A Gas Chromatographic Microsystem for Volatile Organic Compounds: Critical Components, Chemometric Algorithms, and a Laboratory Prototype for Workplace Exposure Monitoring.

micro-gas chromatography;exposure assessment;industrial hygiene;Public Health;Health Sciences;Environmental Health Sciences

Bryant-Genevier, JonathanXi, Chuanwu ;

University of Michigan

关键词: micro-gas chromatography;    exposure assessment;    industrial hygiene;    Public Health;    Health Sciences;    Environmental Health Sciences;   

Others  :  https://deepblue.lib.umich.edu/bitstream/handle/2027.42/133310/genevier_1.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Current methods for evaluating worker exposures to mixtures of airborne volatile organic compounds (VOC) entail the collection of breathing-zone air samples, typically over several hours, followed by off-site laboratory analysis.Performing measurements with a direct-reading instrument worn by the worker would improve the quality of exposure data by capturing exposure dynamics within a shift. This dissertation describes work directed toward the development of a wearable, battery-powered instrument containing a gas chromatographic microsystem (mGC) made from Si-microfabricated components, which offers the potential for quantitative determinations of multiple VOCs. The core components of our μGC are a dual-adsorbent micro-preconcentrator-focuser (μPCF), a dual-μcolumn separation module, and a μsensor-array detector. The latter consists of 4-8 chemiresistors (CR) coated with monolayer-protected Au nanoparticles (MPN), which collectively yield partially selective response patterns that enhance the recognition/discrimination of VOCs. In phase one of this research we adapted a multivariate curve resolution method to the problem of differentiating and quantifying the components of chromatographically unresolved VOCs on the basis of their CR-array response patterns. Results showed that the rank of a given composite peak could be correctly determined in most cases, but, due to the low dimensionality of the array, the accuracies of recognition and quantification were less than optimal in most cases. Next, we optimized the mPCF for the capture and injection of VOCs within a specified vapor pressure range at concentrations near their respective occupational exposure limits.Using a few mg each of two high-surface-area graphitized carbons, conditions were established to permit exhaustive selective trapping of VOCs in sample volumes sufficient to meet required detection limits of all mixture components, and efficient, focused thermal desorption/injection to facilitate rapid, high-resolution separations of all components. Phase three entailed the design, assembly, and characterization of a first-generation laboratory prototype μGC. Component-level and system-level characterizations yielded a set of operating conditions suitable for numerous possible workplace exposure scenarios. The reproducible analysis of mixtures of VOCs at relevant concentrations was demonstrated; the combination of retention times and response patterns provided the identity and quantity of all analytes. Results have provided critical guidance for the next-generation wearable μGC.