Apr 20th, 1:00 PM - 4:00 PM
Calibration and Field Sample Collection Using an Ion Mobility Spectrometer for Detection and Analysis of Subsurface Volatile Organic Compounds
Dr. Molly Gribb
An ion mobility spectrometer (IMS) is capable of detecting gaseous volatile organic compounds (VOCs) from a chemically composite environment. An IMS system measures the drift time of ions traveling against a counter-flowing neutral drift gas within an electric field and at ambient pressure. IMS has been successfully implemented in airports and government projects for real-time detection of drugs, explosives, and chemical warfare agents. The focus of our research isto apply ion mobility spectrometry to identifying and quantifying harmful VOCs that contaminate subsurface soils. An IMS probe system designed for real-time, subsurface soil-gas sampling applications is presented. The system is encased in a 51-mm outside diameter stainless steel probe housing which includes a compact IMS sensor (at the heart of the probe), a sampling module, a signal amplifier, and high voltage system to sustain IMS performance. A heated gas chromatog raphy (GC) column has been added to the IMS system for additional separation of compounds during the extraction of complex samples. To ensure accurate VOC detection and quantification, calibration curves were created for the BTEX compounds (benzene, toluene, ethyl benzene, xylene) of known concentrations in the laboratory. These curves were used to quantify results from IMS sample spectra collected from a BTEX contaminated site. The results indicate that the IMS can be successfully used for the identification and quantification of BTEX under field conditions.