Headspace liquid-phase microextraction of trihalomethanes in drinking water and their gas chromatographic determination

摘要

In the present work, a novel method for the determination of trihalomethanes (THMs) such as chloroform, dichlorobromomethane, chlorodibromomethane and bromoform in drinking water has been described. It is based on coupling headspace liquid-phase microextraction (HS-LPME) with gas chromatography-electron capture detector (GC-ECD). A microdrop of organic solvent at the tip of a commercial microsyringe was used to extract analytes from aqueous samples. Three organic solvents-xylene, ethylene glycol and 1-octanol-were compared and 1-octanol was the most sensitive solvent for the analytes. Extraction conditions such as headspace volume, extraction time, stirring rate, content of NaCl and extraction temperature were found to have significant influence on extraction efficiency. The optimized conditions were 15 ml headspace volume in a 40 ml vial, 10 min extraction time and 800 rpm stirring rate at 20 ℃ with 0.3 g ml~(-1) NaCl. The linear range was 1–100 μg l~(-1) for THMs. The limits of detection (LODs) ranged from 0.15 μg l~(-1) (for dichlorobromomethane and chlorodibromomethane) to 0.4 μg l~(-1) (for chloroform); and relative standard deviations (RSD) for most of THMs at the 10 μg l~(-1) level were below 10%. Real samples collected from tap water and well water were successfully analyzed using the proposed method. The recovery of spiked water samples was from 101 to 112%.