Headspace liquid-phase microextraction of chlorobenzenes in soil with gas chromatography-electron capture detection.

The organic solvent film formed in a microsyringe barrel was used as an extraction interface in headspace liquid-phase microextraction (HS-LPME) of chlorobenzenes. Some common organic solvents with different vapor pressures (9.33-12 918.9 Pa) were studied as extractants. The results indicated that even the solvent with the highest vapor pressure (cyclohexane) can be used to carry out the extraction successfully. In general, the reasons for successful extraction are the very small space (5 mm3) within the microsyringe barrel and the fast equilibrium between gaseous analytes and organic solvent film. Both of these factors significantly reduced the risk of solvent loss during extraction. Thus, the choice of extraction solvent for the present method was very flexible. From the viewpoint of extraction efficiency, toluene (which has relatively low vapor pressure) was found to provide the best extraction efficiency. The effects of sampling volume, organic solvent volume, syringe withdrawal rate, and number of extraction cycles were also investigated. The procedure with respect to repeatability and limits of detection was evaluated by soil spiked with chlorobenzenes. Repeatabilitywas between 5.7 and 17.7%, and the limits of detection were 6-14 ng/g. HS-LPME was shown to be an inexpensive, fast, and simple sample preparation method for volatile compounds.