Application Of Novel Carbon Nanomaterials In Solid Phase Microextraction And Gas Chromatography Stationary Phase

Solid phase microextraction（SPME）is a balance-based,solvent-free sample preparation technology that integrates sampling,extraction and preconcentration,and is a hotspot in the field of analytical chemistry.SPME fiber coating is the core component of SPME technology.The choice of coating material is the key to achieve high-efficiency extraction,but it has the following disadvantages:poor mechanical properties,time-consuming preparation process,easy to fall off coating,short lifetime,not resistant to temperature and not resistant to organic solvents,etc.Therefore,the development of coating materials with high stability,high adsorption efficiency,and good selectivity,and the development of simple and rapid preparation of coated fibers have become hot topics in the field of sample preparation.In addition,in gas chromatography,capillary gas chromatography stationary phase as the core and key of gas chromatography analysis,preparation and research of various thermal stability,high efficiency,high selectivity of stationary phase is an important task for chromatographers.Based on the above research background,this study focused on the research of SPME fiber material preparation and capillary gas chromatography stationary phase performance testing and evaluation,which include the following sections:1.Porous graphene（PG）,a type of graphene-based material with some holes/pores with in the atomic plane,has recently attracted great attention.In this study,PG was prepared by combustion method and used as a new coating on stainless-steel fibers for direct immersion solid-phase microextraction（SPME）of polycyclic aromatic hydrocarbons（PAHs）.Compared to polydimethylsiloxane-coated fiber,PG-coated SPME fiber showed higher enrichment factors（EFs）,which increased with the number of aromatic rings.The excellent extraction ability was mainly due to the existence of nanopores.Moreover,PG also providedπ–πstacking interaction and hydrophobic properties for better extraction efficiency of aromatic compounds.Additionally,PG-coated fibers exhibited good precision（<8%）,wide linear ranges(0.002–10μg L^-1),and low limits of detection(1ng L^-1)for PAHs.The results verified that this novel PG coating was a promising sorbent for extraction and trace analysis of PAHs in environmental water samples.2.Porous graphene is a novel gas chromatographic stationary phase for the efficient separation of gases,liquid hydrocarbons,fatty alcohols,and BETX.The analysis results show that the separation of benzene and cyclohexane from the porous graphene stationary phase is superior to that of the commercial column.Both hydrocarbons are nonpolar,but an unsymmetrical charge distribution can be induced in benzene due to the easily shiftableπ-electrons.Prior to cyclohexane,the benzene eluted first according to its boiling point,indicating the delocalized largeπbond interaction between benzene and porous graphene.However,complete separation cannot be achieved in the non-polar stationary phase.The PG stationary phase exhibited good heat setting properties at 300°C.In addition,the porous graphene capillary GC column exhibits good accuracy and reproducibility.3.Covalent Organic Polymers（COPs）are a class of high molecular polymer materials with microporous or mesoporous structures linked by covalent bonds.They have unique properties and applied in energy,gas storage,and photoelectric conversion,etc.al.However,there are few reports on the use of COPs for gas chromatography（GC）separation.In this work,we synthesized a new spherical COPs and defined it as（Covalent Organic Nanosphers,CONs）,and we applied a static vacuum method to the capillary column.The prepared column showed non-polarity and the column efficiency of naphthalene was as high as 2796 plate m^-1.CONs coated gas chromatography columns show high separation performance of a range of polar,non-polar compounds,including challenging cyclohexanone and heptanone,pentanol isomers,nitrotoluene,and nitroaniline isomers.Selective comparison of commercial CB-5 stationary phases.In addition,the retention time of the relative standard deviation of the five replicate measurements of the analyte during the day and the inter-column investigation were investigated.To study the interaction between some analytes and the stationary phase,thermodynamic parameters were also evaluated.The results of this study indicate that the use of COPs as a stationary phase for capillary GC is very promising.Compared to commercial column CB-5,CONS coated gas chromatography columns show high separation performance of a range of polar,non-polar compounds,including challenging cyclohexanone and heptanone,high selectivity of pentanol isomers,toluene and nitroaniline isomers.In addition,it was evaluated by column reproducibility,quantitative analysis ability,and thermal stability of the CONs column,which showed good accuracy,reproducibility,and thermal stability.The above results indicate that CONs is an ideal choice for use as a stationary phase for capillary GC.