Development of a hollow waveguide sampler for detection of chlorinated aromatic compounds in soils

In this paper, a Fourier transform infrared (FT-IR) spectroscopic method for detection of chlorinated aromatic compounds in soils was developed. The sensing device of this method was based on an infrared hollow waveguide, the inner surface of which was coated with a hydrophobic film. Vaporized chlorinated aromatic compounds from soils were trapped onto the hydrophobic film of the hollow waveguide sampler following detection by FT-IR spectrometry. The extraction process in this method was similar to the headspace solid-phase microextraction (HSSPME) in principle. Means of increasing the speed of transfer of the vaporized organic species to the sampler were also studied. Results indicated that, with a negative pressure on the end of the sampler, the speed of transfer increased significantly. Vapor pressures of the analytes were used as an indication to test the limitation of this method in the analysis of organic compounds in soils. Results showed that analytes with vapor pressures lower than 12 Torr could be detected quantitatively. The typical R-square of the regression on the concentration and IR signals was around 0.99 and the typical detection limits were in the range of hundreds of parts per billion.