| Most heavy metals are highly toxic at a low concentration and have tendency towards bioaccumulation to.plants,animals and human beings.Long-term exposure to the environment polluted by heavy metal would cause serious harm to the human body.Studies have shown that the behavior and toxicity of an element depends primarily on its presence in the environment rather than its total amount.Due to the low content of toxic metals in the environment and the variability of elemental morphology,the elemental speciation analysis and related fields has received extensive attention and become a challenging research area.Conventional trace element detection techniques,such as inductively coupled plasma mass spectrometry(ICP-MS),can only detect the total amount of elements,but cannot distinguish the speciation of the elements.Thus it is necessary to combine element detection techniques with pre-separation technologies,like solid phase extraction and solid phase microextraction(SPME).Organic-inorganic hybrid monolithic columns have the advantages of high mechanical strength,good biocompatibility,wide pH application range.Not only that,they are also known as no need for plungers,simple operation,small sizes,easy to carry,and can be used on site,which make them ideal SPME matrix.Therefore,it is of great significance to develop novel organic-inorganic hybrid monolithic columns which are suitable for elemental speciation analysis.The present work aims at investigating novel organic-inorganic hybrid monolithic columns and constructing needle SPME devices for the speciation separation analysis of trace elements.On the basis of developing and improving the preparation methods of single functionalized hybrid monolithic column,the novel multi-functionalized hybrid monolithic columns were explored and prepared.Fast,efficient and speciation-friendly SPME-ICP-MS analysis methods for the element speciation separation analysis were established.The major contents are described as follows:1.A needle-SPME device was constructed using an amino-functionalized hybrid monolithic column for separation and enrichment of inorganic arsenic in environmental water.The amino-functionalized organic-inorganic hybrid monolithic column was prepared by "one-pot" sol-gel method using tetraethylorthosilicate and N-(2-aminoethyl)-3-aminopropyltriethoxysilane as silane reagents.A needle SPME device was constructed by replacing the portion of the needle in the syringe with the amino monolithic column.Due to the electrostatic interaction between the amino groups and As(V),As(V)can be selectively extracted by the monolithic column and measured by ICP-MS after eluted by HNO3.The established method is suitable for separation and enrichment of inorganic arsenic species in environmental water and can be used on site,which can not only reduce the workload of transporting water samples back to the laboratory,but also avoid the change of arsenic species in the process of transportation and storage.2.A novel thiol-functionalized organic-inorganic hybrid monolithic column was synthesized using an unconventional ternary weak basic solvent system via one-step sol-gel process.The preparation conditions,such as the ratio of silane reagents and the amount of mixed solvents,were optimized in detail.The morphology and chemical properties of monolith were systematically characterized.The thiol-functionalized monolithic column synthesized by this method has good permeability and mechanical strength,and the distribution of thiol groups is more uniform.The needle SPME device based on this monolithic column can selectively capture As(III)without adsorbing As(V)in a wide pH range.The proposed method had good separation and analysis properties for inorganic arsenic species,and can be directly achieved on site for pretreatment of environmental water samples.3.Simultaneous speciation analysis of chromium and antimony was achieved by using a novel carboxyl-functionalized organic-inorganic hybrid monolithic column(TMOS-co-CES)prepared via one-pot co-condensation of carboxyethylsilanetriol sodium salt and tetramethoxysilane.Various parameters of preparation conditions were investigated systematically.The adsorption behavior of the TMOS-co-CES column on inorganic chromium and antimony was studied.This column was also compared with the thiol monolithic column on separation and enrichment of antimony.It was found that the TMOS-co-CES column can selectively adsorb the low-valent Cr(?)and Sb(?),with the advantages of milder elution condition and higher recovery for antimony species,which was more friendly to ICP-MS instrument.4.A novel thiol-and amine-bifunctionalized hybrid monolithic column was prepared via one-pot process.The monoliths were more tightly attracted to the capillary by enhancing the concentration of pretreating NaOH and HCl.The bifunctional material is capable of adsorbing As(?)and As(?)by coordination and electrostatic action respectively.The elution mechanism of As(?)and As(?)were explained and a non-aggressive eluent for As(?)was proposed based on chelation rather than oxidation,which could desorb As(?)without changing the speciation of As(?)or destroying active sites on monolithic column.The bifunctionalized monolithic column can be used for separation and enrichment of speciation of inorganic arsenic with the method of "simultaneous adsorption and stepwise elution"by needle-SPME.5.An amino-and carboxyl-biffuctional hybrid monolithic column was synthesized by a "one-pot" using double porogens.The effects of different porogens on the morphology of the monolith and the adsorption behavior of the material on two inorganic chromium species were studied.Various parameters of SPME operation and detection were also investigated systematically.The monolith can selectively adsorb Cr(?)and Cr(?)under different pH conditions.A needle SPME method for the rapid separation and enrichment of inorganic chromium species in environmental water samples was established by means of "conditional adsorption" and combining with low-invsive eluent. |
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