The development of a completely micro-fabricated and autonomous vapor analysis system for environmental monitoring is currently underway at the Wireless Integrated Microsystems Engineering Research Center at the University of Michigan. Two critical initiatives in this project are the design and implementation of micro-fabricated columns with adequate resolving power to target 30-50 volatile organic compounds, and the development of a micro-plasma detector. The stationary phase deposition and subsequent performance of micro-fabricated gas chromatography columns etched in silicon substrates is described. The columns are 3.0-m long with 150-mm wide and 240-mm deep rectangular channels formed by deep reactive-ion etching. Stationary phase deposition was accomplished using both static and dynamic coating techniques. Columns were coated with both non-polar dimethyl polysiloxane and moderately polar trifluoropropylmethyl polysiloxane stationary phases. Studies of square cross-section fused silica capillary columns have been conducted to characterize stationary phase film thickness and uniformity while manipulating stationary phase solution concentration, flow rate, and residence time in the column. Evaluation of the columns was done using a spilt/splitless injector and a flame ionization detector.
The use of a micro-plasma as a vapor detector in gas chromatography is being evaluated. Micro-plasma spectroscopy offers high sensitivity and low power consumption, which make this appealing as an autonomous and portable GC detector. In addition, very high specificity can be obtained to facilitate component identification and the deconvolution of overlapping chromatographic peaks. Preliminary evaluations of sensitivity limits, response linearity, and selectivity will be described. Chromatograms from the interface of the plasma detector with micro-fabricated columns will be presented.
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