Abstract
On-line Fourier transform infrared (FT-IR) spectroscopy was applied to monitor the concentration of halogenated volatile organic compounds in a sample-preparation process that simulates long-term, slow accumulation of contaminants in soils (i.e., aging). Artificial aging is conducted by circulating a supercritical fluid solution containing the contaminant(s) of interest through a packed soil column. Mid-infrared spectra of several volatile halocarbons were measured in supercritical Xe and CO<sub>2</sub> to evaluate possible interferences from the strong absorption of CO<sub>2</sub>. Although some of the C–X bands were partially masked in supercritical CO<sub>2</sub>, all of the compounds studied had distinct spectral features in the region 1400–700 cm<sup>−1</sup> and could be monitored in either solvent. Quantitative measurements of halogenated volatile organics in supercritical CO<sub>2</sub> were demonstrated with CCl<sub>4</sub>. Excellent results were obtained over the range 7–280 mM. Representative artificial aging experiments were conducted on two test soils using CCl<sub>4</sub> as the contaminant. On-line (FT-IR) estimates of the aged soil concentrations were 1.3–4.4 times higher than off-line concentrations obtained by gas chromatography/mass spectrometry. The discrepancies were primarily ascribed to post-aging losses that occurred during depressurization and subsequent sample handling. FT-IR spectroscopy is shown to be a powerful tool for monitoring soil loading behavior and for developing artificial aging protocols.
PDF Article
More Like This
Cited By
You do not have subscription access to this journal. Cited by links are available to subscribers only. You may subscribe either as an Optica member, or as an authorized user of your institution.
Contact your librarian or system administrator
or
Login to access Optica Member Subscription
Add to BibSonomy