Novel Microanalytical GC Platforms

     Gas Chromatography (GC) is a key analytical technique for analyzing volatile organic compounds in complex samples.  Conventionally, such samples are taken from various points of interest, for example an industrial setting, and then transported to a central laboratory where GC analysis can be performed.  While effective, this protocol prevents the realization of a more desirable rapid process, in which the measurement result can be obtained quickly in-situ.  In recent years, a major analytical trend in this regard has been to miniaturize conventional laboratory instrumentation into portable handheld units.  Perhaps the greatest advances toward this end have been made in the area of microfluidic devices.  Accordingly, the latter is increasingly being adapted to GC technology.

     Microfluidic devices essentially comprise very small channels etched into a silicon wafer/chip that is often the size of a credit card.  Typically, these silicon substrates provide a useful medium for achieving narrow micron-scale channels that can be quite small compared to conventional capillary GC tubing.  However, these devices are often sealed with a cover plate bonded to the chip surface.  Since borosilicate is frequently used for this, it can lead to thermal mismatching, device leakage, and thermal gradients that erode separation efficiency.  As well, since these devices often lie in one plane, this hinders the development of other useful 'on-chip' components in 3D formats.  Of note, the integration of other items around micro-channels (e.g. supporting electronics, mechanical parts) is typically very difficult with silicon-based devices.  Often, procedures to integrate such pieces onto silicon-based chips are complex, costly, long and require specialized clean rooms and technical personnel to accomplish.  As a result, such critical components are often left 'off-chip' during testing, impeding the development of truly portable GC systems.

     Low Temperature Co-Fired Ceramics (LTCC) are a potentially useful route to realizing fully functional/portable GC devices.  LTCC technology evolved from the electronics industry as a simple, high volume, low-cost fabrication method to produce multi-layer circuit boards.  Thus, these devices possess the ability to readily incorporate micro-fluidic designs and supporting metal components in a 3D format.  Since they are inherently rugged and stable up to relatively high temperatures and pressures, LTCC devices also hold great potential for chromatography.  Such properties allow detectors, mixers, ample prep stations, flow controllers, etc. to all be grouped on one sturdy platform.  In addition to the rapid prototyping and low cost of LTCC, it requires no special facilities or extensive training to perform.  As such, developments of this technology to on-chip liquid chromatography devices are emerging and have shown LTCC methods to be very useful.  However, examples of LTCC in GC are sparse despite its promise in this area.  We are exploring the potential of LTCC-based devices in portable microanalytical GC systems.