▎ 摘　　要

NOVELTY - A magnetic adsorbent preparing method involves dissolving graphene oxide in 50 ml N,N-dimethylformamide ultrasonically. 0.1 g N-hydroxysuccinimide and 0.2 g 1-ethyl-3-(3-dimethylaminopropyl)carbo-di-imide is added to the obtained mixture and stirred at 25 degrees C for 2 hours. Iron oxide-silica with amine groups is added to the obtained mixture and stirred at 25 degrees C overnight. The obtained mixture is separated and dispersed in isolated external magnetic field. The obtained mixture is washed for 2-3 times, and dried to obtain finished product. USE - Method for preparing magnetic adsorbent that is utilized in detecting 16 kinds of preservatives in vegetables (claimed), where the preservatives are methyl paraben, ethyl paraben, propyl paraben, butyl paraben, diphenyl ether, ethyl naphthalene, p-phenylphenol, pyrimethanil, chlorpyrifos, triadimefon, procymidone, imazalil, myclobutanil, flusilazole, propiconazole and prochloraz. ADVANTAGE - The method enables preparing magnetic adsorbent with short diffusion distance, small amount, shorter equilibration time, high extraction capacity and extraction efficiency, and better recovery rate and precision, and detecting 16 kinds of preservatives simultaneously. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a method for detecting 16 kinds of preservatives in vegetables, which involves weighing 10 g mixed vegetable slurry in 50 ml centrifugal tube, adding 20 ml acetonitrile and 4 ml ammonium acetate with concentration of 2 mol/l to the mixture, stirring the mixture for 2 minutes, oscillating the mixture for 10 minutes, adding 5 g sodium chloride to the centrifugal tube, blending the mixture uniformly for 1 minute in vortex, centrifuging the mixture at 5000 revolutions/minute for 3 minutes, absorbing supernatant (S1) in centrifugal tube, purifying sample with 100 mg iron oxide-silica and graphene, and 500 mg anhydrous magnesium sulfate, adding the supernatant (S1) to the centrifugal tube, blending the mixture for 3 minutes, separating the mixture under magnetic field, absorbing supernatant (S2) in rotary evaporation tank, placing the rotary evaporation tank in water bath at 40 degrees C for concentration, drying concentrate, adding 1 ml acetone to the concentrate, dissolving the concentrate, filtering the mixture with filter membrane, and detecting 16 kinds of preservatives in sample with gas chromatography-mass spectrometry (GC-MS) method, where the GC-MS conditions comprise DB-5MS quartz blood capillary column, initial column temperature of 70 degrees C, flow rate of 1.2 ml/minute, electron ionization source, ion source temperature of 230 degrees C, quadrupole temperature of 150 degrees C, interface temperature of 280 degrees C, injection volume of 1 mu l, inlet temperature of 250 degrees C and total running time of 28 minutes.