Skip to Main Content
 

Global Search Box

 
 
 
 

Files

File List


21124.pdf (4.49 MB)

ETD Abstract Container

Abstract Header

The Impact of Humidity on an Optical Chemical Sensing Device for Non-invasive Exhaled Gas Monitoring

Qian, Zexin
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1471347710

Abstract Details

2016, MS, University of Cincinnati, Engineering and Applied Science: Chemical Engineering.
A novel technique for the detection of acetone in human breath was previously developed as a non-invasive medical diagnostic tool for potential use in the monitoring blood glucose level of diabetic patients. Perfluorosulfonic acid (PSA) polymer membrane, commercially available as Nafion® 117, was used as the heterogeneous catalyst for the condensation reaction of ambient acetone and imbibed immobilized resorcinol reagent. The condensation reaction product, a flavan compound, yielded a unique colorimetric response, which can be measured over time using UV/VIS spectroscopy. Previous studies have shown that by introducing a weak organic acid such as tiglic acid into the membrane prior to exposure, it is possible to preserve the catalytic activity of the PSA groups. An increase in light absorbance due to the reaction was observed in the presence of 100% relative humidity as the concentration of the tiglic acid imbibed increased. This was the first time this colorimetric response was shown to provide comparable light absorption under both ambient humidity and 100% relative humidity condition. The focus of the research described this thesis was to develop an optical sensing device for real time detection in practical clinical applications. An in-situ flow cell was used in this work to determine whether the condensation reaction was able to provide a rapid response during acetone exposure. Using the flow cell system, dynamic response of different concentration of tiglic acid imbibed membrane exposure to both ambient humidity and 100% relative humidity was determined. The dynamic response obtained in this research confirmed that acid based membrane was able to provide us a signal within 100 seconds under both dry and wet condition. The results suggested that the acid based membrane can be used in uncontrollable humidity environment such as human breath but only in the kinetic-controlled region of acetone transport into the membrane. As part of this work, evaluation and optimization of a bench-top prototype was conducted to evaluate the effects of temperature, flow rate and pre and post humidification of both membrane and sample chamber. A strong linear correlation of the optical signal from the device was observed at a given exposure to acetone at early times as long as steady humidification in the sample chamber was maintained. Steady humidification was inferred from the strong influence of flow rate (which affected pressure), temperature, and sample chamber pre-conditioning. A small group of clinical trials were conducted assess the prototype response under real-world conditions. As in the case of constant acetone exposure, linear correlation (typically, R2>0.9) was observed between the optical response and exposure at early times. Consistent with previous work that suggested correlation of breath acetone and blood glucose, we observed a linear correlation between the slope of the optical response and breath acetone concentrations and blood glucose concentrations for diabetics. Such excellent correlations motivate further research on uses of this device to assess the exhaled breath composition for various disease biomarkers.
Anastasios Angelopoulos, Ph.D. (Committee Chair)
Jonathan Bernstein, M.D. (Committee Member)
Rakesh Govind, Ph.D. (Committee Member)
68 p.
Chemical Engineering
sensor; Nafion; acetone; acid based equilibria

Recommended Citations

Citations

  • Qian, Z. (2016). The Impact of Humidity on an Optical Chemical Sensing Device for Non-invasive Exhaled Gas Monitoring [Master's thesis, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1471347710

    APA Style (7th edition)

  • Qian, Zexin. The Impact of Humidity on an Optical Chemical Sensing Device for Non-invasive Exhaled Gas Monitoring. 2016. University of Cincinnati, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1471347710.

    MLA Style (8th edition)

  • Qian, Zexin. "The Impact of Humidity on an Optical Chemical Sensing Device for Non-invasive Exhaled Gas Monitoring." Master's thesis, University of Cincinnati, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1471347710

    Chicago Manual of Style (17th edition)

ucin1471347710
387
© 2016, all rights reserved.
This open access ETD is published by University of Cincinnati and OhioLINK.