The development of a high-performance, hand-held microanalytical system capable of on-site identification and quantification of low-/sub-ppb concentrations of volatile organic compounds of anthropogenic and microbial origin (VOCs and MVOCs) encountered in nonindustrial indoor working environments is proposed. Advanced strategies for sample collection, component separation, and detection will be incorporated into a fieldable instrument about the size of a notebook computer. It will employ a thermally modulated dual-bed mini preconcentrator for vapor collection, a tunable, high-speed separation module, and an integrated array of micromachined flexural-plate-wave (FPW) sensors for vapor recognition and quantification. The preconcentrator will partition captured vapors onto two separate porous-polymer adsorbent beds in series, according to vapor pressure and affinity for the adsorbent, and then thermally desorb them sequentially in sharp, discrete pulses. A series of two short, high-resolution micro capillary columns, each coated with a different stationary phase, will be used for separating mixture components. The column temperature will be rapidly adjusted for each preconcentrated fraction. A pressure modulation valve at the juncture of the two columns will permit preprogramed """"""""tuning"""""""" of retention and separation, with a complete multi-component mixture separation performed in <60 sec for each preconcentrated fraction. An integrated array of six partially selected polymer-coated FPW sensors will provide multi-channel detection capabilities. Artificial neural networks will be used to identify and discriminate among vapors from their response patterns and retention times. Concentration-time analytical profiles for mixtures of up to 30 VOCs will be obtainable at measurement intervals as short as 7-10 min and stored in an embedded computer for subsequent data extraction and archiving. Physicochemical and statistical models of preconcentration, separation, and sensor responses will be used to optimize system operating parameters and to predict performance for any potential exposure scenario. Laboratory testing will demonstrate the capability for continuous measurement of complex vapor mixtures. The analytical power and versatility embodied in this system represent a significant advancement over the current state-of-the-art in vapor monitoring instruments. Dramatic reductions in the time cost of analyses of indoor VOCs and MVOCs will be realized, obviating the need for conventional sorbent-tube/GC-MS sampling and analysis for routine monitoring. This, in turn, will facilitate the assessment of exposure distributions and the implementation of rational intervention strategies to address indoor environmental quality problems.
|Zhong, Qiongyan; Steinecker, William H; Zellers, Edward T (2009) Characterization of a high-performance portable GC with a chemiresistor array detector. Analyst 134:283-93|