Synthesis And Characterization Of [BMIM]PF₆ And It's Applications In Analysis Of BTEXs In Water

Benzene,toluene,ethyl benzene and xylenes(BTEXs) have aroused increasing interest for its hazards on both human health and the environment. A serious problem encountered in the determination of BTEXs is that the BTEXs usually presents in water at a very low concentration, resulting poor analytical accuracy and precision. Therefore, it is of great importance to develop very sensitive and reliable preconcentration/separation procedures prior to the instrumental determination.Room temperature ionic liquids (ILs) have a number of excellent properties, such as a good chemical and thermal stability, a very low vapor pressure as well as a good solving ability for numerous compounds. ILs are now universally accepted and used as a new type of green solvents.In this work, two new methods for analysis of trace BTEXs in water samples were developed, based on the combination of liquid-phase microextraction (LPME), using 1-Butyl-3-methy-limidazolium hexafluorophosphate ([BMIM]PF₆) as the extractant, and determination by gas chromatography. The followings are the experimental results obtained:1. 1-Butyl-3-methylimidazolium biomide ([BMIM]Br) was microwave -assisted synthesized within 3 min, and then [BMIM]PF₆ was prepared through double decomposition reactions using [BMIM]Br. The products were characterized by ultraviolet-visible spectrum and infrared spectrum.2. [BMIM]PF₆ was used for headspace liquid-phase microextraction (HS-LPME) of BTEXs . BTEXs are conveniently and rapidly extracted from water into a 4μL drop of [BMIM]PF6 suspended at the tip of a microsyringe, followed by gas chromatographic determination. Various parameters were investigated in detail, including drop volume, temperature, stirring time and salt effect. The recovery were found to be 94.7%-101.0% with RSD(n=10) of 1.9%-9.3%, and detection limits were in the range of 7.18μg/L-38.48μg/L.3. [BMIM]PF₆ was also used for hollow fiber liquid-phase microextraction (HF-LPME) of BTEXs . BTEXs were extracted by 8μL of [BMIM]PF₆ set in a hollow fiber followed by gas chromatographic determination. Various parameters were investigated in detail, including drop volume, temperature, stirring time, stirring rate and salt effect. The recovery were found to be 93.6 % - 101.0 % with RSD(n= 10) of 1.3%- 11.4%, and detection limits were in the range of 4.44μg/L--7.51μg/L.4. The proposed methods were applied to the determination of trace BTEXs in onelake water sample and two Zhujiang river water samples with satisfactory results.