Endogenous substances,such as organic acids in food,can interfere with the detection of trace residues.To eliminate this effect,the magnetic adsorbent material was obtained by directly modifying acidified Fe3O4 with N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane(KH792)as an amination reagent.The optimal modification condi-tion of KH792 for acidified Fe3O4 was optimized by response surface methodology,which was 82.5℃,pH=4.9,and KH792 addition of 1.8 mL.Under these optimal conditions,the acidified Fe3O4 directly modified by KH792 has an adsorption capacity of 22.8 mg/g and shows a 188%increase in the adsorption capacity of the gallic acid compared to commercially available Fe3O4.Additionally,the modified Fe3O4 exhibits excellent performances of rapid solid-liquid separation,good stability,and dispersibility.The properties of the directly modified products were charac-terized by BET,Zeta potential,FTIR,and XPS.The results show that KH792 bonds on Fe3O4 surface hydroxyl group's by Fe-O-Si bonding,and acidification improves the number of hydroxyl groups on Fe3O4 surface,thus improv-ing the KH792 modification for Fe3O4.The magnetic products prepared in this work can be used for the purification of organic acids in complex sample matrices.
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