Preparation Of Functionalized Mesoporous Silicas And The Application In Elemental Speciation Analysis

The role and impact of a given element on the environment and living organisms depend primarily on its chemical form.It is necessary to use elemental speciation analysis in studying the propeties of an element.There are many ways to detect trace elements,ICP-MS has been proved to have many advantages:high sensitivity,fast analysis,multi-element capability,etc.The deficiency of these instruments is that they can not discriminate the species of a given element.So,sample pretreatment is necessary before detecting concentration of element by ICP-MS.Solid-phase extraction(SPE)has been used to selectively separate and enrich trace elements in water samples.SPE adsorbents include many material,functionalized mesoporous silica has the characteristics of large specific surface area,adjustable pore size and uniform pore structure.The materials are easily modified with organic functional groups,which show unique advantages in the separation and enrichment of trace element forms.The present work aims at investigating a new SPE material which can overcome the challenges of in-situ separation and enrichment of the trace elementals in water.Novel mesoporous silica materials,functionalized by thiol-and carboxyl-groups,can respectively enrich the specific form of arsenic and chromium selectively,which were used to develop a convenient and efficient in-situ SPE method.Combining with ICP-MS,we achieved the highly sensitive and selective detection of trace arsenic and chromium.1.The synthesis of thiol-group functionalized mesoporous silica and its application in uptake and speciation of arsenicThiol-group functionalized mesoporous silica was synthesized by one-pot co-condensation method.Mercaptopropyltrimethoxysilane(MPTMS)and tetraethoxysilane(TEOS)were used as silicon source,cetyltrimethylammonium bromide(CTAB)as template,and template was extracted.The functionalized silica which has large specific surface area and content of thiol-groups was obtained by adjusting the ratio of silicon reagents and optimizing the content of functional groups.A simple SPE device was prepared with a syringe filter disc containing mesoporous silica.Based on the fact that As(?)can be selectively uptaken by syringe-based solid phase extraction device through chelation in a wide range of pH,while As(V)can not,the separation between As(?)and As(V)was realized.At the same time,the captured As(?)can be eluted and then detected by ICP-MS.This method was successfully applied to detect arsenic in environmental waters.2.The synthesis of carboxyl-group functionalized mesoporous silica and its application in uptake and speciation of chromiumCarboxyl-group functionalized mesoporous silica was synthesized by one-pot co-condensation method.Carboxyethylsilanetriol sodium salt(CES)and TEOS were used as co-structure guide reagent,CTAB as template,and tetrahydrofuran(THF)with hydrochloric acid as solvent to extract template.The functionalized silica which has large specific surface area and content of carboxyl-groups was synthesized by modifying the ratio of silicon reagents and the structure and morphology of material.Carboxyl-group functionalized mesoporous silica was used as SPE sorbent.Based on the fact that Cr(?)can be selectively uptaken by sorbent through electrostatic forces and chelation in a wide range of pH,while Cr(?)can not,the separation between Cr(?)and Cr(VI)was realized.At the same time,the captured Cr(?)can be enriched and detected by ICP-MS.This method was also successfully applied to detect chromium in environmental waters.