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Immobilization of Organic Molecules within Perfluorosulfonic Acid Membranes for Optical Sensing in Humid Environments

Worrall, Adam D
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1415615234

Abstract Details

2014, PhD, University of Cincinnati, Engineering and Applied Science: Chemical Engineering.
A novel technique for the real-time detection of acetone in human breath was developed as a potential non-invasive medical diagnostic tool for use in the determination of blood glucose concentrations. Perfluorosulfonic acid polymer membranes were used as the heterogeneous catalyst for the acid condensation reaction of acetone as it diffused into the membrane and resorcinol, which was imbibed in the membrane prior to exposure. The resulting product yielded a unique colorimetric response, which could be measured over time using a UV/Vis spectrophotometer and was found to be dependent on the concentration of acetone. The colorimetric response in the membrane was calibrated to determine acetone concentrations from 0.5 ppmv to 6 ppmv over time. Solvent extraction from exposed membranes followed by mass spectroscopy was used to determine the product formed during the reaction. The response signal was significantly reduced by the presence of water vapor. This effect was hypothesized to be associated with the rapid deprotonation of the perfluorosulfonic acid groups in the presence of water resulting in loss of catalytic activity. By introducing a weak organic acid into the membrane prior to exposure, it was possible to preserve the catalytic activity of the perfluorosulfonic acid groups. The organic acid did not catalyze the reaction itself, but rather, by altering the local dielectric environment, increased the pKa of the perfluorosulfonic acid groups analogous to mixed solvent effects found in homogeneous liquid phase systems. This effect was confirmed by comparing several other similar organic acids with lower pKa values. An increase in absorbance due to the reaction was observed in the presence of 100% relative humidity as the pKa of the organic acid added was increased while maintaining a constant concentration of organic acid present in the membrane. This is the first time this mechanism has been demonstrated for heterogeneous gas-solid systems. As a result of this finding, it is now possible to detect acetone in high humidity samples such as human breath. A clinical trial was conducted to determine whether there was a correlation between acetone present in the breath of diabetic patients and their corresponding blood glucose concentration. All patients were tested at least an hour after eating with breath samples collected within moments of a blood glucometer reading. The breath samples were then processed using prepared membrane samples containing set concentrations of both resorcinol and tiglic acid. A strong correlation was observed between breath acetone concentrations and blood glucose concentrations for diabetics. This correlation opens the door for this technique to be explored as a non-invasive alternative to traditional blood glucometers.
Anastasios Angelopoulos, Ph.D. (Committee Chair)
Jonathan Bernstein, M.D. (Committee Member)
Rakesh Govind, Ph.D. (Committee Member)
Dale Schaefer, Ph.D. (Committee Member)
89 p.
Chemical Engineering
Optical Sensing; Membrane Catalysis; Breath Analysis; Acetone Detection; Perfluorosulfonic Acid Membranes

Recommended Citations

Citations

  • Worrall, A. D. (2014). Immobilization of Organic Molecules within Perfluorosulfonic Acid Membranes for Optical Sensing in Humid Environments [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1415615234

    APA Style (7th edition)

  • Worrall, Adam. Immobilization of Organic Molecules within Perfluorosulfonic Acid Membranes for Optical Sensing in Humid Environments. 2014. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1415615234.

    MLA Style (8th edition)

  • Worrall, Adam. "Immobilization of Organic Molecules within Perfluorosulfonic Acid Membranes for Optical Sensing in Humid Environments." Doctoral dissertation, University of Cincinnati, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1415615234

    Chicago Manual of Style (17th edition)

ucin1415615234
352
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This open access ETD is published by University of Cincinnati and OhioLINK.