Microfabricated Gas Chromatograph for On-Site Determinations of TCE in Indoor Air Arising from Vapor Intrusion. 2. Spatial/Temporal Monitoring

Abstract

We demonstrate the use of two prototype Si-microfabricated gas chromatographs (μGC) for continuous, short-term measurements of indoor trichloroethylene (TCE) vapor concentrations related to the investigation of TCE vapor intrusion (VI) in two houses. In the first house, with documented TCE VI, temporal variations in TCE air concentrations were monitored continuously for up to 48 h near the primary VI entry location under different levels of induced differential pressure (relative to the subslab). Concentrations ranged from 0.23 to 27 ppb by volume (1.2-150 μg/m(3)), and concentration trends agreed closely with those determined from concurrent reference samples. The sensitivity and temporal resolution of the measurements were sufficiently high to detect transient fluctuations in concentration resulting from short-term changes in variables affecting the extent of VI. Spatial monitoring showed a decreasing TCE concentration gradient with increasing distance from the primary VI entry location. In the second house, with no TCE VI, spatial profiles derived from the μGC prototype data revealed an intentionally hidden source of TCE within a closet, demonstrating the capability for locating non-VI sources. Concentrations measured in this house ranged from 0.51 to 56 ppb (2.7-300 μg/m(3)), in good agreement with reference method values. This first field demonstration of μGC technology for automated, near-real-time, selective VOC monitoring at low- or subppb levels augurs well for its use in short- and long-term on-site analysis of indoor air in support of VI assessments.

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

“…With slight modifications, it appears feasible to extend the use of this instrumentation to the simultaneous analysis of other VOCs. The companion article that follows (Part 2) 27 demonstrates the use of these prototype μGCs for monitoring spatial and temporal variations in TCE concentrations. …”

Review of Portable and Low-Cost Sensors for the Ambient Air Monitoring of Benzene and Other Volatile Organic Compounds

“…The application of the μGC was demonstrated through laboratory testing. The prototype was then implemented in real case studies of indoor air analysis including validation against reference measurements [ 143 , 144 ] showing low bias (generally within ±25%), linearity of the μGC in the range between 4.8 and 77 ppb and a re-evaluated LOD of 52 ppt. A subsequent publication by Bryant-Genevier et al [ 145 ] was aimed at improving and applying chemometric methods for use with micro-GC chemiresistor sensor arrays.…”

Through the years with on-a-chip gas chromatography: a review

“…Early applications of such chip-based GC systems were only reported in analyses of hydrocarbons 3 and gas samples. 80 However, as shown in Table 2, the development of these systems has been extended across a wide variety of application areas such as health service, 45,51,57,81,111,134,139,140 industry pollution monitoring, 56,57,111 environmental analysis, 32,54,56,57,82,88,111,134,141 homeland security, 50,142,143 petrochemical industries, 143 and as the second dimension of comprehensive two-dimensional gas chromatography (GC × GC). 80,97,98,111,137 Nowadays chipbased gas chromatograph instruments are commercially available from companies such as Dolomite, 144 C2V 145 , etc.…”