Preparation of magnetic metal-organic framework MIL-101(Fe) and its application in the extraction of anthraquinones in rhubarb

In this work, a magnetic octahedral metal-organic framework (Fe3O4@NH2-MIL-101(Fe)) was synthesized for the magnetic solid-phase extraction of three anthraquinones, including aloe-emodin, emodin, and physcion, in rhubarb. The Fe3O4@NH2-MIL-101(Fe) exhibits a high specific surface area of 259.2 m(2)/g with an average pore size of 6.0 nm and high magnetic responsivity of 23.4 emu/g, which may be used as an adsorbent for rapid preconcentration and separation of target analytes. The main parameters for magnetic solid-phase extraction of anthraquinones, including the amount of adsorbent, extraction time, extraction temperature, extraction pH, elution solvent, and elution time, were systematically optimized. The whole extraction process requires a very low amount of adsorbent and a small volume of the sample. Besides, under the optimized conditions, the method shows satisfactory spiked recovery for anthraquinones in the range of 93.3%-109.1% and the limits of detection are 1.7-3.4 ng/mL. The relative standard deviations for intra- and inter-day precision are 0.2%-1.3% and 0.2%-0.6%, respectively. The experimental results indicate that the developed method is feasible for the analysis of anthraquinones in rhubarb.