Abstract
The analysis of toxic volatile organic compounds (VOCs) in environmental air is important because toxic VOCs induce adverse effects on human health. Although gas chromatography- mass spectrometry (GC-MS) is the standard instrument for analysis of trace VOCs in air, this mode of analysis requires preconcentration and cryogenic processes. The preconcentration and subsequent thermal desorption of VOCs require special instruments and a long time of processing sample that significantly limit applications of GC-MS for monitoring indoor and outdoor VOC levels. Using a microfabricated preconcentrator for VOC analysis also has the challenge of a large sample volume for concentration. Using solid-phase microextraction (SPME) for VOC analysis by GC-MS often approaches the limit of detection of the GC-MS instrument for trace VOCs in air. This work reports a simple method to integrate microfabricated preconcentrators with commercial SPME fibers in a two-stage concentration processes to achieve rapid and reliable measurement of trace VOCs in air by GC-MS. We designed and fabricated a preconcentrator with micropillars in a microfluidic chamber to support sorbents and to increase the heat transfer rate to the sorbents for rapid thermal desorption. The effects of air flow rates through the preconcentrator on VOCs adsorption and thermal desorption were optimized for increasing analytical accuracy of VOCs measurements. The integration of a micropreconcentrator with SPME enabled measurements of sub-ppb levels of benzene, toluene, ethylbenzene, and xylene (BTEX), and trichloroethylene (TCE) in environmental air by GC-MS.