title: Evaluation of a microfabricated thermal modulator for comprehensive two-dimensional microscale gas chromatography.
abstract: A microfabricated thermal modulator (μTM) designed for ultimate use in a comprehensive two-dimensional microscale gas chromatography (μGC × μGC) system is evaluated. The 2-stage device measures 13 mm (l) × 6 mm (w) × 0.5 mm (h) and consists of two interconnected serpentine etched-Si microchannels suspended from a thin Pyrex cap and wall-coated with PDMS (polydimethylsiloxane). The chip is mounted within a few tens of micrometers of a thermoelectric cooler that maintains both stages at a baseline temperature between -35 and -20 °C in order to focus analytes eluting from an upstream separation column. Each stage is heated to 210 °C sequentially at a rate as high as 2400 °C/s by independent thin-film resistors to inject the analytes in consecutive fractions to a downstream column, and then cooled at a rate as high as -168 °C/s. The average power dissipation is only ∼10 W for heating and 21 W for cooling without using consumable materials. In this study, the outlet of the μTM is connected directly to a flame ionization detector to assess its performance. Following a demonstration of basic operation, the modulated peak amplitude enhancement (PAE) and full-width-at-half-maximum (fwhm) are evaluated for members of a series of n-alkanes (C(6)-C(10)) as a function of the rim and stage temperatures; modulation period, phase, and offset; analyte concentration; and carrier-gas flow rate. A PAE as high as 50 and a fwhm as narrow as 90 ms are achieved for n-octane under optimized conditions.
authors.affiliation: Center for Wireless Integrated Microsystems (WIMS), University of Michigan, Ann Arbor, Michigan 48109-2122, United States.
authors.forename: Sung-Jin
authors.initials: SJ
authors.lastname: Kim
authors.forename: Gustavo
authors.initials: G
authors.lastname: Serrano
authors.forename: Kensall D
authors.initials: KD
authors.lastname: Wise
authors.forename: Katsuo
authors.initials: K
authors.lastname: Kurabayashi
authors.forename: Edward T
authors.initials: ET
authors.lastname: Zellers
mesh_terms: D000473:Alkanes / Q000032:analysis*; D002849:Chromatography, Gas / Q000295:instrumentation* / Q000379:methods; D004129:Dimethylpolysiloxanes / Q000737:chemistry; D004867:Equipment Design; D055616:Microtechnology; D015203:Reproducibility of Results; D013696:Temperature
chemical_list: D000473:Alkanes; D004129:Dimethylpolysiloxanes; C013830:baysilon