Design, Fabrication, and Evaluation of Microfabricated Columns for Gas Chromatography

Abstract

The design, fabrication, and performance of gas chromatography columns etched in silicon substrates are described. Deep reactive-ion etching formed the 3-m-long, 150-microm-wide, 240-microm-deep rectangular cross section channels. A glass cover plate was anodically bonded to the remaining surface of the substrate forming the gastight channel. For some of the columns, the silicon channels were oxidized before the channels were sealed with the glass plates. Fused-silica capillary connecting tubes were sealed into ports on the edge of the 3.2-cm x 3.2-cm substrate chips. Dynamic coating was used to deposit a film of nonpolar dimethyl polysiloxane or moderately polar trifluoropropylmethyl polysiloxane stationary phase. The columns were evaluated in a conventional benchtop GC instrument with split injection and flame ionization detection. Column efficiency was evaluated by the use of plots of height equivalent to a theoretical plate versus average carrier gas velocity using both hydrogen and air as carrier gases. The number of theoretical plates measured at the average carrier gas velocity giving the minimum plate height ranged from 4600 to 8200 plates for the dimethyl polysiloxane columns and from 3500 to 5500 plates for the trifluoropropylmethyl polysiloxane columns. Minimum plate height was significantly smaller with air as carrier gas. For the nonpolar phase, the nonoxidized surface gave approximately 1500 plates more than the oxidized surface for both carrier gases. For the polar phase, the oxidized surface gave approximately 200 plates more than the nonoxidized surface. Isothermal chromatograms of a 20-component multifunctional mixture and temperature-programmed chromatograms of a normal alkane mixture are presented.

Novel synthesis of thick wall coatings of titania supported Bi poisoned Pd catalysts and application in selective hydrogenation of acetylene alcohols in capillary microreactors

“…The method reported in this work addresses these problems by using an elevated temperature and pressure as opposed to conventionally used vacuum-based techniques. [34][35][36][37] The temperature of the copper guide tubing at the entrance to the oven (Fig. 2) increases linearly from about 350 K (air-cooled side) to the oven temperature.…”

“…Static coating implies filling the reactor with a precursor solution, closing one end of the capillary and applying vacuum to the other end to facilitate evaporation. 34,35 The static coating method offers a simple way of achieving uniform coating synthesis with a thickness that can be adjusted by changing the precursor solution concentration. [35][36][37] Other experimental parameters such as the evaporation temperature and the pressure should be optimised to slow the evaporation rate required to obtain uniform coatings.…”

Hand-portable gas chromatograph-toroidal ion trap mass spectrometer (GC-TMS) for detection of hazardous compounds

“…Power reduction and short analysis time are the main challenges for the GC component of portable GC-MS. Microchip-based GC has certainly demonstrated both reduced analysis time and reduced power consumption; however, it has proven difficult to evenly coat the separation channels and to connect them to injection systems and detectors, and their separation performance has not yet matched the high efficiency of conventional fused silica capillary columns [12]. Another approach has been to use low thermal mass GC that relies on resistively heating the capillary column instead of using a bulky convection oven [11, 14, 40 -42].…”

Carbon Nanotube Stationary Phase in a Microfabricated Column for High-Performance Gas Chromatography

“…These drawbacks have hindered miniaturization of GC instruments for which a wide range of applications is foreseen [1]. Recent developments in the micro-fabrication of GC systems using micromachining technology have demonstrated the potential for reductions in size, power consumption, and analysis time compared to conventional GC systems [2][3][4][5][6][7].…”