Microfabricated Gas Chromatograph for the Selective Determination of Trichloroethylene Vapor at Sub-Parts-Per-Billion Concentrations in Complex Mixtures

Abstract

A complete field-deployable microfabricated gas chromatograph (μGC) is described, and its adaptation to the analysis of low- and subparts-per-billion (ppb) concentrations of trichloroethylene (TCE) vapors in complex mixtures is demonstrated through laboratory testing. The specific application being addressed concerns the problem of indoor air contamination by TCE vapor intrusion. The μGC prototype employs a microfabricated focuser, dual microfabricated separation columns, and a microsensor array. These are interfaced to a nonmicrofabricated front-end pretrap and high-volume sampler module to reduce analysis time and limits of detection (LOD). Selective preconcentration and focusing are coupled with rapid chromatographic separation and multisensor detection for the determination of TCE in the presence of up to 45 interferences. Autonomous operation is possible via a laptop computer. Preconcentration factors as high as 500 000 are achieved. Sensitivities are constant over the range of captured TCE masses tested (i.e., 9-390 ng), and TCE is measured in a test atmosphere at 120 parts-per-trillion (ppt), with a projected LOD of 40 ppt (4.2 ng captured, 20 L sample) and a maximum sampling + analytical cycle time of 36 min. Short- and medium-term (1 month) variations in retention time, absolute responses, and response patterns are within acceptable limits.

Microfabricated Gas Chromatograph for On-Site Determination of Trichloroethylene in Indoor Air Arising from Vapor Intrusion. 1. Field Evaluation

“…The rationale for the system design, as well as details of the fabrication methods and structures of the microscale components, front-end preconcentration module, and supporting hardware and software, have been presented elsewhere. 26,31 There are four operating modes: sampling, focusing, stabilization, and analysis. In sampling mode, an air sample is drawn at ∼0.78 L/min through the pretrap and sampler with the sample pump ( Figure 1a).…”

Ethylene detection in fruit supply chains

“…Several attempts have been reported since 1979 (e.g. [37]). One of the latest developments is presented in Sun et al [38].…”

Characterization of a micro-helium discharge detector for gas chromatography

“…Such analyses are highly applicable for homeland security, space exploration, on-site or distributed environmental monitoring mechanisms, food assessment, etc. [1][2][3][4][5][6][7][8][9][10][11][12][13]. In a typical GC system, the sample mixture is first collected on an adsorbent bed referred to as the pre-concentrator.…”