Preparation Of Polymer Monolithic Fiber Incorporated With Graphene Oxide And Its Application On The Analysis Of Organophosphate Esters In Soil

Due to the complexity of soil samples matrix and low concentration level of analytes,it is essential to pretreat the analytes from soil samples before the instrument analysis.Organophosphate esters(OPEs)have attracted increasing concern,due to its large consumption,wide distribution in environment and significant toxicological effects.The pretreatments of OPEs in soil are mainly categorized into such two steps as organic solvent extraction and column purification,which are cumbersome,time-consuming,consuming a large amount of organic solvents.Solid phase micro-extraction(SPME)is a kind of solvent-free and eco-friendly extraction technique,which integrates sampling,enrichment,matrix removal and sample injection into one step,and the sample can be extracted directly without pretreatment.Based on the above advantages of SPME,it can be applied in the analysis of OPEs in soil.Since there exist problems that coating fiber of SPME owns a small capacity of extraction and it is prone to detach,very little research has addressed the analytical methods of OPEs in the soil.Thus we prepared non-coating monolithic fiber,which aims to overcome the insufficiency of the coating fiber and enrich the research of the analytical method of OPEs.In this study,graphene oxide(GO)incorporated polymer monolithic fiber(MF)was synthesized in fused silica capillary,and was used as SPME fiber.The method of headspace solid phase microextraction(HS-SPME)based on poly(AM-EGDMA-GO)monolithic fiber,coupled with GC-FPD,was applied for the extraction and analysis of OPEs in environmental soil.The detailed research contents are listed as follows:1.The preparation and characterization of graphene oxide incorporated polymer monolithic fiber:Adding an appropriate amount of GO into the prepolymerized mixture,poly(AM-EGDMA-GO)monolithic fiber was synthesized through in situ polymerization by thermal irradiation in fused silica capillary.The poly(AM-EGDMA-GO)monolithic fiber,poly(AM-EGDMA)monolithic fiber,and reduced graphene oxide were characterized by Fourier transform infrared spectroscopy(FT-IR),Raman spectroscopy(Raman),scanning electron microscopy(SEM),thermo gravimetric analysis(TGA)and N2 adsorption-desorption isotherm.The results show that GO incorporated poly(AM-EGDMA-GO)monolithic fiber and two other fibers were successfully prepared.Moreover,three fiber materials all possessed porous structure,large specific surface area and good thermal stability.2.The study on the application of GO incorporated polymer monolithic fiber in the detection of OPEs in environmental soil:The prepared fiber was used as the extraction material and combined with GC-FPD to optimize the HS-SPME extraction conditions such as extraction time,extraction temperature,added water volume,salt concentration,stirring rate and desorption time.GO incorporated poly(AM-EGDMA-GO)monolithic fiber,compared with poly(AM-EGDMA)monolithic fiber,RGO fiber and commercial coated fiber(PDMA,PA)in extraction efficiency,showed the best extraction efficiency under the optimized conditions.Adsorption kinetics and adsorption isotherm were adopted to study the adsorption mechanism of the poly(AM-EGDMA-GO)monolithic fiber towards target molecule.The result demonstrated that adsorption accorded with the pseudo-first-order model and the adsorption isotherm conformed to the Langmuir isotherm model,which can be utilized to better describe the adsorption equilibrium of poly(AM-EGDMA-GO)monolithic fiber for OPEs.Under the optimum conditions,a sensitive method based on GO incorporated polymer monolithic fiber HS-SPME coupled with GC-FPD was established and applied in the analysis of OPEs in real soil samples.The result indicated that target analytes had a good linear relationship in the concentration range of 0.05-100 ng g-1(R2>0.99),and the limit of detection(LOD),based on a signal-to-noise ratio(S/N)of 3,were in the range from 0.0092 to 0.072 ng g-1.The poly(AM-EGDMA-GO)monolithic fiber was employed for the determination of OPEs in five real soil samples with good added recoveries from 80.1%to 105.6%.This method has satisfactory accuracy and precision,which could be applied to the detection and analysis of OPEs in environmental soil.