Application of Headspace Liquid-Phase Microextraction Using Ionic Liquid as Extractant Combined with Gas Chromatography-Hydrogen Flame Ionization Detector to the Determination of BTEXs in Water

This paper presents a new headspace-liquid-phase microextraction (HS-LPME) strategy for extraction and preconcentration of benzene, toluene, ethyl- benzene, and o-, m- and p-xylenes (BTEXs) from aqueous samples. A typical room temperature ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF₆), was used as extractant, and the extract was subsequently determined by gas chromatography-hydrogen flame ionization detection (GC-FID). Parameters such as ionic liquid volume, sampling temperature, extraction time, stirring rate and salt content, were found to have significant effects on the HS-LPME. The optimized experimental conditions for extraction of target compounds were: 4 ¿L of [BMIM]PF₆, 20 min extraction time, a stirring rate of 800 rpm and 40% sodium nitrate (w/v) in a sample solution at temperature of 70°C. The proposed method provided good recoveries in the range of 94.7~101.0%, and the related standard deviations (RSDs) (n=10) of 2.5~9.3%. The limits of detection (LODs) varied from 9.8 to 38.9 ¿g L^-1 (S/N = 3) using GC-FID. This novel method was applied to the analysis of BTEXs in lake water and river water.