p. P '- DDE detection

1. Scope of Application: This standard is applicable to the analysis of BHC and DDT in surface water, groundwater, and some sewage. This method uses petroleum ether to extract hexachlorocyclohexane and DDT from water, and after purification, they are determined using a gas chromatograph with an electron capture detector. When different instruments are used, the detection range of the method varies. γ- BHC is usually detected to 4 ng/L, while DDT can be detected to 200 ng/L. Organic compounds such as organophosphorus pesticides, unsaturated hydrocarbons, and phthalates in the sample also responded on the electron capture identification device, and these interfering substances can be removed with concentrated sulfuric acid. 2 Reagents and Materials 2.1 Carrier Gas Nitrogen: Purity 9.9%, oxygen content less than 5 ppm, purified using a 5A molecular sieve purification tube. 2.2 Reagents and materials used in the preparation of standard samples and sample pre-treatment. 2.2.1 Petroleum ether: Boiling range 30~60C or 60~90C, concentration 20 times, chromatographic determination without interference peak. If there is any interference, it needs to be re distilled using a full glass still. 2.2.2 Concentrated sulfuric acid (H: SO,): p=1.848/m1.2.2.3 Anhydrous sodium sulfate (Na; SO,): Bake in a 300C oven for 4 hours, cool to room temperature in a dryer, and place in a glass bottle for later use. 2.2.4 Sodium sulfate (Na; SO,. 10H; O): 208/L solution, extracted three times with petroleum ether before use, with a solution to petroleum ether ratio of 10:1. 2.2.5 Isooctane (C.K). 2.2.6 Benzene (C, H,): premium grade pure. 2.2.7 Chromatographic standard substance: a-Hexachlorocyclohexane γ- 666 β- Hexachlorocyclohexane, 8-hexachlorocyclohexane, P P '- DDE OP '- DDT, PP' - DDD PP '- DDT, with a purity of 95-99%. 2.2.8 Reserve solution: Weigh 100mg of each standard substance (2.2.7) to the nearest 1 mg, dissolve it in isooctane (2.2.5) (B-hexachlorocyclohexane, first dissolved in a small amount of benzene), and bring to volume in a volumetric flask to 100ml. Can be stored at 4 C for - years. 2.2.9 Intermediate solution: Use a pipette to measure eight reserve solutions, transfer them to a 100ml volumetric flask, and dilute with isooctane (2.2.5) to the mark. The volume ratio of eight reserve solutions is V. One big: V, - Rh: Vg big "Va k big tVpp '. DDE: Vop' - DDr: Vpp oDD * Vpp Dot=1+1: 3.5: 1 13.5:5: 318. 2.2 10 standard working solution for gas chromatography, based on the sensitivity and linearity requirements of the detector. Dilute the intermediate solution with petroleum ether (2.2.1) and prepare several concentrations of standard working solutions, which can be stored for 2 months at 4 C. 2.3 Reagents and materials used in the preparation of chromatographic columns 2.3.1. Reference for chromatographic columns and fillers 3 Relevant content of 6. 2.3.2 Solvent used for Xu Zai fixing solution: acetone

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