▎ 摘　　要

NOVELTY - A magnetic nanocomposite material is prepared by using graphene oxide, ferric chloride hexahydrate, preparing magnetic graphene oxide from ferrous chloride tetrahydrate in alkaline solution, forming silica modified magnetic graphene oxide with magnetic solid phase extraction adsorbent in ethyl silicate in anhydrous ethanol and preparing magnetic solid phase extraction adsorbent polypyrroloaniline modified silica-coated magnetic graphene oxide from pyrrole, aniline, ferric chloride solid and silica-modified magnetic graphene oxide in dichloromethane. USE - Magnetic nanocomposite material used for detecting heavy metals ion e.g. chromium ion and lead ion in food e.g. rice or milk (all claimed). ADVANTAGE - The magnetic nanocomposite material has excellent adsorption performance and provides efficient and sensitive metal detection method. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: (1) preparation of magnetic nanocomposite material which involves dispersing graphene oxide in water under nitrogen protection, stirring vigorously, increasing temperature to 70-90 degrees C, dissolving ferric chloride hexahydrate, ferrous chloride tetrahydrate in water to make solution, adding the prepared solution at 70-90 degrees C, adjusting pH to 10-12 by adding ammonia solution, mechanically stirring at 70-90 degrees C for 1-2 hours to obtain magnetic graphene oxide, dispersing ethyl silicate in water, stirring, ultrasonically processing to make a suspension, adding magnetic graphene oxide to ethanol, adding ethyl silicate suspension under ice bath at 0-4 degrees C, vigorously stirring for 10-20 minutes, adding ammonia solution to the system with stirring in drops, adjusting pH to 9-11, continuing stirring in an ice bath at 0-4 degrees C for 8-12 hours to obtain silica-modified magnetic graphene oxide, dispersing magnetic graphene oxide/silicon dioxide in dichloromethane, ultrasonically processing, adding pyrrole and aniline, placing the prepared mixture in an ice bath at 0-5 degrees C, adding ferric chloride solid, initiating polymerization under mechanical agitation, stirring at 0-5 degrees C for 5-8 hours, adding anhydrous ethanol, reacting for 7-12 hours at room temperature, separating the prepared nanocomposite repeatedly, washing with distilled water and ethanol and drying magnetic graphene oxide/silicon dioxide-doped-polypyrrole polyaniline nanocomposite for 6-8 hours; (2) use of magnetic nanocomposite material or detecting heavy metals in food; and (3) detection of heavy metals which involves pretreating food samples in a microwave digestion tank to prepare sample solution, extracting magnetic solid phase, concentrating by adding magnetic nanocomposite material to the food sample, ultrasonically processing, mixing, separating, discarding supernatant to obtain residue, adding nitric acid solution to the residue, mixing, separating to prepare supernatant, carrying out heavy metal ion elution by adding 4-10 mL nitric acid solution to the residue, mixing, separating to form supernatant and determining two trace heavy metal ion operating conditions in food by inductively coupled plasma mass spectrometry as given in the specification.