Development of the headspace SPME/ATR-IR method for detection of chlorinated aromatic compounds in soils

摘要

In this paper, a new method based on attenuated total reflection infrared (ATR-IR) spectroscopy was developed to detect chlorinated aromatic compounds in soil. To eliminate the problems associated in inspection of soil samples by the ATR-IR method, chlorinated compounds were evaporated from soil matrices and detected in the headspace. The sensing device was constructed by an internal reflection element (IRE) coated with a hydrophobic film to attract and concentrate chlorinated compounds evaporated to the headspace. Factors that influence the analytical signals were studied such as the moisture content, volatilities of analytes, and effect of heating temperature. Results indicated that the addition of thermal energy to the soil sample resulted in an increase of IR signal. However, the IRE was also warmed up and caused a slight decrease of the IR signals after a long detection time. The studies of the influence of moisture indicated that a small amount of water present in soils could tremendously increase the intensity of detected IR signals. The further increase of moisture contents resulted in a decrease of the analytical signals, and the optimal signal was found when soil samples contained 5% (v/w) water. Results in analyses of compounds with different volatilities indicated that even with vapor pressure lower than 0.017 Torrs, quality IR spectra could still be obtained. Using the optimal conditions found in this work, the results in determination of five compounds in soil samples indicated that the linear regression coefficients (R-square) were higher than 0.992 with detection limits around a few hundreds of ppb.