Study On The Magnetism-Enhanced In-Tube Solid Phase Microextraction And Its Applications In The Monitoring Of Pollutants

In-tube solid phase nicroextraction(IT-SPME)integrates sample preparation and injection into one procedure.It has drawn much attention in the research field of sample preparation due to the advantages of miniaturization.easy automation and environment-friendliness.Nevertheless,several problems such as low extraction efficiency and long extraction time are found in the applications of IT-SPME.For seeking an effective solution,a new sample pretreatment technique named magnetism-enhanced in-tube solid phase microextraction(ME/IT-SPME)was developed in the present study,which combines the magnetic microfluidic principles,diamagnetism of targeted analytes and the unique merits of monoliths.To demonstrate the practicability,the ME/IT-SPME was coupled to high-performance liquid chromatography with diode array detection(HPLC-DAD)to analyze trace levels of organic pollutants and heavy metal ions(HMIs)in complex samples.The detailed contents are as follows:(1)Modified Fe3O4 magnetic nanoparticles(MNPs)were added into the pre-polymerization solution of monolith,and then the monolithic capillary column doped with MNPs(MCC/MNPs)was synthesized by the in-situ polymerization method.After that,the MCC/MNPs was wrapped with a magnetic coil for the exertion of magnetic fields of different directions and intensities during adsorption and desorption steps.Based on the magnetic microfluidic principles and diamagnetism of analytes,the new ME/IT-SPME method could effectively improve the extraction efficiency of diamagnetic analytes and shorten the extraction time.In order to confirm the validity of ME/IT-SPME,six estrogens were selected as targeted analytes,the effects of key parameters including the intensities of magnetic fields in adsorption and desorption steps,the adsorption and desorption flow rates,the volumes of sample and desorption solvent on the extraction efficiency were studied in detail.At the same time,the extraction mechanism of ME/IT-SPME for analytes was discussed.The results well illustrated that the extraction efficiencies of six estrogens were in the range of 70%-100%under the optimal conditions,which were much higher than those achieved without the application of magnetic fields(i.e.,in the IT-SPME mode)(30%-65%).These results indicate that the magnetic field plays an important role in the enhancement of extraction for analytes.Finally,the developed ME/IT-SPME was applied to the determination of trace estrogens in environmental water samples by combination with HPLC-DAD.The accuracy and feasibility of the proposed method were verified by the recovery and confirmatory experiments(2)A poly(octyl methacrylate-co-ethylene dimethacrylate)-based MCC/MNPs(poly(OM-co-ED)-MCC/MNPs)was prepared by using OM and ED as functional monomer and crosslinker,respectively.The poly(OM-co-ED)-MCC/MNPs was characterized by fourier transform infrared spectroscopy,magnetic analysis,scanning and transmission electron microscopy,etc.,and then used to extract six triazines(TRs)in virtue of the ME/IT-SPME mode.Under the optimized conditions,the extraction efficiencies of targeted TRs were in the range of 65%-100%,which were much higher than those achieved in the IT-SPME mode(26%-85%).At the same time,the ME/IT-SPME was combined with HPLC-DAD to detect trace TRs in environmental water samples.The limit of detection(LOD,S/N=3)and limit of quantification(LOQ,S/N=10)values were in the ranges of 0.07-0.23 ?g/L and 0.24-0.75 ?g/L,respectively.The developed method was successfully applied to analyze targeted TRs in lake,river and farmland water samples,with spiked recoveries ranging from 70.7%to 119%.(3)In order to extract UV filters in environmental water samples effectively,an ionic liquid,namely 1-allyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imid was used as functional monomer to copolymerize with ED to obtain a polymeric ionic liquid(PIL)-based MCC/MNPs(PIL-MCC/MNPs).The physicochemical characteristics of PIL-MCC/MNPs were analyzed by a series of characterization techniques.Under the most favorable conditions,the extraction efficiencies of five targeted UV filters were in the range of 44%-100%,the corresponding values achieved in the IT-SPME mode were 11%-62%.The PIL-ME/IT-SPME was online combined with HPLC-DAD to detect trace levels of UV filter residues in environmental water samples.The LOD(S/N=3)and LOQ(S/N=10)values were in the ranges of 0.04-0.26?g/L and 0.12-0.87 ?g/L,respectively.Good precision in terms of intra-day and inter-day relative standard deviation(RSD)values less than 10%was obtained.Compared with other analytical metihtods for UV filters,the proposed method displays some advantages such as rapidity,low consumptions of sample and organic solvent,cost-effectiveness and environmental friendliness.(4)To demonstrate the feasibility of ME/IT-SPME in the enrichment of HMIs,Co(?),Cu(?)and Hg(?)were selected as targeted analytes.After complexing with the chelating agent sodium diethyldithiocarbamate(DDTC),the targeted Co(?),Cu(?)and Hg(?)were derived into diamagnetic metal-organic complexes(i.e.,Co-DDTC,Cu-DDTC and Hg-DDTC).According to the chemical structures of complexes,the poly(4-vinylphenylboronic acid-co-ED)-based MCC/MNPs(poly(VA-co-ED)-MCC/MNPs)was fabricated by the in-situ polymerization of functional monomer VA and crosslinker ED,and then used as microextraction column of the online ME/IT-SPME-HPLC-DAD analytical system.Under the optimum conditions,the extraction efficiencies of Co-DDTC,Cu,DDTC and Hg-DDTC were enhanced from 47%-65%(in the absence of magnetic field)to 67%-89%.For water sample,the LOD(S/N=3)and LOQ(S/N=10)values were in the ranges of 0.0043-0.035 ?g/L and 0.014-0.12?g/L,respectively.For seafood sample,the corresponding values were 0.69-4.9 ?g/kg and 2.2-16?g/kg,respectively.In addition,good precision and reproducibility were achieved.The proposed online analytical approach was successfully applied to the determination of three targeted HMIs in environmental water samples and Co,Cu,Hg elements in seafood samples(fish and shrimp).The detected results were verified by the confirmatory experiments with reference methods.The present study further expands the application of ME/IT-SPME.At the same time,it provides a simple,sensitive and cost-effective analytical method for HMIs.