| Plant growth regulators?PGRs?are widely used in agriculture because of their regulation function in the plant growth.Nevertheless,the overuse of PGRs might lead to malformed organ,hollow fruit and mummy,premature senescence of leaves and even death for plants.Meanwhile,the excessive residues of PGRs in fruits and vegetables also maybe a potential threat to humans and animals associated with precocity,carcinogenicity,impaired reproduction,neurotoxicity and acute toxicity.On account of the low concentration of PGRs and complexity of the plant matrix with plenty of primary and secondary metabolites,it is urgency to develop a rapid,simple and selective pretreatment method prior to instrumental analysis.Therefore,based on the developed separation and analysis method with high sensitivity and accuracy,the PGRs exposure would be monitored well.Magnetic solid phase extraction?MSPE?is a pre-treatment technique that use magnetic materials as adsorbents.In MSPE,the adsorbents composed of magnetic inorganic materials and non-magnetic materials were directly dispersed in sample solution for extraction of the target analytes,and then were rapidly separated by an external magnetic field.Thus,compared with traditional SPE,MSPE has the merits of high adsorption efficiency,easy operation,fast separation,time and labor saving.As the non-magnetic materials in adsorbent could improve the dispersibility and the adsorption efficiency of adsorbents,great attentions have been focused on synthesis of new nano-magnetic adsorbents and exploring their potential application in MSPE.Graphene oxide?GO?is an oxidized form of graphene?G?,which contains many active functional groups such as carboxyl?-COOH?,hydroxyl?-OH?and epoxy groups?-C-O-C-?in its chemical structure.For application in the field of adsorption,the surface of GO was usually modified by other materials.?-cyclodextrin??-CD?is a torus-shaped cyclic oligosaccharide composed of seven D-glucose units,which possesses hydrophobic cavity and hydrophilic wall.The hydrophobic inner cavity has remarkable capacity to selectively form host-gust inclusion complex with various molecules of a certain size and polarity.In addition,?-CD is an environmentally friendly and water-soluble molecule,which can improve the solubility and biocompatibility of functional materials.Moreover,the?-CD functional material could be used as adsorbents for selective separation and extraction analytes with particular chemical structures.In this work,a?-CD functionalized magnetic graphene oxide?Fe3O4@SiO2/GO/?-CD?was prepared and used as adsorbent in MSPE technique for simultaneous determination of multiple PGRs.Part? Fabrication and characterization of?-cyclodextrin functionalized magnetic graphene oxideObjective:A?-cyclodextrin functionalized magnetic graphene oxide material?Fe3O4@SiO2/GO/?-CD?was synthesized and character-ized.Methods:Fe3O4@SiO2 was prepared by chemical coprecipitation method and silica coating technology.Fe3O4@SiO2/GO was synthesized by chemical bonding method.?-CD was directly functionalized on surface of Fe3O4@SiO2/GO.The synthesized materials were character-ized by scanning electron microscope?SEM?,transmission electron microscope?TEM?,Fourier transform infrared spectroscopy?FT-IR?,vibrating sample magnetometry?VSM?and X-ray photo-electron spectroscopy?XPS?,thermogravimetric analyzer?TGA?,CHNS/O elemental analyzer and BET analysis.Results:The SEM and TEM images showed that the surface of Fe3O4@SiO2/GO presented some wrinkles and flake structures.Fe3O4@SiO2/GO/?-CD showed a more rougher surface than synthesized intermediate products.The results of BET analysis suggested that micropores and mesopores coexisted in the Fe3O4@SiO2/GO/?-CD nanoparticles.The wide scan XPS spectra of Fe3O4@SiO2/GO/?-CD exhibited that the material was mainly composed of Si,C,N,O and Fe.In FT-IR spectra,the characteristic peaks for Fe-O-Fe,Si-O-Si and C=O were observed at 577 cm-1,1080 cm-1 and1717 cm-1,respectively.The results of elemental analysis revealed that the content of oxygen in Fe3O4@SiO2/GO/?-CD was greater than that in Fe3O4@SiO2/GO.The content of?-CD in synthesized Fe3O4@SiO2/GO/?-CD was calculated to be 9.33t%?wt?by TGA analysis.The results of VSM showed that the synthesized materials were superparamagnetic.Conclusion:The Fe3O4@SiO2/GO/?-CD nanoparticles were successfully prepared in this work.Part? Determination of 5 plant growth regulators in vegetables by magnetic solid phase extraction coupled with gas chromatography-mass spectrometryObjective:A magnetic solid phase extraction technique?MSPE?using Fe3O4@SiO2/GO/?-CD as adsorbent was developed and coupled with gas chromatography-mass spectrometry for determination of 5 PGRs in vegetables.Methods:The vegetable samples were extracted by 1%acetic acid in acetonitrile.Then,the MSPE technique using Fe3O4@SiO2/GO/?-CD was developed by optimizing adsorbent amount,extraction time,desorption condition and so on.GC-MS with external standard method was used for quantitation.Results:Under the optimal condition,good linear relationships for 5 PGRs were observed in the range of 1?g/kg100?g/kg with determination coefficients?R2?from0.9983 to 0.9996.The limit of detection of 5 PGRs were from 0.04?g/kg to 0.28?g/kg.The recoveries of 5 PGRs in spiked vegetable samples were in the range of 75.8%109.6%.The intra-day and inter-day relative standard deviations were in the range of 0.8%7.6%and 1.8%6.2%,respectively.Conclusion:The synthesized Fe3O4@SiO2/GO/?-CD could selectively adsorb 5 PGRs.The proposed MSPE-GC-MS method based on Fe3O4@SiO2/GO/?-CD as adsorbent for analysis of 5 PGRs was quick,accurate,sensitive and selective.Part? Determination of 9 plant growth regulators in vegetables by magnetic solid phase extraction coupled with ultra-high performance liquid chromatography-triple quadrupole linear ion trap mass spectrometryObjective:Development of an analytical method for 9 PGRs which combined the MSPE technique utilizing Fe3O4@SiO2/GO/?-CD as adsorbent with ultra-high performance liquid chromatography-triple quadrupole linear ion trap mass spectrometry?MSPE-UHPLC-MS/MS?.Methods:The vegetables were extracted by 1%acetic acid in acetonitrile.Based on Fe3O4@Si O2/GO/?-CD as adsorbent,the MSPE method for 9PGRs were established by optimizing the parameters such as pH of extraction solvent,amount of adsorbent,extraction time and so on.Then quantitation was achieved by UHPLC-MS/MS with external standard method.Results:Under the optimized condition,the studied 9 PGRs exhibited good linearity in the range of 2?g/kg50?g/kg with coefficient of determination?R2?ranging from 0.9975 to 0.9999.The limits of detection were in the range of 0.04?g/kg0.29?g/kg.The spiked recoveries were in the range of 77.7%108.3%.The intra-day and inter-day relative standard deviations were in the range of 1.7%8.4%and 2.8%10.8%,respectively.Conclusion:The developed MSPE-UHPLC-MS/MS method which based on Fe3O4@SiO2/GO/?-CD as adsorbent could simultaneously detect 9 PGRs. |
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