Sputtered alumina as a novel stationary phase for micro machined gas chromatography columns.

Silica and graphite sputtering have previously been reported as novel solid stationary phase deposition techniques for micro gas chromatography columns. As a conventional solid stationary phase in gas chromatography, compatible with sputtering yet so far unreported, alumina was evaluated in this study. Alumina sputtered semi-packed micro columns were fabricated (including an activation step) and proved able to separate a mixture of volatile alkanes (C1-C4 with isomers) in less than 1 min. Kinetic and a thermodynamic evaluation led to calculation of 4,500 theoretical plates for ethane in 1.1 m (HETPmin = 250 µm) and a Gibbs free energy for propane of 30.2 kJ mol(-1), making this stationary phase's properties very close to those observed with silica-sputtered micro columns.

Review of stationary phases for microelectromechanical systems in gas chromatography: feasibility and separations.

This review covers the recent development of stationary phases for chip-based gas chromatography (GC). Portable systems for rapid and reliable analysis are urgently needed. One way to achieve this is to miniaturize the entire analysis. Because the column is the central component of the GC system and determines the feasibility and quality of separation, this review focuses on stationary phases reported in the literature and their use in different fields during the last two decades, with emphasis on different methods for introducing the stationary phase into the GC column.

Temperature-programmed sputtered micromachined gas chromatography columns: an approach to fast separations in oilfield applications.

In a previous study, a new stationary phase deposition technique for micromachined gas chromatography columns was presented. The rerouting of the sputtering technique to this purpose enabled collective and reproducible fabrication of microcolumns in a silicon wafer. Silica-sputtered micromachined columns showed promising separations of light alkanes in isothermal conditions. In order to go beyond the limitations of isothermal separations, the columns were equipped with sputtered platinum filaments to enable high-speed and low-power temperature programming. The separation performances of temperature-programmed silica- or graphite-sputtered microcolumns were investigated: a separation of light alkanes (C1-C5) was completed in 9 s, and heavier alkanes (until C9), cyclic, isomeric, and unsaturated hydrocarbons were also successfully separated. Versatility of these microcolumns was demonstrated with a high-temperature C1-C2 separation and a C1-C5 separation with nitrogen as carrier gas instead of helium. By matching the requirements of a gas chromatography-based monitoring sensor, in terms of low-cost and industry-ready fabrication process, fast temperature programming and analysis, low power consumption, and good versatility (ambient temperature, carrier gas), these columns should be used in various applications related to oilfield gas analyses.

Silica sputtering as a novel collective stationary phase deposition for microelectromechanical system gas chromatography column: feasibility and first separations.

Since the late 1970s, approaches have been proposed to replace conventional gas chromatography apparatus with silicon-based microfabricated separation systems. Performances are expected to be improved with miniaturization owing to the reduction of diffusion distances and better thermal management. However, one of the main challenges consists in the collective and reproducible fabrication of efficient microelectromechanical system (MEMS) gas chromatography (GC) columns. Indeed, usual coating processes or classical packing with particulate matters are not compatible with the requirements of collective MEMS production in clean room facilities. A new strategy based on the rerouting of conventional microfabrication techniques and widely used in electronics for metals and dielectrics deposition is presented. The originality lies in the sputtering techniques employed for the deposition of the stationary phase. The potential of these novel sputtered stationary phases is demonstrated with silica sputtering applied to the separation of light hydrocarbons and natural gases. If kinetic characteristics of the sputtered open tubular columns were acceptable with 2500 theoretical plates per meter, the limited retention and resolution of light hydrocarbons led us to consider semipacked sputtered columns with rectangular pillars allowing also significant reduction of typical diffusion distances. In that case separations were greatly improved because retention increased and efficiency was close to 5000 theoretical plates per meter.