Study On The Porous Polymers-based In-tube Solid Phase Microextraction On-line Coupled With Chromatography Techniques And The Applications In The Monitoring Of Pollutants

In-tube solid phase microextraction(IT-SPME)is one of well accepted sample pretreatment techniques,which integrates sample injection,purification,and enrichment into one procedure,and is easy to realize automatic pretreatment and online combination with chromatographic separation system.However,it still suffers from low extraction capacity and low extraction efficiency in applications.To solve the above dilemma,the present study utilized the merits of porous monolithic materials and magnetic microfluidic principles to enhance extraction performance of IT-SPME.The prepared new microextraction columns were coupled with high performance liquid chromatography(HPLC)system to develop on-line IT-SPME-HPLC analytical technique and apply to quantify various organic pollutants and different forms of Cr in complex samples.The main contents are as follows:(1)According to the molecular structures and chemical properties of polycyclic aromatic hydrocarbons(PAHs),a new poly(9-vinylanthracene-co-ethylene dimethacrylate)monolith-based capillary microextraction column was in-situ prepared and was employed as the adsorbent of IT-SPME for PAHs extraction.The extraction parameters,including sample volume,adsorption flow rate,composition and volume of the desorption solution,desorption flow rate,sample pH and ion strength,were thoroughly investigated.An on-line method of IT-SPME adopting two six-way valves and coupled with HPLC-fluorescence detection was developed.The limits of detection(LODs,S/N=3)for PAHs in water and milk samples were in the ranges of 0.017-0.29 ng/L and 0.10-2.36 ng/L,respectively.In addition,satisfactory precision and fortified recoveries were obtained.In comparison with the reported analytical methods of PAHs,the present approach exhibited some merits such as high sensitivity,environmental friendliness and being easy to realize on-line analysis.(2)To improve the extraction capacity of IT-SPME,a capillary microextraction column based on metal organic frameworks(MOFs)was synthesized by two steps.Firstly,4-vinylbenzoic acid was using as monomer to form porous monolithic material in a quartz capillary.Secondly,Zn2+and imidazole were self-assembled on the monolith surface layer by layer.The extraction column took the advantages not only fast mass transfer and good reproducibility from porous monoliths,but also large specific surface area from MOFs.The extraction column significantly enhanced the enrichment factors of fluoroquinolones(FQs)antibiotics by 2.4-3.5 times.An on-line system with HPLC-fluorescence detection was developed for the quantification of FQs in water and honey samples.The LODs were 0.00014-0.00061μg/L and 0.0014-0.011μg/kg,respectively.The proposed method showed good precision.Intra-day assay variabilities exhibited relative standard deviations(RSDs,n=4)lower than 9.8%at different added amounts,and so did inter-day assay.The introduced method was successfully used at water and honey samples for monitoring FQs with good reproducibility(RSDs<10%,n=3),and the recoveries of spiked samples were between 80.1-120%.(3)Magnetic-assisted technique was applied in IT-SPME to improve the extraction efficiency of IT-SPME.A monolithic capillary microextraction column doped with Fe3O4 magnetic nanoparticles was in-situ synthesized.Afterwards,the extraction column was twined with a magnetic coil that was employed to apply variable magnetic field at adsorption and desorption procedure.Based on the magnetic microfluidic principles and the diamagnetism of sulfonylurea herbicides(SUHs),the analytical method of SUHs residues in water and soil samples were developed by coupling the extraction column to HPLC with a diode array detector.The results showed that when magnetic field was applied the extraction efficiencies of SUHs were 82.6-94.5%,which were significantly higher than those(36.8-58.1%)without magnetic field.Using the proposed method for analysis of water and soil samples,the LODs were 0.030-0.15 μg/L and 0.30-1.5 μg/kg,respectively.(4)Magnetic-assisted IT-SPME was used for Cr speciation analysis to provide a new analytical approach for speciation analysis of heavy metals.Cr(Ⅲ)and Cr(Ⅵ)were coordinated with ammonium pyrrolidinedithiocarbamate(APD)to form Cr(Ⅲ)and Cr(Ⅵ)metal organic complexes with properties of UV absorption and diamagnetism.Based on the properties and structure of the complexes,suitable monomer and crosslinker were selected,and a capillary microextraction column doped with Fe3O4 magnetic nanoparticles was prepared and employed as the extraction medium for on-line analysis with HPLC.The preparation and extraction parameters of the column were optimized.The results showed that the extraction efficiencies of the metal complexes were increased from 13.2-24.4%(without magnetic field)to 80.4-86.2%(with magnetic field).The LODs for Cr(Ⅲ)and Cr(Ⅵ)in water samples were 0.0059μg/L and 0.0020 μg/L,respectively,and those in soil samples were 0.47 μg/kg and 0.057 μg/kg,respectively.Satisfactory precision and reproducibility were achieved.The verification experimental results indicated that the proposed method was highly reliable for Cr speciation analysis..