Mesoporous Silica Materials Functionalized With Carbon For Solid-phase Microextraction

Solid-phase microextraction(SPME)has been developed into a significant sample pretreatment technology,which is extensively employing in food,environment,biology,and drug analysis.In-tube solid-phase microextraction(IT-SPME),as a particular form of SPME,not only has the advantages of simple operation and high accuracy,but also can be easily combined with high performance liquid chromatography to achieve fast,online,highly sensitive and selective detection.It overcomes the common defects of fiber SPME,such as low adsorption capacity,brittleness,bending problems,short life span and sample loss during operation.Materials with excellent extraction performance,large surface area and high chemical stability are good choices for IT-SPME coatings.Mesoporous silica functionalized with carbon materials has been developed as a potential type of microextraction material due to their porosity,high specific surface and adsorption property.1.In the first work,the mesoporous material was coated on stainless steel wires,and three wires were inserted inside of a polyetheretherketone tube for IT-SPME.The tube was coupled to high performance liquid chromatography with diode array detection to obtain an online analytical system,then its extraction performance was evaluated using eight polycyclic aromatic hydrocarbons(PAHs)as the targets.In order to obtain good sensitivity,four conditions were optimized such as sampling volume,sampling rate,methanol content in the sample and desorption time.Under the optimum conditions,an online analytical method was established and exhibited low limits of detection from0.005 to 0.050 ?g/L,a wide linear range of 0.016-20.00 ?g/L with acceptable correlation coefficients in 0.9921-0.9999,as well as large enrichment factors in the range of 311-2412.The method was successfully applied to determine trace PAHs in some real water samples including two kinds of bottled water,tap water and river water,a few PAHs were detected but none quantified in these samples.2.In the second work,mesoporous silica was modified with ordered mesoporous carbon for solidphase microextraction.Three stainless steel wires coated with the mesoporous material were placed in a polyetheretherketone tube for getting an extraction tube.The tube was coupled to high performance liquid chromatography with a diode array detector,and the online analysis system was constructed.Then its extraction performance was evaluated using hydrophobic PAHs,phthalates and hydrophilic neonicotinoids.The best selectivity was presented for PAHs.Several main conditions were optimized such as sampling volume,sampling rate,methanol concentration in the sample and desorption time,a rapid and sensitive analytical method was established towards PAHs.The analytical method exhibited a wide linear range from 0.017 to 15 ?g/L with acceptable correlation coefficients more than 0.9990,limits of detection in 0.005-0.020 ?g/L,limits of quantification ranging from 0.017 to 0.066 ?g/L as well as large enrichment factors of 377-2314.It was successfully applied to detect trace PAHs in some real water samples,including tap water,snow water and domestic sewage.3.In the third work,the mesoporous silica was modified by graphene oxide to improve the extraction performance and the coating material was prepared on the surface of three stainless steel wires and were placed in a polyetheretherketone tube for getting an extraction tube.The surface of the extraction material was characterized by TEM,SEM,BET and energy spectrum.The results showed that the mesoporous structure of the mesoporous silica was obvious and the graphene oxide was successfully modified in the coating.The extracted material showed better selectivity for hydrophobic PAHs.Combined with HPLC,an online IT-SPME-HPLC system was built and the factors affecting the extraction efficiency were optimized.Under optimal conditions,the detection limits were 0.005-0.20 ?g/L,reproducibility were 0.3%-4.5%(intraday)and 0.9%-6.8%(interday).The good stability of the extraction tube was also exhibited.The established method was suitable for the analysis of real samples.The analytical method is relatively superior to other analytical methods in both detection limits and extraction times.4.In the last work,porous carbon was deposited onto mesoporous silica nanospheres to improve extraction efficiency.Extraction material was coated on the surface of three stainless steel wires and were placed in a polyetheretherketone tube for getting an extraction tube.The extraction material was characterized by SEM.The high selectivity for PAHs was shown through the investigation of extraction performance.The extraction tube based on the new coating was coupled to HPLC,the extraction and desorption conditions were optimized,and the analytical method was established under the optimal conditions.The detection limit was as low as 0.05 ?g/L,good spike recoveries and stability of the extraction tube show that it can be used for the analysis of real samples.