▎ 摘　　要

NOVELTY - Preparation of composite magnetic nanoparticles involves mixing a mixture of graphite powder and potassium permanganate, with concentrated sulfuric acid and phosphoric acid, stirring, cooling, adding hydrogen peroxide, stirring, reacting, centrifuging, separating precipitate (A), mixing precipitate (A) and hydrochloric acid, centrifuging, separating precipitate (B), washing precipitate (B) with water, freeze-drying precipitate (B) having a pH of 6-8, obtaining graphene oxide, mixing graphene oxide and distilled water, ultrasonically dispersing, adding dopamine hydrochloride, stirring, adding 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, stirring, freeze-drying, obtaining dopamine-modified graphene oxide, ultrasonically dispersing obtained dopamine-modified graphene oxide in water, dissolving, adding iron(II, III) oxide and anhydrous toluene, reacting, separating the solid from the solution, washing, and drying washed solid. USE - Preparation of composite magnetic nanoparticles used for pretreatment of vegetable oil e.g. tea oil, linseed oil, and rice bran oil (all claimed). ADVANTAGE - The method enables simple preparation of composite magnetic nanoparticles. The composite magnetic nanoparticles enable rapid and stable detection of benzopyrene in vegetable oil with excellent sensitivity and repeatability. DETAILED DESCRIPTION - Preparation of composite magnetic nanoparticles involves mixing a mixture of graphite powder and potassium permanganate, with 98 wt.% concentrated sulfuric acid and more than 85 wt.% phosphoric acid, stirring at 40-06 degrees C for 40-50 hours, cooling to 32-37 degrees C, adding 30 wt.% hydrogen peroxide until no foam is formed, stirring, reacting at 32-37 degrees C for 3-5 hours, centrifuging, separating precipitate (A), mixing precipitate (A) and 25 wt.% hydrochloric acid, centrifuging, separating precipitate (B), washing precipitate (B) with water, freeze-drying precipitate (B) having a pH of 6-8, obtaining graphene oxide, mixing graphene oxide and distilled water, ultrasonically dispersing, adding dopamine hydrochloride, stirring at room temperature for 1-1.5 hours, adding 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, stirring at 62-67 degrees C for 20-30 hours, freeze-drying, obtaining dopamine-modified graphene oxide, ultrasonically dispersing obtained dopamine-modified graphene oxide in water, dissolving, adding iron(II, III) oxide and anhydrous toluene, heating, stirring at 50-100 degrees C for 3-7 hours, separating the solid from the solution, washing the solid with absolute ethanol and distilled water until the supernatant is colorless, and drying washed solid. The weight ratio of dopamine-modified graphene oxide and iron(II, III) oxide is 4:15. The volume ratio of water and anhydrous toluene is 1:2. The weight-volume (g/L) ratio of dopamine-modified graphene oxide and anhydrous toluene is 8:1. The weight ratio of graphite powder and potassium permanganate is 1:6. The volume ratio of concentrated sulfuric acid and phosphoric acid is 9:1. The weight-volume (g/L) ratio of the graphite powder and concentrated sulfuric acid is 1:120. The weight-volume ratio (g/L) of graphene oxide and distilled water is 1:250. An INDEPENDENT CLAIM is included for pretreatment of benzopyrene-containing vegetable oil using magnetic nanoparticles, which involves mixing vegetable oil, 1 mol/L tetra-n-butylammonium bromide, ethanol and 1 mol/L potassium hydroxide, stirring, heating at 70-90 degrees C for 4-15 minutes, performing phase transfer catalytic saponification, adjusting pH of the saponified liquid to 3-7 at 20-30 degrees C, adding magnetic nanoparticles, stirring for 0.5-10 minutes, reacting, separating magnetic nanoparticles from the saponification liquid, adding methanol, mixing, reacting, filtering using nylon filter material having an aperture size of 0.22 mu m, and obtaining a benzopyrene-containing test solution. The volume ratio of tetra-n-butylammonium bromide, absolute ethanol and potassium hydroxide is 1:10:40. The weight-volume ratio of vegetable oil and tetra-n-butylammonium bromide is 5:4.