The Premier Conference & Expo for Occupational & Environmental Health & Safety Professionals AIHce 2011

1 Multi-Stage Preconcentrator/Focuser Module Designed to Enable Trace Level Determinations of Trichloroethylene in Indoor Air with a Microfabricated Gas Chromatograph T. Sukaew, E.T. Zellers, H. Chang, G. Serrano, University of Michigan, Ann Arbor, MI. Vapor intrusion of trichloroethylene (TCE) vapors into homes and workplaces from surrounding TCE-contaminated soil is a pervasive problem throughout the U.S. This project concerns the development and characterization of a multistage preconcentrator-focuser module (PCF) to be integrated into a prototype microfabricated gas chromatograph (μGC) being developed for in situ determinations of TCE in indoor environments at risk for vapor intrusion. The goals of the study were to determine the optimal adsorbent materials and operating conditions required for selective, quantitative capture/transfer of TCE to a downstream GC column. The PCF consists of three adsorbent-packed devices arranged in series: a pre-trap of conventional (tubular metal) design for capturing high boiling interferences; a high-volume sampler designed for selectively capturing TCE; and a microfabricated focuser (F) for focusing and injecting samples. the adsorbent masses, sampling and desorption flow rates, and heating profiles required to achieve the goals were determined in the lab on each device individually and then on the assembled PCF module using static test atmospheres of the contaminant vapors and a conventional GC column and FID or ECD detector. A 50-mg pre-trap bed of the graphitized carbon Carbopack B efficiently trapped interferences with vapor pressures < 3 torr, while not retaining TCE. A 100-mg sampler bed of the graphitized carbon Carbopack X quantitatively captured TCE in the presence of 25 interferences in sample volumes of ≤ 30 L. A 2.2-mg F bed quantitatively captured TCE thermally desorbed from the sampler and provided a sharp injection plug to the downstream column upon rapid thermal desorption. An average TCE transfer efficiency of 107% was achieved for a 20-L sample containing 0.2 ppb of TCE and 27 relevant co-contaminants, with a preconcentration factor of ~800,000. The PCF provides performance adequate for detecting TCE vapor intrusion with a GC.