Four types of ionic liquids which composed of cation with imidazole ring and anion with benzene, naphthalene, anthraquinone and naphthoquinone ring were prepared and named VOIm+BenSO3-, VOIm+NapSO3-, VOIm+AQSO3- and VOIm+NQSO3-, respectively. Then, ionic liquids and β-cyclodextrin functionalized magnetic graphene oxide materials were firstly synthesized for the extraction of 23 plant growth regulators in vegetable samples. The synthesized materials anticipated the unique properties of ionic liquids, β-cyclodextrin, graphene oxide and Fe3O4@SiO2, including high surface area, high supramolecular recognition capability, superparamagnetism and large delocalized π-electron system, which were successfully characterized. Among four kinds of ionic liquids functionalized adsorbents, the VOIm+AQSO3- modified material exhibited high adsorption capability to 7 plant growth regulators compared with Fe3O4@SiO2/GO/β-CD, Fe3O4@SiO2/GO and other three types of ionic liquids based adsorbents. Parameters that could affect the recoveries of 7 plant growth regulators were investigated, such as mass ratio of Fe3O4@SiO2/GO/β-CD to ionic liquids, salt concentration, pH, amount of adsorbent, extraction time and desorption solvent. Under the optimal condition, the magnetic solid phase extraction method using VOIm+AQSO3- and β-cyclodextrin functionalized magnetic graphene oxide material (Fe3O4@SiO2/GO/β-CD/IL) as adsorbent was developed and coupled with ultra-high performance liquid chromatography-triple quadrupole linear ion trap mass spectrometry for the determination of 7 plant growth regulators in vegetable samples. Validation results showed that the limit of detection and limit of quantitation were in the range of 0.01-0.18 μg/kg and 0.03-0.58 μg/kg, respectively. The satisfactory linearities were acquired in the concentration of 2-50 μg/kg with the correlation coefficients higher than 0.9982. Taken together, the synthesized Fe3O4@SiO2/GO/β-CD/IL was a highly effective magnetic solid phase extraction adsorbent for the enrichment of trace level of plant growth regulators in vegetable samples.
Keywords: Graphene oxide; Ionic liquid; Magnetic solid phase extraction; Plant growth regulators; β-cyclodextrin.
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