Microfluidic valve geometries and possibilities for flow switching in gas chromatography

Classical two-dimensional separations in gas chromatography (GC) require switching systems to transfer the flow stream of carrier gas from the first to second dimension. This can be accomplished by valve systems, but is more suitably effected by pneumatic flow switching, such as the Deans' switch method. Recent developments in microfluidics and related micro-technologies should make gas phase switching much more effective. The capillary flow technology platform of Agilent Technologies exemplifies recent developments introduced to GC. Thus various Deans' switch pressure balanced devices, stream splitters, and column couplings bring new capabilities to analytical GC. We are uniquely placed to take advantage of the new devices, owing to our development of advanced operational methods in GC which can make use of microfluidic capillary couplings, and novel cryogenic approaches that deliver performance previously impossible with conventional methods. Multidimensional chromatographic flow switching to isolate pure compounds from complex mixtures suggests many potential applications for enhanced chemical analysis. Multiple dimensions of analysis, integrating capabilities for gas chromatography separations with different spectroscopic detection methods for chemical identification of isolated chemical species (including mass spectrometry, nuclear magnetic resonance and Fourier transform infrared) can be proposed. Applications in the essential oils and petrochemical area will be outlined.