Advisory Committee Chair
Advisory Committee Members
Evan L Floyd
Date of Award
Degree Name by School
Doctor of Philosophy (PhD) School of Public Health
Volatile organic compounds (VOCs) are a common source of occupational exposures. To prevent adverse health effects in employees, industrial hygienists must regularly conduct occupational air sampling to ensure exposures remain below regulatory limits. As such, the need for sensitive and reliable exposure assessment methodologies becomes apparent. Currently, diffusive sampling is popular and well-established exposure assessment method amongst professionals. However, its reliance on diffusion-driven mass uptake and chemical extraction, results in limited analytical sensitivity. In response to this, a pre-analytical technology, known as photothermal desorption (PTD), has been in development over the past decade. PTD uses pulses of high-energy light to desorb analytes from thermally conductive, carbonaceous sorbents, thereby increasing the sample mass available for instrumental analysis, compared to chemical extraction. Nevertheless, more work is needed to fully develop this emerging technique. For example, the thermal processes driving PTD have yet to be empirically investigated. Moreover, the development of a PTD-compatible sampling device is needed to make the technology ready for in-field uasage. As such, this dissertation focused on three specific aims: 1) investigate the thermal properties driving PTD; 2) design and characterize the uptake rates of a PTD-compatible diffusive sampler; and 3) quantify the analyte mass recovered via PTD, from VOCs collected by diffusive sampler prototypes. In aim 1, PTD was observed to produce temperature changes ranging between 35.2 ± 0.9 to 76 ± 4 °C iv from room temperature. Additionally, buckypaper sorbents were found to have a thermal conductivity of 10.6 ± 0.6 W/m2. During the aim 2 study, a PTD-compatible diffusive sampler was manufactured and reported to have sampling rates of 28.0 ± 2.0, 21.0 ± 1.0, 15.0 ± 1.0, and 8.5 ± 0.7 cc/min for toluene, n-hexane, trichloroethylene, and isopropyl alcohol. Finally, while investigating aim 3, the percent mass recovered of toluene, n-hexane, trichloroethylene, and isopropyl alcohol by PTD, were found to be 0.60 ± 0.09, 1.2 ± 0.09, 1.1 ± 0.1, and 14.0 ± 1.0% respectively. Overall, this early-stage data demonstrates the promising nature of PTD used with passive air samplers and provides a solid foundation for future development of this combined pre-analytical and sampling technique.
Shedd, Jacob S., "Photothermal Desorption of Volatile Organic Compounds From Buckypaper Sorbents, for Occupational Exposure Assessment" (2022). All ETDs from UAB. 333.