Feasibility of Determining Workplace Microbial VOCs with a Microfabricated

Research Trainee: Hung-Wei Chang, PhD, Postdoctoral Fellow, Dept. of Environmental Health Sciences at the University of Michigan

Faculty Researcher: Chuanwu Xi, PhD, Assistant Professor of Environmental Health Sciences at the University of Michigan

This proposal seeks pilot funding to adapt a high-performance prototype microfabricated gas chromatograph (μGC) to the determination of microbial volatile organic compounds (MVOC) emitted by pathogenic and non-pathogenic bacteria and fungi relevant to occupational health. Potential applications include monitoring exposures at agricultural and forestry worksites, wastewater treatment facilities, composting facilities, and water-infiltrated office buildings for the presence and viability of bacteria and fungi. Although resurgent interest in MVOC monitoring is evident from the literature, current approaches rely on large, expensive instruments that are not suitable for untrained persons or on so-called ‘electronic noses’ (i.e., stand alone multi-sensor arrays) that can serve as comparators but do not provide quantitative analysis. The research proposed here will explore the feasibility of monitoring collections of microbial VOCs that are characteristic of certain strains of bacteria and fungi, so-called ‘signature MVOCs’, and to determine if they can be detected at occupationally relevant concentrations in actual samples. The project will serve to initiate a collaboration between two groups in the EHS Department at Michigan, will be led by a post-doctoral researcher with no prior experience in occupational health, and will address sector priorities set forth in the most recent (12/08) NORA agenda in agriculture, forestry, and fishing where microbial contamination is often encountered and the need for better surveillance methods is recognized. Initial results will be used to support proposals to other organizations for follow-on funding. Having a portable (wearable), turn-key instrument capable of identifying and quantifying microbially generated air contaminants would provide a means of screening individual exposures at low cost in a matter of minutes in field settings. The prototype to be adapted in this project has been named SPIRON, and it is one of several μGC prototypes under development in the Center for Wireless Integrated Microsystems (WIMS). It is about the size of a calculator and incorporates state-of-the-art features, including a multi-stage preconcentrator, series-coupled separation columns with independent temperature programmed retention, and a detector comprising an integrated array of chemiresistor (CR) microsensors that provides a digital “spectrum” of eluting vapors. Capture, separation, and detection/identification of as many as 50 MVOCs (and/or interferences) in a single analysis is anticipated and limits of detection in the parts-per-trillion concentration range are expected based on data collected from previous prototypes and with meso-scale analogues of the SPIRON prototype.

This 6-month project will determine the feasibility of applying this technology to the challenging problem of identifying and quantifying MVOCs from contaminated workplace air. This will be accomplished by developing materials and operating conditions related to sampling, preconcentration, separation, and detection suitable for the capture and speciation of MVOCs above cultured microbe populations to achieve desired detection limits, while also rejecting or compensating for high background humidity and potentially interfering VOCs.

 

Research trainee’s current position:
Hung-Wei Chang is currently an Assistant Professor of Chemistry at Fu Jen Catholic University in Taiwan.