Enrichment Of Perfluorinated Carboxylic Acids, Derivatized, And GC-MS Analysis

The human society is developing and progressing continuously, and more and more pollutants are associated to appear in the natural and social environment. Perfluorinated carboxylic acid compounds (PFCAs) have become a global environmental problem gradually because of its high stability, bioaccumulation effect and widely existence. It is also a hot spot of persistent organic pollutants (pops) research. In recent years, the researchers have studied on the environmental behavior, toxicity and present pollution situation of PFCAs. But the report about sample pretreatment for PFCAs is less. Because the PFCAs concentration in environmental samples is extremly low so that the effective enrichment and to establish the universal analysis method is particularly important. The perfluoroalkyl modified stir bar and magnetic microspheres are prepared to enrich PFCAs, then carryed on precolumn derivatization, we have set up an gas chromatography-mass spectrometry technology for rapid analysis of PFCAs.This article includes the following content:Chapter one ReviewFirst, we have summarized the research background of Perfluorinated carboxylic acids (PFCAs), which included the properties of PFCAs and the necessity to study PFCAs. After that, the enrichment methods and the detection methods of PFCAs had been introduced. Finally, the derivatization methods and reagents which used for PFCAs had been summarized, especially the GC-MS method.Chapter two Preparation and characterization of perfluoroalkyl modified stir bar and magnetic microspheresThe magnetic stir bar modified by1H,1H,2H,2H-perfluorodecyltrichlorosilane based on chemical bonding. We have optimized the preparation condition which includes the reaction time, reaction temperature, drying time and so on. And then the modified bar have been characterized by EDX. The result indicated that the stir bar was successful modified with1H,1H,2H,2H-perfluorodecyltrichlorosilane and the surface of the stir bar was enriched with F. The optimum condition is reaction at70℃for7h, drying at60℃for6h and curing at70℃for6h under vacuum.The Fe3O4magnetite microspheres are synthesized by solvent-thermal method, then Fe3O4@SiO2microspheres were prepared via a classical Stober route, and finally use1H,1H,2H,2H-perfluorodecyltrichlorosilane to perfluoroalkyl-functionalize magnetic microspheres.The microspheres were characterized by SEM and EDS.The results indicated that the Fe3O4microspheres was with uniform size approximately330nm. The surface of the microspheres was successful modificated with silica and perfluoroalkyl in turn.Chapter three The GC-MS precolumn derivatization of PFCAsThe paper Using chloroformic acid butyl ester as derivatization reagent, isobutanol as auxiliary reagentand pyridine as catalyst.After precolumn derivatization, the PFCAs derivatives are separated and detected by GC-MS.We also investigated the impact of the reaction time,reaction temperature and the dosage of reaction reagents.The GC and GC-MS detecting conditions have been investigated simultaneously. The optimum condition is reaction at room temperature for15min and the reaction reagent content is10μl of chlorine formic acid butyl ester,5μl of isobutanol and5μl of pyridine. Under the optimal conditions, the detection limit range is1.3-6.2μg/L, RSD range is from2.5%to5.7%, the PFCAs have good linear relationship in10-5000g/L.Chapter four The adsorption properties of perfluoroalkyl-functionalized stir bar and magnetic microspheresWe optimized the adsorption pH, ionic strength, adsorption time, eluent, and elution volume of magnetic stir bar on the adsorption and desorption of PFCAs.The optimum condition is in solution pH4, ionic strength about100mmol/L, the adsorption time40min. The best desorption condition is used0.1%ammonia methanol elution1.5mL×4,one time10min. For magnetic stir bar, the correlation coefficients were greater than0.99, RSD is in the range of6.8%to9.8%, the linear range at0.5-10μg/L, detection limit range from0.068to0.11μg/L.The paper investigated the adsorption properties of perfluoroalkyl-functionalized magnetic microspheres on PFCAs simultaneously.After enriched, the PFCAs derivatized with chloroformic acid butyl ester. Then the Derivative products were separated and detected by GC-MS. The correlation coefficients were greater than0.99, RSD is in the range of6.2%to9.4%, the linear range at0.5-10μg/L, detection limit range from0.063to0.11μg/L.