Preparation, Evaluation, and Application of Silicon/Glass Micro-fabricated Gas Chromatography Columns for the Analysis of Volatile Organic Compounds
Gordon R. Lambertus,
Graduate Student (UM)
ABSTRACT: The development of field-portable and micro-fabricated instrumentation is of material importance for real-time autonomous sensing in environmental, industrial, and homeland security applications. A micro-fabricated gas chromatograph ( µGC), intended for use in the analysis of complex mixtures of volatile organic compounds (VOCs) in atmospheric air samples is being developed at the Wireless Integrated MicroSystems Engineering Research Center (WIMS-ERC) at the University of Michigan. A critical part of this initiative is the development of high-resolution micro-fabricated columns. Rectangular cross-section, silicon/glass columns are etched in varying lengths, from 25cm to 3m. Both dynamic and static stationary phase deposition techniques on micro-fabricated columns are evaluated using height equivalent of a theoretical plate versus average linear carrier gas velocity and temperature programmed peak capacity. Band broadening contributions in rectangular cross section channels are modeled and compared to experimental data. Complex mixture analysis on short chromatographic columns is a challenge as column separation power scales with length. The burden of selectivity in an instrument can be shared through selective pre-concentration, thermal and pneumatic tunable selectivity, and spectrometric detection. This work reports the use of stop-flow tunable selectivity using a dual column ensemble of micro-fabricated columns with differing stationary phases. Selective detection is demonstrated through integration with a micro-fabricated differential mobility spectrometer (DMS). The second dimension separation, the DMS, separates and detects ionized components based on their differential mobilities through applied RF and DC fields in the sensor chip. Design features and performance data of the system will be presented.
BIO: Gordon Randall Lambertus was born in Terre Haute, IN, in 1980. He received a B.S. in Chemistry, a B.A. in Psychology, and a minor in Mathematics from Indiana University in Bloomington, Indiana in the spring of 2002. As an undergraduate summer research student, he worked with Dr. Phil Stevens in the Indiana University School of Public and Environmental Affairs on measurements of the kinetics of the OH-initiated oxidation of alpha-pinene. During his undergraduate career, he served as an Associate Instructor in the Department of Chemistry for two years. He received his M.S. in Analytical Chemistry from the University of Michigan in Ann Arbor, MI in 2004, after doing work in the Development, Evaluation, and Application of Silicon Microfabricated Separation Columns. He is currently pursuing his Ph.D. in the research lab of Dr. Richard Sacks in the University of Michigan Department of Chemistry in the same field.