content, insufficient accuracy of the detection results, and limited detection range. The QuEChERS method has a wide range of applications and can detect food, agricultural, and veterinary drug residues in a timely, efficient, and accurate manner.

With the continuous improvement of scientific and technological levels and the efficient research and development of new extractants and catalysts, the QuEChERS method will greatly play a role in the detection of food, agricultural, and veterinary drug residues.
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