Progressive Cellular Architecture in Microscale Gas Chromatography for Broad Chemical Analyses

Abstract

Gas chromatography is widely used to identify and quantify volatile organic compounds for applications ranging from environmental monitoring to homeland security. We investigate a new architecture for microfabricated gas chromatography systems that can significantly improve the range, speed, and efficiency of such systems. By using a cellular approach, it performs a partial separation of analytes even as the sampling is being performed. The subsequent separation step is then rapidly performed within each cell. The cells, each of which contains a preconcentrator and separation column, are arranged in progression of retentiveness. While accommodating a wide range of analytes, this progressive cellular architecture (PCA) also provides a pathway to improving energy efficiency and lifetime by reducing the need for heating the separation columns. As a proof of concept, a three-cell subsystem (PCA3mv) has been built; it incorporates a number of microfabricated components, including preconcentrators, separation columns, valves, connectors, and a carrier gas filter. The preconcentrator and separation column of each cell are monolithically implemented as a single chip that has a footprint of 1.8 × 5.2 cm2. This subsystem also incorporates two manifold arrays of microfabricated valves, each of which has a footprint of 1.3 × 1.4 cm2. Operated together with a commercial flame ionization detector, the subsystem has been tested against polar and nonpolar analytes (including alkanes, alcohols, aromatics, and phosphonate esters) over a molecular weight range of 32–212 g/mol and a vapor pressure range of 0.005–231 mmHg. The separations require an average column temperature of 63–68 °C within a duration of 12 min, and provide separation resolutions >2 for any two homologues that differ by one methyl group.

Performance Improvement of Glass Microfiber Based Thermal Transpiration Pump Using TPMS

“…Micro-electromechanical systems (MEMS) have become more interesting to various research groups over the past few decades. Micropumps are important components for many microscale applications such as micro gas chromatographs [ 1 , 2 ], small satellite propulsion [ 3 ], heat pumps [ 4 ] and SOFC power generators [ 5 ]. In general, pumps or compressors use mechanical work to drive fluid from a low pressure side to a high pressure side, but at a microscale, they have to operate at extremely high speed to generate enough flow [ 6 , 7 ] while consuming a lot of power.…”

Highly Integrated μGC Based on a Multisensing Progressive Cellular Architecture with a Valveless Sample Inlet

“…The analytical performance of a μGC can be affected by the valves located in critical segments of the flow path connecting the sample inlet, the preconcentrator, the separation columns, and the detectors. Some systems incorporate inert and even heated microvalves, , which require specialized fabrication and assembly. Some systems have used Dean’s switches or eliminated valves by merging the sampling and separation flow paths and using a bidirectional pump to provide the sampling and separation flow .…”

“…Some systems have used Dean’s switches or eliminated valves by merging the sampling and separation flow paths and using a bidirectional pump to provide the sampling and separation flow . In general, although the majority of valves are located outside of the critical flow path segments, a valve is still used between the sample inlet and the preconcentrator. ,, This valve, which is opened during sampling and closed during separation, is typically a commercial off-the-shelf (COTS) component. ,,,,, Unfortunately, most COTS miniature valves are not chemically inert and none of them have heating capability.…”

“…5−7 A μGC with a progressive cellular architecture, a new architecture that has been recently reported by our group, incorporates multiple cells, each comprised of a preconcentrator and a column tailored for a different range of analytes. 8 The sample is first drawn through the staggered preconcentrators, sorting the analytes by volatility; the analysis is performed separately in each cell. The preconcentrator arrangement used in this architecture is similar to but distinct from the previously reported multibed preconcentrators, 9 as the analyte sorting that is inherently provided by the different sorbents is segregated by cells to allow individual injections into different separation columns.…”

“…17 In general, although the majority of valves are located outside of the critical flow path segments, a valve is still used between the sample inlet and the preconcentrator. 8,25,38 This valve, which is opened during sampling and closed during separation, is typically a commercial off-the-shelf (COTS) component. 10,12,13,35,37,38 Unfortunately, most COTS miniature valves are not chemically inert and none of them have heating capability.…”