In recent years, the need for measurement and detection of samples in situ or with very small volume and low concentration (low and sub-parts per billion) is a cause for miniaturizing systems via microelectromechanical system (MEMS) technology. Gas chromatography (GC) is a common technique that is widely used for separating and measuring semi-volatile and volatile compounds. Conventional GCs are bulky and cannot be used for in situ analysis, hence in the past decades many studies have been reported with the aim of designing and developing chip-based GC. The focus of this review is to follow and investigate the development and the achievements in the field of chip-based GC and its components from the beginning up to the present.

Through the years with on-a-chip gas chromatography: a review

Microchip gas chromatography columns, interfacing and performance

A micro-gas pressure driving apparatus includes a miniature gas transportation module and a miniature valve module. The miniature gas transportation module includes a gas inlet plate, a fluid channel plate, a resonance membrane and a piezoelectric actuator. A first chamber is defined between the resonance membrane and the piezoelectric actuator. After the piezoelectric actuator is activated to feed a gas through the gas inlet plate, the gas is transferred to the first chamber through the fluid channel plate and the resonance membrane and then transferred downwardly. Consequently, a pressure gradient is generated to continuously push the gas. The miniature valve module includes a gas collecting plate, a valve membrane and a gas outlet plate. After the gas is transferred from the miniature gas transportation module to the gas-collecting chamber, the gas is transferred in one direction, so that a pressure-collecting operation or a pressure-releasing operation is selectively performed.

Micro-gas pressure driving apparatus

Recent advances in analysis of precursors, simulants and degradation products of chemical warfare agents (CWA) are reviewed. Fast and reliable analysis of precursors, simulants and CWA degradation ...

Analysis of the Precursors, Simulants and Degradation Products of Chemical Warfare Agents.

This paper reports the development of a new class of high-performance microfabricated separation columns called high-density semi-packed columns (HDSPCs). These columns are realized by using a meter long and 145 μm-wide silicon microchannel design with embedded circular micropillars (15 μm diameters) and 5 μm post spacing (perpendicular to the gas flow). The HDSPCs are coated using our previously developed atomic layer deposition (ALD) based aluminium oxide and silane functionalized thin adsorbent film. Moreover, in this study we optimize both ALD deposition temperature (100 °C, 150 °C, 250 °C and 300 °C) and film thickness (10 nm, 20 nm and 30 nm) using different chromatographic parameters (plate number, peak-to-peak resolution, and separation factor). Additionally, the thermodynamic characteristics of these silane functionalized/ALD films are also studied using Van’t Hoff plots. These columns with optimized stationary phases are able to provide ≈8000 effective plates/meter and successfully separate a custom made hydrocarbon sample mixture with high peak-to-peak resolution.

/pdf/high-density-semipacked-separation-columns-with-optimized-238fntbnon.pdf

High density semipacked separation columns with optimized atomic layer deposited phases

To achieve both high speed and separation efficiency in the separation of a mixture of nerve and blister agent simulants, a high-aspect-ratio micro-fabricated multi-capillary column (MCC, a 50-cm-long, 450-μm-deep, and 60-μm-wide four-capillary column) was fabricated by the application of the microelectromechanical system (MEMS) techniques. Mixtures of chemical warfare agent (CWA) simulants - dimethyl methylphosphonate (DMMP), triethyl phosphate (TEP), and methyl salicylate - were used as samples. The fabricated MCC allowed for the separation of all the components of the gaseous mixture within 24 s, even when the difference in boiling point was 4°C, as in the case of TEP and methyl salicylate. Furthermore, interfering agents - dichloromethane, ethanol, and toluene - were also included in the subsequent gaseous mixture samples. The boiling point of these six components ranged from 78°C to 219°C. All six components were clearly separated within 70 s. This study is the first to report the clear separation of gas mixtures of components with close boiling points. The column efficiency was experimentally determined to be 12,810 plates/m.

/pdf/high-separation-efficiency-micro-fabricated-multi-capillary-1cewmgavpd.pdf

High-separation efficiency micro-fabricated multi-capillary gas chromatographic columns for simulants of the nerve agents and blister agents.

The invention discloses a miniature gas enricher with membranes on double surfaces An upper silicon wafer and a lower silicon wafer are bonded to form a miniature gas chamber, one or more suspension membranes are arranged on each silicon wafer, silicon corresponding to the suspension membranes are completely removed to form an empty cavity, film heaters are arranged on the suspension membranes, and an adsorption film is coated on the inner wall of each suspension membrane The suspension membranes are arranged on double surfaces of the enricher so that the areas of the adsorption films on the membranes are increased In addition, on the basis of keeping advantages of small heat capacity, quick heating rate, small power consumption and the like of the membrane type enricher, the areas of the adsorption films are increased and enriching efficiency is improved

Miniature gas enricher with membranes on double surfaces

A double-sided diaphragm micro gas-preconcentrator has a micro-gas chamber which is formed by bonding an upper silicon substrate with a lower silicon substrate. One or more suspended membranes are provided on every silicon substrate. The silicon where the suspended membrane is provided is completely removed for forming a cavity. A thin-film heater is deposited on every suspended membrane. A sorptive film is coated on an inner wall of every suspended membrane. Thus, the upper and lower sides of the preconcentrator in the present invention are suspended membranes, which improve the area of the sorptive film on the diaphragm. As a result, the preconcentrating factor is improved while keeping the small heat capacity, fast heating rate, and low power consumption features of the planar diaphragm preconcentrator.

Double-sided diaphragm micro gas-preconcentrator

A double-sided diaphragm micro gas-preconcentrator has a micro-gas chamber which is formed by stacking an upper silicon substrate with a lower silicon substrate with a back-on-face configuration. One or more suspended membranes are provided on every silicon substrate. The silicon where the suspended membrane is provided is completely removed for forming a cavity. A thin-film heater is deposited on every suspended membrane. A sorptive film is coated on an inner wall of every suspended membrane. Thus, the upper and lower sides of the preconcentrator in the present invention are suspended membranes, which improve the area of the sorptive film on the diaphragm. As a result, the preconcentrating factor is improved while keeping the small heat capacity, fast heating rate, and low power consumption features of the planar diaphragm preconcentrator.

Double-sided diaphragm micro gas-preconcentrator with a back-on-face configuration

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Papers

High-separation efficiency micro-fabricated multi-capillary gas chromatographic columns for simulants of the nerve agents and blister agents.

Miniature gas enricher with membranes on double surfaces

Double-sided diaphragm micro gas-preconcentrator

Double-sided diaphragm micro gas-preconcentrator with a back-on-face configuration