The broad goal of this project is to develop and characterize a wearable gas chromatographic microanalytical system (mGC) for near-real-time recognition and quantification of the components of complex mixtures of volatile organic compounds (VOC) encountered in working environments. The proposed mGC, referred to as a Personal Exposure Monitoring Microsystem (PEMM), will be battery operated, autonomous, and small/light-weight enough to mount on the belt of a worker, yet capable of simultaneous personal exposure measurements of at least 10-15 user-selectable VOCs every 10-15 minutes in a complex matrix of background VOCs. The performance of the PEMM mGC will rely on an ensemble of Si-microfabricated devices for selective sampling/preconcentration;focused injection;temperature-programmed, dual-column chromatographic separation;and 'spectral detection'with a microsensor array. These will be combined with a commercial mini-pump, possibly a small on-board He gas supply, mini-valves, interface circuitry, an embedded microcontroller for operating the instrument and storing exposure data, and a wireless link for on-the-fly downloading of data to a smartphone or remote host computer. Post-shift analysis of the chromatographically resolved array response patterns for each mixture component will permit construction of detailed time-exposure profiles for comparison with occupational exposure limits or classification of exposure frequencies and intensities for epidemiologic studies. Innovative designs and strategies for selective preconcentration, high-resolution/high-speed separation, and microsensor-based detection with chemometric peak deconvolution will be implemented in the PEMM, and operating conditions will be adjustable to permit accurate measurements of VOC concentrations over a ~50-fold range for any compound, spanning from 0.1-5 times the recommended exposure limits. Detection limits as low as 0.05 ppm will be achievable. The capability of this instrument for assessing human exposures to VOCs will be demonstrated through a series of mock-field tests using target and background VOC mixtures of varying complexity in task-exposure scenarios representative of jobs in NORA-defined construction, manufacturing, health care, and other sectors. The successful project will yield a tool with unprecedented capabilities for measuring worker exposures to VOCs, in terms of temporal resolution, the number of specific analytes, and the cost per measurement. This will address stated needs/goals primarily in NIOSH cross-sector programs in Exposure Assessment and Emergency Preparedness and Response. By including a start-up company on our team with expressed interest in commercializing this technology, we will facilitate its transfer to the private sector (and user community), consistent with NIOSHs Research-to-Practice initiative.
The lack of adequate exposure data has been consistently cited as the most critical factor limiting efforts to define exposure-response relationships in epidemiologic studies of disease in worker populations, particularly where complex mixtures are involved. This, in turn, impedes efforts to establish meaningful workplace exposure limits and to determine compliance with such limits once established. The successful project will fill the need for small, inexpensive, wearable, turn-key instrumentation capable of direct, autonomous identification and quantification of multiple user-selectable VOCs in complex workplace-air mixtures with high temporal resolution.
|Bryant-Genevier, Jonathan; Zellers, Edward T (2015) Toward a microfabricated preconcentrator-focuser for a wearable micro-scale gas chromatograph. J Chromatogr A 1422:299-309|