Determination of sulfadimethoxine in milk with aptamer-functionalized Fe3 O4 /graphene oxide as magnetic solid phase extraction adsorbent prior to HPLC.

An aptamer (Apt) functionalized magnetic material was prepared by covalently link Apt to Fe3 O4 /graphene oxide (Fe3 O4 /GO) composite by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-hydroxysuccinimide, and then characterized by FTIR, X-ray diffraction and vibration sample magnetometer. The obtained composite of Fe3 O4 /GO/Apt was employed as magnetic solid-phase extraction adsorbent for the selective preconcentration of sulfadimethoxine (SDM) prior to the analysis by HPLC. Under the optimal conditions (sample pH of 4.0, sorbent dosage of 20 mg, extraction time of 3 h and methanol-5% acetic acid solution as eluent), a good linear relationship was obtained between the peak area and concentration of SDM in the range of 5.0 μg L-1 - 1500.0 μg L-1 with correlation coefficient of 0.9997. The limit of detection (S/N = 3) was 3.3 μg L-1 . The developed method was successfully applied to the analysis of SDM in milk with recoveries in the range of 75.9% - 92.3% and relative standard deviations less than 8.1%. The adsorption mechanism of Fe3 O4 /GO/Apt towards SDM was studied through the adsorption kinetics and adsorption isotherms, and the results show that the adsorption process fits well with the pseudo-second-order kinetic model and the adsorbate on Fe3 O4 /GO/Apt is multi-layer and heterogeneous. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.