Organochlorine pesticides are a kind of high-efficiency broad-spectrum pesticides, which are widely used to kill agricultural pests. They were once the most widely used pesticides in various countries. Due to its high residues and high toxicity, China has formulated residue limit standards for foods such as grains, fruits and vegetables, and there are very few standards for pesticide residues in traditional Chinese medicinal materials. This article analyzes and studies the residues of organochlorine pesticides in astragalus and licorice, and calls on relevant parties to pay attention to the problem of pesticides contaminating Chinese medicinal materials and ensure the quality of Chinese medicinal materials. The sample was extracted with acetone. In the presence of sodium chloride, the liquid-liquid distribution was carried out with dichloromethane. The extract was purified with concentrated sulfuric acid. The SE-54 elastic quartz capillary column was used. GC / ECD was used to detect organic chlorine Structure, heptachlor, aldrin) pesticide residues, the minimum detection concentration is 3.2 × 10-2 ～ 1.4ng / g, and the sample recovery rate is 77.8% ～ 102.5%. Determination of residue. 1. Instruments American Varian6000 gas chromatograph (63Ni electron capture detector); Varian4270 recorder. American Dima SE-54 elastic quartz capillary column (30m × 0.32mm × 0.25μm). Ultrasonic cleaner (Germany) type T-310; vacuum rotary concentrator (Japan) type NE-1; KD concentrator; other necessary laboratory equipment and utensils. 2. Reagents Pesticide standard products: The purity of the six six six (BHC) isomers (α-BHC, β-BHC, γ-BHC, δ-BHC) were 99.0%, 99.2%, 99.0%, 98.9%, and heptachlor The purity is 99.1%, the purity of Aldrin is 99.0%, and the purity of DDT isomers (pp′-DDE, pp′-DDD, op′-DDT, pp′-DDT) is 98.0%, 98.5%, 98.0%, 98.2% (provided by Qinhuangdao Commodity Inspection Bureau). Acetone, methylene chloride, sodium chloride, anhydrous sodium sulfate and concentrated sulfuric acid are all analytically pure; n-hexane (analytically re-distilled); double-distilled water. 3. Experimental steps 3.1 Extraction and purification Weigh accurately 2g of the crushed sample powder, add 100mL of acetone and 20mL of water to a 100mL Erlenmeyer flask with a stopper, ultrasonically extract for 60min, then add about 6g of sodium chloride and 30mL of methylene chloride, and sonicate for 30min Let it stand to completely separate the water phase and the organic phase. The organic phase was transferred into a 100mL Erlenmeyer flask with a certain amount of anhydrous sodium sulfate, dehydrated, 35mL of the dried organic phase was placed in a 100mL rotary evaporating flask, concentrated under reduced pressure in a 40 ° C water bath to about 0.5mL, and the concentrate Transfer to a 10mL stoppered test tube, wash the evaporating flask with 5mL of n-hexane in fractions, and combine the washing solution in the test tube. Carefully add approximately 1 mL of concentrated sulfuric acid to the test tube, shake for 1 min, and centrifuge (3000 r / min) for 10 min. The supernatant was transferred to a KD bottle, the test tube was washed twice with n-hexane, the washing liquid was combined, the solution was concentrated to 1.0 mL, and 1.0 μL was taken for GC analysis. 3.2 Measurement conditions Carrier gas: high-purity nitrogen; pre-column pressure: 0.6 kg / cm2; supplementary gas flow rate: 22 mL / min; inlet temperature: 180 ° C; detector temperature: 290 ° C; shunt time: from 0.10 min to 1.60min stop, 1.5min in total; split ratio: 15: 1; column heating program: initial 140 ℃, 10 ℃ / min to 210 ℃, 8 ℃ / min to 250 ℃, hold for 4min. Paper speed: 0.5cm / min; attenuation: 8; quantification by external standard method. 3.3 Standard curve drawing Pesticide standard stock solution (all using n-hexane as solvent): α-BHC: 80 μg / mL, β-BHC: 460 μg / mL, γ-BHC: 275 μg / mL, δ-BHC: 680 μg / mL, heptachlor: 280 μg / mL, Aldrin: 378 μg / mL, pp′-DDE: 490 μg / mL, pp′-DDD: 121 μg / mL, op′-DDT: 330 μg / mL, pp′-DDT: 270 μg / mL. Pipette a certain amount of standard stock solution and dilute to 5.0mL with n-hexane, so that the concentration of each standard in the mixed pesticide standard solution is: α-BHC: 8 × 10-2μg / mL, β-BHC: 11.96μg / mL, γ-BHC: 1.10 μg / mL, δ-BHC: 0.952 μg / mL, heptachlor: 1.40 μg / mL, Aldrin: 2.27 μg / mL, pp′-DDE: 0.980 μg / mL, pp′-DDD: 2.42 μg / mL, op′-DDT: 2.64 μg / mL, pp′-DDT: 0.270 μg / mL. Pipette a certain volume of the above mixed standard solution into a 5.0mL volumetric flask, make a series of dilutions with n-hexane, and take 1.0μL of injection to obtain a standard curve, see Table 1. 4. Results and discussion 4.1 Extraction and purification In the analysis of organochlorine residues in Chinese herbal medicines and other plant samples, the capillary columns commonly used are mostly non-polar or weakly polar, with a length of 25-30m and a medium diameter of 0.25-0.32mm. In this experiment, SE-54 elastic quartz is used On the capillary column, under the above experimental conditions, 10 kinds of organic chlorine were separated well, and the separation time was within 16min. Dilute the pesticide standard solution to different concentrations for measurement, use 5 times the noise as the minimum detection amount of the method, and sample the 2g sample to calculate the minimum detection concentration. The extraction method used in this experiment mainly refers to the on-line extraction method proposed by H. Steiwandter. The main principle is to use the role of electrolyte, according to the principle of salting out, so that pesticides from the aqueous phase into the organic phase. In this experiment, acetone was used as the extractant. At the same time, solid sodium chloride was added to the acetone extract to separate the pesticides. At the same time, dichloromethane was added to perform liquid-liquid distribution. The advantage of this method is that there is no need to extract and filter the sample multiple times, and liquid-liquid distribution does not need to be transferred to a separating funnel. After the water in the sample extract is dried over anhydrous sodium sulfate, it will not affect the measurement results, and it can reduce the loss of pesticides. The purification of organochlorine pesticides mostly adopts sulfonation method. The sulfonation method used in this experiment removes the operation of the separating funnel, and directly adds concentrated sulfuric acid to the extraction concentrate, which reduces the experimental operation steps and improves the safety and accuracy of the experiment. The sample extract only needs to be sulfonated once with concentrated sulfuric acid to achieve the purpose of purification. 4.2 Sample recovery experiment In the samples of astragalus and licorice, a certain amount of mixed standard solution was added to carry out the sample recovery experiment. The samples were carried out according to the above extraction, purification, and determination operation procedures. 4.3 Determination of actual samples Accurately weigh medicinal materials (powder) from different origins. (Xie Yinan / Editor) Mini portable computer writing tablet, both a Calculator and a writing pad, nano-scale elastic fit buttons, comfortable silicone button feel, increased surface area, beautiful design, silicone buttons increase wear resistance, improve service life, quiet learning, comfortable learning without Interference, suitable products for school and class, the screen does not emit light and does not hurt the eyes. 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