Preparation Of Magnetic Pickering Emulsion And Its Extraction,Enrichment And Detection Of Trace Formaldehyde

Pickering emulsion is an emulsion system in which two or more incompatible fluids are formed by using solid particles as surfactants.Solid particles can be zero-dimensional nanospheres,two-dimensional nanorods and three-dimensional nanosheets.In addition,due to the special properties of particle emulsifiers themselves,such as catalysis,temperature sensitivity,p H sensitivity and magnetism,the particle emulsifiers also have different functions to form Pickering emulsions.For example,magnetic Pickering emulsion can be manipulated flexibly by using its magnetism through an external magnetic field.Besides,when the internal phase of Pickering emulsion is ionic liquid,the ionic liquid properties of Pickering emulsion can be used for many studies.In this paper,Fe₃O₄ nanoparticles with different morphology with good emulsifying ability were synthesized by solvothermal method.The emulsifiers were used to stabilize some water and oil systems.All of them could be effectively controlled by magnetic field.One of the magnetic ionic liquid Pickering emulsions was used to enrich the trace formaldehyde in water by emulsion microextraction technology to realize the trace formaldehyde detection by high performance liquid chromatography in water.The specific contents are as follows:1.Firstly,Fe₃O₄ nanoparticles with different morphology of superparamagnetic reverse spinel structure were prepared by solvothermal method.One is a 300 nm nanosphere and the other is a hexagonal nanosheet with a side length of about 20 nm.Nanosphere Fe₃O₄ can stabilize water-coated toluene system,water-coated[BMIM][PF₆]system and water-coated[EMIM][NTf₂]system to make toluene/water Pickering emulsion,[BMIM][PF₆]/water Pickering emulsion and[EMIM][NTf₂]/water Pickering emulsion.Nano-lamellar Fe₃O₄ can stabilize water-coated toluene system and water-coated[EMIM][NTf₂]system to make toluene/water Pickering emulsion,and[EMIM][NTf₂]/water Pickering emulsion.The surface charge and contact Angle of Fe₃O₄ also prove that these five Pickering emulsions can be formed.In addition,the above five emulsions can remain stable for three months at room temperature,which proves that these emulsions have good stability.Finally,under the action of external magnetic field,the magnetic Pickering emulsions have a good magnetic response,which indicated that the magnetic Pickering emulsions have the characteristics of flexible manipulation.2.The extraction effect of magnetically controlled Pickering emulsion drops on trace formaldehyde was investigated.Because formaldehyde has no absorption peak in UV,it is derived into formaldehyde 2,4-dinitrophenylhydrazine by 2,4-dinitrophenylhydrazine,and through the detection of formaldehyde 2,4-dinitrophenylhydrazine to achieve the detection of formaldehyde.Firstly,the derivation conditions were investigated,including microwave power,derivation time and p H of sample solution.Secondly,under the optimal conditions,the derivatives were extracted and enriched by magnetic Pickering emulsion.The ionic liquid phase was separated by magnetism,and then the formaldehyde content was extracted with organic solvent and detected by HPLC.The four concentrations of formaldehyde solution were 0.5μg/L,1μg/L,5μg/L,10μg/L,and the recoveries were 85.1%～93.8%.The derivatives remained stable for 2 h.Therefore,through the extraction and enrichment of trace formaldehyde,we can realize the rapid and effective detection of trace formaldehyde in water by high performance liquid chromatography.