| Drugs play an important role in preventing and controlling diseases,reducing mortality and prolonging human life.Drug analysis plays a crucial role in drugs'development,production and application.High performance liquid chromatography(HPLC)has become one of the most commonly used and powerful techniques in drug analysis because of its high separation ability,high sensitivity and high selectivity.Chromatographic column as the separation part of analytes,which is considered to the core of the whole HPLC system.The chemical and physical properties of the phase will determine the mechanisms(reversed-phase,ion-exchange,normal-phase,etc.)of the separation system.Stationary phase is usually prepared by the modification of a specific functional group on the surface of the matrix.Silica is the most popular substrate for the stationary phase of HPLC column for its high mechanical stability and easily modification of the silanol groups by organosilane.Modification of silica with different functional groups is a key step to endow stationary phase with special selectivity.The diversity of the phases is obtained by the surface modification of silica with silane coupling agents.Amino group with multiple properties including high hydrophilicity,hydrogen bond donor/acceptor and are positive charged in certain cases,which makes the amino-functionalized silica exhibit multimodal separation mechanisms including normal-phase chromatography,hydrophilic interaction chromatography and ion-exchange chromatography modes.The amino-functionalized silica can be prepared by liquid-solid method,supercritical fluid reaction and gas-solid reaction method to bonded the amino group on the silica surface.Compared to other methods,the gas-solid method has the advantages of avoiding use of expensive and polluted organic solvents,needing relative simple facilities and more efficiency.However,this kind of phase has a disadvantage of short lifetime,which ascribed to the strongly basic environment comes from the high concentration of amino groups on the phase.The amino groups will erode the silica skeleton and at the same time,hydrolyze the grafted groups in the presence of water.In addition,the retention mechanism of compounds on the amino-functionalized stationary phase is also lacking in systematic study.Based on the above analysis,in this work we revolve around the theme of "a novel highly hydrothermal stability amino-functionalized stationary phase" to establish a green and efficient amino-functionalization method;prepare of amino-functionalized stationary phases with highly hydrothermal stability and long serve life;study chromatographic separation performance,retention mechanisms and broaden these applications.The full text content mainly includes the following aspects:1.A novel gas-solid-impregnation method for the preparation of chemically bonded silica packing was developed independently.The effect of the amount of siloxane reagents on the surface bonding was investigated.And the stability of the bonding phase was verified by Soxhlet's extraction.Then the amino functional silica gel(APS)prepared by this method was characterized by fourier infrared spectroscopy and solid-state 13C MAS nuclear magnetic resonance spectra,and the graft density were quantitatively characterized by elemental analysis.Under the optimized reaction conditions,the amino groups modified by y-aminopropyltrimethoxysilane(APTMS)loading can reach to 3.68 ?mol m-2,which was higher than the 2.95 ?mol m-2 modified by traditional liquid-solid method.There is no obvious change in the amount of the amino group loading after Soxhlet's extraction,indicating that the chemical bonding phase prepared by this method is stable.At the same time,it is found that the APS phase prepared by this method can be used for the analysis of carbohydrates,and the separation is better than the amino-functionalized packing prepared by the liquid-solid method.These results proved the advantage of gas-solid-impregnation method for the preparation of chemically bonded stationary phase.2.A novel bis-trimethoxysilyl-ethane hydrolysis aminopropyltrimethoxysilane(BTME-H-APS)silica stationary phase was prepared through gas-solid-impregnation method.The effect of the amount of ethane bridged regent on the surface bonding and the hydrolysis time of BTME modified silica was investigated.Then the BTME-H-APS phase was characterized by fourier transform infrared spectroscopy,solid-state 13C MAS nuclear magnetic resonance spectra and elemental analysis.The surface density of amino group is up to 3.44 ?mol m-2,which is similar with the commercial amino phase.It was shown the BTME-H-APS stationary phase exhibits a higher hydrothermal stability and longer service life at high alkaline circumstance compare to the commercial amino column.This is due to the relative higher carbon loading and cross-linking degree of the BTME-H-APS phase that was confirmed by the solid-state 29Si NMR.In addition,BTME-H-APS column showed an equal or even higher separation ability in hydrophilic interaction liquid chromatography/reversed-phase liquid chromatography,normal-phase liquid chromatography and ion-exchange chromatography models compared with conventional amino column and performed well on separation alkaloids and carbohydrates.In conclusion,the BTME-H-APS column can be used as a promising alternative to conventional APS column for its increased hydrothermal stability and the equal separation ability.3.A novel bi-ligand bonded stationary phase OAEPS,which is functionalized by octyltrimethoxysilane(OTMS)and(3-(2-)aminoethylamino)propyltrimethoxysilane(AEAPTMS),was prepared through gas-solid-impregnation method.The effects of different ratios of OTMS and AEAPTMS on the surface functional group silica gel composition were investigated.The hydrothermal stability of the mixed-mode OAEPS column was evaluated by an accelerated degradation test.It was shown that the OAEPS stationary phase exhibit a high degree column stability.The chromatographic behavior of OAEPS column was evaluated,results shown that OAEPS column can be used in various modes of chromatography including reversed-phase,hydrophilic interaction and ion-exchange mode.Moreover,the mechanism on this reversed-phase/anion-exchange mixed-mode OAEPS phase was investigated by a systematic study of retention behavior of a homologous series of alkylbenzoic acids.The results demonstrated a three-site model controlled on the phase and the individual contributions from hydrophobic,ionic and cooperative hydrophobic/ionic interactions to the overall retention factors of the solutes were quantitatively assessed.This mechanism study is helpful to optimize the retention and selectivity of a mixed-model column by tailoring ligand density,mobile phase pH,ionic and solvent strength,thus offering enormous flexibility for method development for the separation of complex sample. |
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