Microfabricated gas chromatograph for Sub-ppb determinations of TCE in vapor intrusion investigations

Abstract

A microfabricated gas chromatograph (μGC) is described and its application to the analysis of sub-parts-per-billion (ppb) concentrations of trichloroethylene (TCE) in mixtures, relevant to the problem of TCE vapor intrusion (VI) into homes and offices, is demonstrated. The system employs a MEMS focuser, dual MEMS separation columns, and MEMS interconnects along with a microsensor array. These are interfaced to a (non-MEMS) front-end pre-trap and high-volume sampler module to reduce analysis time. The response patterns generated from the sensor array for each vapor are combined with the chromatographic retention time to identify and differentiate the components of VOC mixtures. All functions are controlled by a LabView routine written in house. A chemometric method based on multivariate curve resolution has also been developed for analyzing partially resolved mixture components. First results are presented of the capture, separation, recognition, and quantification of TCE in a mixture. TCE is measured at 0.185 ppb, with a projected detection limit of 0.030 ppb (20-L sample).