Applications Of ILs-based Solid-Phase Microextraction Coating In Monitoring And Assessing The Bioavailability Of Organophosphate Esters

Solid phase microextraction (SPME) is one of popular sample preparation techniques, which can integrate sampling, extraction, preconcentration and sample introduction into a single step. SPME is solvent free, easy to handle and sensitive. Commerical fibers have to suffer several drawbacks such as phys-chemical instablity, short lifespan and high price. Therefore, development of novel SPME fibers with good stability, high extraction efficiency, low cost has been one of the hotspots for SPME technique. Among the fiber preparing technologies, sol-gel coating technology provides a simple and convenient approach to prepare SPME coatings. In comparison with the fibers produced by conventional coating technologies, the fibers prepared by sol-gel technology have many advantages, such as strong adhesion of the coating to the substrate due to chemical bonding, high stability, large surface area and low cost. Sol-gel technology is becoming increasingly popular in preparing SPME fibers. In addition, ionic liquids (ILs) have emerged as increasingly popular SPME coatings owing to their fascinating properties including low volatility, good thermal stability and excellent extraction capability for various organic compounds and metal ions. The IL-based SPME coating could combine the advantages of liquid pahse extraction and solid phase extraction, therefore, the preparing of ILs-based SPME coating is a spot of research at present.Organophosphate esters (OPEs), which are widely used as flame retardants and plasticisers in a variety of products, have been used extensively on a large scale worldwide for several decades. Because OPEs are used as additives that are just mixed and not chemically bonded with the materials, OPEs can easily be released from the materials to the surrounding environment. The analysis of OPEs in environmental media is therefore a hot spot of analytical research at present. Until the present, a number of pretreatment techniques have been attempted to extract OPEs, but all of them have to suffer lots of drawbacks. SPME has been recently considered to be an attractive, valuable, time-and cost-effective technique to replace these conventional methods for extracting OPEs. However, all the relevant studies used commercial fibers, which are expensive and still not suitable for the whole range of OPEs, because of the low recovery and unacceptable deviations of tri(2-ethylhexyl) phosphate (TEHP). Thus, to improve the performance of SPME for OPEs, novel fibers must be developed. Besides, the research mostly focuses on the analysis of OPEs, and there is no report about the bioavailability of OPEs which can provide the theoretical basis for the correct evaluation of the risk and the development of environmental standards and environmental rehabilitation. Main contents and results are as follows:(1) [AMIM][BF4]-based sol-gel SPME fiber was prepared by sol-gel technology in this study. The surface, thermal and chemical stability, lifetime, repeatability and extraction capability of the coating were studied. The result shows that the developed coating was nanoporous and performed stably at high temperatures (up to 335 ℃) and with a range of solvents. It can be used at least 200 times without an obvious decrease in the extraction efficiency. The extraction capacity of the prepared coating is higher than the commercial fibers, 1-allyl-3-methylimidazolium hexafluorophosphate ([AMIM][PF6])-based and 1-allyl-3-methylimidazolium bis(trifluoromethanesulphonyl)imide ([AMIM][N(SO2CF3)2])-based sol-gel fibers reported by other paper. The prepared fiber also have other advantages such as the excellent repeatability (RSD<9.4%), easy preparation and low cost.(2) The prepared [AMIM][BF4]-based sol-gel fiber was used to determining OPEs in water samples followed with GC-FPD. The experimental parameters that influenced the extraction efficiency, includingextraction time, extraction temperature, stirring rate and ionic strength, were investigated and optimized. Under the optimal conditions, the method detection limits (S/N=3) were in the range of 0.7-12 ng L-1, and the limits of quantification (S/N=10) were between 1.0 and 28 ng L-1. The repeatability of a single fiber varied from 3.3 to 7.6%(intra-day precision, n=6) and 4.3 to 8.9%(inter-day precision, n=6). The reproducibility of fiber-to-fiber (n=6) was in the range of 3.1-9.4%. The proposed method was applied successfully to the determination of OPEs in lake water, waste water, sewage treatment plant effluent and tap water with recoveries varying from 75.2 to 101.8%. The proposed method exhibits good precision, detection limit and linear response over a wide concentration range of OPEs. In addition, the proposed method shows good recoveries and RSDs of TEHP, which overcomes the disadvantage of the commercial fibers.(3) AMIM][BF4]-based sol-gel SPME fiber was applied to determining OPEs in sediment combined with GC-FPD and accelerated solvent extraction (ASE). The parameters of ASE were investigated and optimized. Under the optimal conditions, the linear range is 0.8-100 ng/g with good recoveries between 77.3-105.1%(RSD<9.8%). The proposed method was also successfully applied to the determination of OPEs in real sediments with satisfying results. Beside, the proposed method is simple, time cost, minimal organic solvent and sensitive.(4) AMIM][BF4]-based sol-gel SPME fiber was applied to the analysis of OPEs in fish tissue, combined with GC-FPD and ASE with water used as solvent. The parameters of ASE were investigated and optimized. The proposed method exhibits good linear range (0.90-5000 ng/g), low detection limit (0.010-0.208 ng/g) and good recoveries (76.1-102.8%). Beside, the proposed method is simple, minimal organic solvent and sensitive.(5) AMIM][BF4]-based sol-gel SPME fiber was also applied to assessing the bioavailability of chlorinated OPEs in sediment, combined with Tenax extraction. The result shows that there were significant (p<0.05) linear relationship between the concentrations extracted by AMIM][BF4]-based sol-gel SPME fiber and Tenax and the lipid normalized concentration of the target compounds accumulated in the earthworm. Moreover, AMIM][BF4]-based sol-gel SPME fiber can predict more accurately the bioavailability of the chlorinated OPEs in sediment than Tenax extraction. It is also simple, environmental friendly, easy preparation and low cost.