Preparation Of Ordered Mesoporous Carbon Coating For Solid-phase Microextraction And Its Determination Of Chlorobenzenes In Water

Solid-phase microextraction(SPME), a new pre-processing techniques for organic analysis, has been applied widely in environmental monitoring because of its simple, convenient, solvent-free and green. The coating is the core part of the SPME technology. However, the commercial coatings show some drawbacks such as lower thermal and chemical stability, short life and high cost. So the development of a simple and efficient coating has great significance. This work was aimed to preparing a pure inorganic, one-step ordered mesoporous carbon (OMC) coating against the issues of low thermal and chemical stability and complicated process for inorganic SPME coating. The OMC coating is assessed by SPME-GC technique with chlorobenzenes compounds as model. The main contents are as follows:The OMC coating supported on graphite fiber for SPME was prepared by combining evaporation-induced self-assembly (EISA) process with dip-coating method. The OMC coating thickness was controlled through different dip-coating times. Thermal analysis and infrared spectroscopy shows the formation process of the OMC. The structure and morphology of the OMC coating were characterized by scanning electron microscopy, transmission electron microscopy, x-ray diffraction and nitrogen adsorption-desorption. The results show that the OMC coating is complete and combine with the matrix tightly. Controlled thickness of the coating is at the range of 2.5μm～11.25μm. The structure of the pore has a regular two-dimensional hexagonal features and specific surface area and pore volume are 369.7m2/g and 0.28cm3/g, respectively.The SPME performance of the OMC coating was evaluated by analysis of four kinds of chlorobenzenes from water samples using headspace SPME-GC-FID method. The thickness of coatings plays a key role for the extraction capacity and sensitivity. When the thickness is 7.1μm, the highest extraction efficiency can be obtained. The analysis condition, including extraction time and temperature, desorption time, stirring rate, ionic strength and headspace volume, were optimized. Moreover, the SPME performance home-made coating was compared with the commercial coatings. The analysis results indicate the prepared OMC fiber demonstrates wide linear ranges (1～1000μg/L) and low detection limits (0.05～0.15μg/L) under the optimal extraction conditions for extraction time of 30 min, extraction temperature of 50℃, desorption time of 2 min, stirring speed of 1200 r/min, salt concentration of 0.35 g/mL, headspace volume of 25 mL. The relative standard deviations were 4.1%～6.4% for seven parallel samples. The extraction efficiency of the OMC coating is 2 times more than PDMS/DVB coating and 18 times more than PA coating. The performance of the OMC coating was evaluated. The results confirm that its thermal/chemical stability and life had improved significantly. The OMC coating was applied to two real water samples, four chlorobenzenes were not detected. The recoveries of two samples spiked at 20μg/L were in the range of 96%～113.6% and 87.7%～97.8%, respectively.