Research And Application Of Solid-phase Microextraction Tube Based On Melamine-formaldehyde Aerogel Coating

In recent years,solid-phase microextraction?SPME?has been developed as a popular sample preparation technique,which has been widely used in biology,environment,food and so on.In-tube SPME as a special form is not only easy to operate and has high precision,but also convenient for online combination with high performance liquid chromatography,it achives on-line,fast and highly sensitive analysis.The key of in-tube SPME is the extraction coating.The material with high specific surface area and good adsorption performance is the first choice for the development of efficient extraction coating.Aerogels are potential extraction materials due to its high specific surface area and porosity,and good adsorption performance.In this paper,melamine-formaldehyde?MF?aerogel was used as a base material for organic modification and inorganic hybridization.The functionalized aerogel coatings were prepared on the surface of carbon fibers,and then the fibers were packed into polyetheretherketone?PEEK?tube to develop new SPME tubes filled with fibers.In order to realize the online extraction and chromatographic analysis,the loop on the six-port valve was replaced by the extraction tube,and a sample transfer pump was also connected.It can provide simple,fast and sensitive online analysis methods for the detection of important organic pollutants in environmental water samples.The main research contents are as follows:1.The MF aerogel was modified by polydopamine and prepared on the surface of carbon fibers as an extraction material.The high adhesion of polydopamine with the surface of the substrate provided sufficient guarantee for the stability of the aerogel coating.The PEEK tube with an inner diameter of 0.75 mm and an outer diameter of 1.5 mm was used to pack the extraction material,and the surface structure of the extraction material was characterized by scanning electron microscopy?SEM?.Coupled with high performance liquid chromatography?HPLC?,online in-tube SPME-HPLC system was built.The phthalates were selected as the targets,the several important factors such as extraction volume,extraction flow rate,organic solvent content and desorption time were optimized.An analysis method was established with low detection limits(0.02-0.05?g L^-1)and wide linear ranges(0.07-30?g L^-1),the spike recoveries of real samples were in the ranged of 77%-120%.Compared with other reported methods based on various extraction materials,the proposed method had relatively satisfactory advantages in terms of detection limits,enrichment factors and extraction time for phthalates.2.An imidazole ionic liquid was synthesized and used to functionalize MF aerogel.An ionic liquid functionalized MF aerogel coating was prepared on the surface of carbon fibers.Ionic liquid improved the extraction efficiency of MF aerogel.The surface of the extraction material was characterized by SEM and energy spectrum.The results showed that the three-dimensional network structure of the aerogel was obvious and the ionic liquid was successfully modified in the coating.The extracted material showed better selectivity for estrogens.Combined with HPLC,online in-tube SPME-HPLC system was built and the factors affecting the extraction efficiency were optimized.Under optimal conditions,the detection limits were 0.05-0.20?g L^-1,reproducibility were 0.3%-2.5%?intraday?and 6.2%-10.5%?interday?.Good stability of extraction tube was also exhibited.The establsied method was suitable for the analysis of real sample.The analytical method is relatively superior to other analytical methods in both detection limits and extraction times.3.Different proportions of titanium dioxide sol and MF aerogel were mixed,and TiO₂doped MF aerogel was prepared on the surface of carbon fibers.The extraction materials were characterized by SEM.The best reaction ratio was obtained and high selectivity for PAHs was shown through the investigation of extraction performance.The extraction tube based on the new aerogel coating was combined with 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^-1,good spike recoveries and stability of the extraction tube indicated that it can be applied to the analysis of real samples in the environment.