Date of Award

7-1-1996

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry

Abstract

The detection of volatile organic compounds (VOCs) in water and soil via infrared (IR) spectroscopy is difficult because the water and soil components absorb the majority of the infrared radiation. Solid phase microextraction (SPME) selectively extracts the analytes from the water and soil and allows detection in the same solid phase with no water or soil interference. Current optical methodology in SPME utilizes ultraviolet/visible, or near-infrared spectroscopy as a detection means and yields little molecular information and poor detection limits respectively. The subject of this Doctor of Philosophy (PhD) dissertation will include the development and application of SPME to Fourier transform infrared (FTIR) spectroscopy. Infrared spectroscopy is superior to ultraviolet/visible spectroscopy for the identification of molecular structure and generally has lower detection limits than near-infrared spectroscopy.The laboratory procedure shall include the design and construction of a SPME/IR cell and the development of appropriate methodology for determining VOCs in water and soil matrices. Several stationary phases commonly used in gas chromatography (e.g., poly(dimethylsiloxane), Apiezon-L) will be evaluated as a solid phase for analyte selectivity, optical transparency and feasibility for coating fiber optics. Several VOCs (e.g., benzene, toluene, chloroform and p-chlorotoluene) shall be determined in water, headspace over water and headspace over sand and soil. Measurement of the infrared signal shall be accomplished using a commercially-available FTIR and easily obtainable materials.Specific studies to be conducted include: (1) determination of the partition time, (2) analytical calibration of the technique with the VOCs extracted at equilibrium and non-equilibrium times (30 min) with the solid phase, (3) determination of the recovery of the VOCs in a real water sample as compared to a control set, and (4) adaptation of the technique to utilize fiber optics for possible remote detection of VOCs in water and soil. The results we expect to obtain from these experiments for these VOCs include partition times, linear dynamic ranges of calibration, detection limits, reproducibility of the methodology, distribution constants and useful IR bands for calibration. Finally, the potential for speciation of mixtures will be investigated by extracting the aromatic components from a water sample contaminated with gasoline.

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