Modern agricultural pesticides are used in large quantities, with complex varieties and wide geographical distribution. The more developed the economy, the more pesticides are used. The use of pesticides can increase production and benefit it; the use of pesticides to contaminate soil, pollute drinking water, and pesticide residues in foods can harm public health and cause health risks. Trade-offs and trade-offs are the central issue of the current environmental impact of chemicals. Due to the high and frequent use of pesticides, pesticide residues may be present on crops, especially on their fruits. A recent survey conducted by the United States and the United Kingdom found that 73% of food crops did not detect pesticide residues, and vegetables and fruits were more severe. After the fruit is harvested, some need to be stored for a long time to be sold to the consumer. Therefore, it is inevitable to use a fungicide type preservative, and the outer skin and the pulp must have pesticide residues.
What is the residual organochlorine pesticide in our food? In 1992, China investigated the levels of organochlorine pesticide residues in basic dietary foods of people in Heilongjiang, Beijing, Sichuan, Zhejiang, and Guangdong provinces. Foods included the eight most closely related categories: food, vegetables, fruits, and poultry. , aquatic products, plants, eggs and milk. Although most of the residues of BHC and DDT did not exceed the Chinese Residue Limits, BHC could still be detected in 69% of the samples; DDT was detected in 42% of the samples. Although China stopped production and banned BHC and DDT in 1983, organochlorine pesticides are difficult to degrade and have a long life span, and dicofol is still used today for insecticides on crops such as fruit trees and cotton. Its metabolites in the environment. It is DDE, the latter structure is quite similar to DDT, and the toxicity is almost the same. Therefore, the current crop still has residues of organochlorine pesticides. This requires the determination of pesticide residues in crops. There are various methods for measuring the amount of pesticide residues, but gas chromatography has been widely used because of its high selectivity, high separation efficiency, high sensitivity, and fast analysis speed. According to (GB/T17332-1998), the 7800 gas chromatograph produced by Beijing Purui Analytical Instrument Co., Ltd. was used to analyze the residual amount of organochlorine pesticides in tea, and good results were obtained.
Second, the experimental part of the experimental instrument: GC7800 gas chromatograph (Beijing Purui Analysis Instrument Co., Ltd.)
Experimental conditions: Column: OV-1701 or SE-5430m×0.32mm×0.5um Dalian Zhonghuida Scientific Instrument Co., Ltd. Detector: Electron Capture Detector (ECD); Column Temperature: 200°C; Injector Temperature: 220 °C; Detector temperature: 220 ° C; carrier gas: high purity nitrogen, 8mL / min; tail gas: 16ML / min; injection volume: 1ul.
The manufacturing standard of the European standard plug (two rounds) is carried out according to the CE standard. European standard plugs are used in most European countries such as Germany, Austria, Holland, Sweden, Norway, Finland, and Russia. Since this standard is widely used throughout Europe, we call it the "Continental European" standard. The plug is two cylinders with a span of 19mm. The grounding level is completed by grounding the plugs on both sides. Central and Eastern Europe 7/7 European plugs have embedded pins, similar to French and Belgian sockets. The electrical parameter of the European standard socket is 10A-16A 230ACV AC power supply. The European standard socket is the safe socket in the world. The special grounding is mainly for the safety of people. Therefore, it is also the most widely used plug standard in the world. Note: The Italian standard plug has three cylinders and one wire, and the Danish and Swiss standard plugs have three cylinders into a triangle shape, and both have direct grounding pins.
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