A high efficient adsorbent for plant growth regulators based on ionic liquid and β-cyclodextrin functionalized magnetic graphene oxide

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(+)BenSO(3)(-), VOIm(+)NapSO(3)(-), VOIm(+)AQSO(3) and VOIm(+)NQSO(3), respectively. Then, ionic liquids and beta-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, beta-cyclodextrin, graphene oxide and Fe3O4@SiO2, including high surface area, high supramolecular recognition capability, super paramagnetism and large delocalized pi-electron system, which were successfully characterized. Among four kinds of ionic liquids functionalized adsorbents, the VOIm(+)AQSO(3) modified material exhibited high adsorption capability to 7 plant growth regulators compared with Fe3O4@SiO2/GO/beta-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/beta-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(+)AQSO(3)(-) and beta-cyclodextrin functionalized magnetic graphene oxide material (Fe3O4@SiO2/GO/beta-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 mu g/kg and 0.03-0.58 mu g/kg, respectively. The satisfactory linearities were acquired in the concentration of 2-50 mu g/kg with the correlation coefficients higher than 0.9982. Taken together, the synthesized Fe3O4@SiO2/GO/beta-CD/IL was a highly effective magnetic solid phase extraction adsorbent for the enrichment of trace level of plant growth regulators in vegetable samples.