The Development Of Novel Solid-phase Microextraction Coatings And The Application In Environment Analysis

Solid-phase microextraction(SPME) is one kind of important sample preparation technology which has been widely used in fields like environmental monitoring, biology analysis, food safety and forensic test. Now it’s more and more difficult to meet the analysis requirements of different fields for the several commercial SPME fibers because of their frangibility, thermal instability, poor selectivity and high cost. In this study, microextraction technique, including the origin, development, theories, coatings and applications of electrochemical method in SPME was systematically introduced. Then the research conception is introduced.Then we have prepared ZnO nanorods/Polyaniline(ZNRs/PANI) composite coating on a stainless wire using electrochemical deposition and in-situ hydrothermal growth method.Scanning electron microscopy(SEM) study revealed that the majority of oriented ZNRs grew from pores of PANI matrix, which protected the ZNRs from easily peeling off during operation. Furthermore, in this process, a thin layer of PANI was found to cover the ZNRs,which can enlarge the effective surface area of the composite coating. This ZNRs/PANI composite coating combined the merits of both ZNRs and PANI and, thus, has several advantages over that of sole PANI film and ZNRs coating such as improved extraction efficiency for benzene homologues, enhanced mechanical stability and longer service life.Coupled with gas chromatography-flame ionization detector(GC-FID), the coating was used to extract six benzene homologues and the conditions that might affect the extraction efficiency were optimized. A SPME-GC-FID method was established for the analysis of benzene homologues in real water samples.In addition, MSU-H mesoporous silica was synthesized using P123 as a “soft template”.Then ordered mesoporous carbon(OMC) similar to the anti-structure of the template wasfabricated using sucrose as a carbon precursor and MSU-H as a “hard template”. The physicochemical properties of the as-synthesized OMC were studied. The surface area of1019 m2·g-1, the pore volume of 1.46 cm3·g-1and the most probable pore size of 4.2 nm was obtained from a gas adsorption analyzer. The crystal structure of OMC was proved to be ordered hexagonal structure by X’ pert PRO powder diffraction system. Clearer figures of the pore structure and arrayed rule of OMC powder were obtained from a transmission microscopy. In addition, the thermal stability of OMC was tested on a differential thermal analyzer and it indicated that OMC was still thermal stable even the temperature was as high as 850 oC.Then OMC was immobilized onto a stainless steel wire using Nafion as a binder to prepare an OMC/Nafion SPME coating. The images of scanning electron microscope showed the thickness of the proposed coating was about 30 m, and OMC composed of rough wormlike particles were arranged in Nafion uniformly. Next, the thermal stability of OMC/Nafion coating was investigated. Then, the extraction characteristics of the OMC/Nafion coating were extensively studied using a wide range of analytes including week polar(petroleum ethers and benzene homologues) and strong polar compounds(phenols and alcohols). The OMC/Nafion coating was found to exhibit much better extraction efficiency towards all the analytes selected compared to that of a multi-walled carbon nanotubes(MWCNTs)/Nafion coating with the same length and thickness. Such excellent extraction ability was ascribed to the high surface area, well-ordered mesoporous structure and large pore volume of the OMC. In addition, the OMC/Nafion coating possesses excellent extraction selectivity and good immunity from interference towards aromatic non-polar compounds,probably due to the hydrophobic surface and !-! stacking structure of the OMC. The feasibility of the OMC/Nafion coating in the application of electrochemically enhanced SPME was also demonstrated using protonated amines as model analytes.The two SPME coatings prepared in this study have the necessary characteristics and their own unique advance that comply with the development trends and application requirements. They have very great potentialities in the future environment analysis filed.