Studies On The Preparation And Application Of Novel Solid-phase Microextraction Fibers Based On Sol-gel Technology

Solid-phase microextraction(SPME) has been proved to be a widely used sample-preparation method with simple, fast and solvent-free characteristics. It combines sampling, extraction and preconcentration of the analytes into a single step and enables direct desorption of the analytes into the chromatographic systems for analysis. Although several commercial SPME fibers are commercially available, however, they still have some drawbacks, such as easy breakage of the fiber, stripping of the coating, swelling in organic solvents and limited variety of the commercial fibers. Therefore, the development of novel coating materials to achieve an efficient extraction of the analytes has attracted much research attention.The recent development of the SPME fiber coatings were briefly summarized in the first part. A detailed review concerning several novel SPME coating materials and the fiber coating preparation technology were presented.In the second part, polydimethylsiloxane/metal-organic frameworks were immobilized onto a stainless steel wire through sol-gel technique as SPME fiber coating. The prepared fibers were used for the extraction of some polycyclic aromatic hydrocarbons(PAHs) from water samples prior to gas chromatography-mass spectrometry. Under the optimized experiment conditions, the PDMS/MIL-101 coated fiber exhibited higher extraction efficiency towards PAHs than that of PDMS/MOF-199. Several parameters affecting the extraction of PAHs by SPME with PDMS/MIL-101 fiber, including the extraction temperature, extraction time, sample volume, salt addition and desorption conditions, were investigated. The limits of detection(LODs) were less than 4.0 ng/L and the linearity was observed in the range from 0.01 to 2.0 μg/L with the correlation coefficients(r) ranging from 0.9940 to 0.9986. The recoveries of the PAHs from water samples at spiking levels of 0.05 and 0.2 μg/L ranged from 78.2% to 110.3%. Single fiber repeatability and fiber-to-fiber reproducibility were less than 9.3% and 13.8%, respectively.In the third part, a polydimethylsiloxane/graphene composite was coated onto etched stainless steel wire through sol-gel technique and it was used as a SPME fiber. The prepared fiber was characterized by scanning electron microscopy, which revealed that the fiber had a highly porous structure. The application of the fiber was evaluated through the headspace SPME of five halogenated aromatic hydrocarbons in water samples followed by gas chromatography-flame ionization detection. Under the optimum conditions, the linearity of the method ranged from 2.5 to 800.0 μg/L for 1,2,4-trichlorobenzene and from 2.5 to 500.0 μg/L for chlorobenzene, bromobenzene, 1,3-dichlorobenzene and 1,2-dichlorobenzene, with the correlation coefficients(r) ranging from 0.9962 to 0.9980, respectively. The limits of detection(S/N = 3) of the method for the analytes were in the range between 0.5 and 1.0 μg/L.In the fourth part, a tetraethyl orthosilicate/graphene composite coated stainless steel SPME fiber was prepared. The application of the fiber was evaluated through the extraction of five acetanilide herbicides in water samples followed by gas chromatography-electron capture detection. The linear response for the analytes was observed in the range from 0.8 to 150.0 μg/L with the correlation coefficients(r) ranging from 0.9933 to 0.9970. The limits of detection(LODs) were less than 0.10 μg/L. The single fiber repeatability and fiber-to-fiber reproducibility were less than 6.2% and 11.2%, respectively. The recoveries of the acetanilides from water samples by the current method at spiking levels of 1.0, 10.0 and 100.0 μg/L fell in the range from 81.8% to 112.0%.In the fifth part, SPME coupled with gas chromatography–mass spectrometry was developed to determine trace levels of nitrobenzene compounds in water and soil samples. Graphene was chosen as the extraction material and its composite was coated on a stainless steel wire through sol-gel technique for the SPME. The key parameters influencing the extraction efficiency were optimized. Under the optimal conditions, the linearity for the compounds was observed in the range of 0.02~15.0 μg/L for water samples, and 0.2~60.0 μg/kg for soil samples, with the correlation coefficients(r) of 0.9966~0.9987. The limits of detection of the method were 0.0025~0.005 μg/L for water samples, and 0.02~0.04 μg/kg for soil samples. The recoveries for the spiked samples were in the range of 72.0%~113.2%, and the precision, expressed as the relative standard deviations, was less than 12.1%.