A Novel Multi-Vapor Analyzer: Characterization and Application to Analyzing Breath Biomarkers of Lung Cancer
Qiongyan is the second of two speakers for the WIMS seminar.
The characterization of a novel portable multi-vapor analyzer is described and preliminary results obtained in adapting it for determinations of breath biomarkers of lung cancer. This analyzer incorporates a multi-stage adsorbent preconcentrator/focuser, series-coupled columns with independent “at-column” temperature programming and pressure tuning, and a detector comprising an array of microfabricated nanoparticle-coated chemiresistor sensors, whose response patterns can be used with retention times to identify eluting vapors. It uses scrubbed ambient air as carrier gas. Tradeoffs in system performance have been characterized. Thermal injection of preconcentrated vapors results in significant broadening of the injection band for less-volatile compounds. However, by splitting the injection stream, this factor can be mitigated. In exploring the effects of fluidic and thermal variables on detector performance, we found an approximately exponential increase in sensitivity with decreasing flow rate through the sensor cell. Increasing the sensor temperature resulted in increased peak resolution, but with decreased sensitivity. A 31-VOC mixture was separated in 7 min with only 4 binary coelutions, which could be resolved by their sensor response patterns. Seven breath biomarkers of lung cancer were separated from 30 common breath constituents in 4 min with only one binary biomarker co-elution, and with projected LODs in the ppt range for a 1-L sample.
Qiongyan Zhong (Judy) is a Ph.D. candidate in the Industrial Hygiene Program within the Department of Environmental Health Sciences at the University of Michigan, having earned an M.S. degree in Environmental Chemistry and a B.S. degree in Applied Chemistry, both from Zhongshan University in China. She began the program and joined Dr. Edward T. Zellers’ group in 2002. Her major research interest is the development of a portable air monitoring instrumentation. She has also been involved in the development of the WIMS micro-GC, with specific efforts in evaluating adsorbent materials for the micro-preconcentrator/focuser used in the system.