title: Comprehensive two-dimensional gas chromatographic separations with a microfabricated thermal modulator.
abstract: Rapid, comprehensive two-dimensional gas chromatographic (GC × GC) separations by use of a microfabricated midpoint thermal modulator (μTM) are demonstrated, and the effects of various μTM design and operating parameters on performance are characterized. The two-stage μTM chip consists of two interconnected spiral etched-Si microchannels (4.2 and 2.8 cm long) with a cross section of 250 × 140 μm(2), an anodically bonded Pyrex cap, and a cross-linked wall coating of poly(dimethylsiloxane) (PDMS). Integrated heaters provide rapid, sequential heating of each μTM stage, while a proximate, underlying thermoelectric cooler provides continual cooling. The first-dimension column used for GC × GC separations was a 6 m long, 250 μm i.d. capillary with a PDMS stationary phase, and the second-dimension column was a 0.5 m long, 100 μm i.d. capillary with a poly(ethylene glycol) phase. Using sets of five to seven volatile test compounds (boiling point ≤174 °C), the effects of the minimum (T(min)) and maximum (T(max)) modulation temperature, stage heating lag/offset (O(s)), modulation period (P(M)), and volumetric flow rate (F) on the quality of the separations were evaluated with respect to several performance metrics. Best results were obtained with a T(min) = -20 °C, T(max) = 210 °C, O(s) = 600 ms, P(M) = 6 s, and F = 0.9 mL/min. Replicate modulated peak areas and retention times were reproducible to <5%. A structured nine-component GC × GC chromatogram was produced, and a 21 component separation was achieved in <3 min. The potential for creating portable μGC × μGC systems is discussed.
authors.affiliation: Center for Wireless Integrated MicroSensing and Systems, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: Gustavo
authors.initials: G
authors.lastname: Serrano
authors.forename: Dibyadeep
authors.initials: D
authors.lastname: Paul
authors.forename: Sung-Jin
authors.initials: SJ
authors.lastname: Kim
authors.forename: Katsuo
authors.initials: K
authors.lastname: Kurabayashi
authors.forename: Edward T
authors.initials: ET
authors.lastname: Zellers
mesh_terms: D002849:Chromatography, Gas / Q000295:instrumentation* / Q000379:methods*; D004867:Equipment Design; D007700:Kinetics; D055616:Microtechnology / Q000295:instrumentation* / Q000379:methods*; D015203:Reproducibility of Results; D013696:Temperature; D055549:Volatile Organic Compounds / Q000737:chemistry
chemical_list: D055549:Volatile Organic Compounds