Development of molecularly imprinted sol-gel SPME devices for the determination of polybrominated diphenyl ethers

Abstract

Polybrominated diphenyl ethers (PBDEs) are undoubtedly one of the most important groups of organohalogenated compounds that capture the attention of environmental scientists in recent years. PBDEs are widely used as flame retardant additives in polymers and textiles and are present in nearly all of our daily appliances. There are growing evidences that these brominated flame retardants are entering the global ecosystem at a significant rate. In order to assess their risks to the environment and public health, their levels in the various environmental compartments have to be closely monitored. This, in turn, relies on the development of reliable, rapid and sensitive analytical techniques for the quantification of polybrominated organic compounds. Solid-phase microextraction (SPME) is one of the advanced sampling and sample preparation techniques that are useful in the determination of trace organics in environmental samples. Numerous studies have already reported on the use of SPME for PBDE determination in water and solid samples. The applicability of most of the commercially available SPME stationary phases in the direct sampling of PBDEs from aqueous media have been examined. They were shown to have rather poor analyte affinity and repeatability, especially towards heavier BDE congeners. There is a call for the development of new and more robust SPME coatings that possess selective affinity for BDE congeners. In this context, the feasibility of using molecularly imprinted sol-gel organically modified silicate (ORMOSIL) films as SPME stationary phases has been explored. A series of ORMOSIL films of various compositions were fabricated and examined for their stability under the SPME sampling and GC desorption conditions. The ORMOSIL coating fabricated from phenyltrimethoxysilane and tetraethoxysilane (TEOS) was found to be the most suitable candidate. Molecular imprinting of BDE-209, the heaviest PBDE congener, into the ORMOSIL-SPME coating can be easily accomplished by dissolving the congener into the sol prior to gelation. The resulting ORMOSIL-SPME coating is found to possess much higher stability and affinity towards a wide spectrum of BDE congeners with different degree of bromination. In this thesis, the detail fabrication procedure for the molecularly imprinted ORMOSIL-SPME stationary phase is described and its performance in the determination of BDE-209 and other lighter BDE congeners in municipal sewage were evaluated. Levels of dissolved total PBDE (summation of 8 BDE congeners including BDE-15, 28, 47, 100, 153, 154, 183, and 209) in the sewage influent samples obtained from various sewage treatment works (STWs) in the Pearl River Delta (PRD) region were determined to range from 13.4 pg/mL (Shatin STW) to 103 pg/mL (Tai Po STW) in Hong Kong; and 39.2 pg/mL (Guangzhou STW) to 123 pg/mL (Shenzhen Nanshan STW) in southern China (Guangdong Province). Levels of dissolved total PBDE in the effluents from these STWs were found to range from 9.78 pg/mL (Shatin STW) to 54.6 pg/mL (Wan Chai East Sewage Screening Plant) in Hong Kong; and 24.8 pg/mL in southern China (Guangzhou STW).

Date of Award	15 Jul 2008
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Hon Wah Michael LAM (Supervisor)