High-performance micro-fabricated gas chromatography columns for complex mixture analysis.

摘要

Separations of volatile and semi-volatile organic compounds using high performance micro-fabricated columns with on-board heaters and temperature sensors are described. The research is part of a large collaboration project for the development of a completely autonomous micro-gas chromatograph (microGC), capable of separating and detecting complex mixtures for a wide range of applications. Improvements in column performance and integration into more complex systems are explored.;Initial separations were achieved using 3-m-long, square spiral channels, having rectangular cross sections of 150 x 240 microm and using a dynamic coating method for stationary phase deposition. This resulted in thicker than ideal stationary phases and poorer than expected column performance. A static coating method was developed, yielding thinner stationary phases, and in turn better performing columns. Total theoretical plates went from approximately 8000 plates, with the dynamic coating method, to approximately 12,000, with the static coating method.;Using on-board heaters and temperature sensors patterned on the silicon side of the columns, temperature programming without the use of a large convection oven has been achieved. Temperature programming ramps up to 1000°C/min have been achieved, separating C5-C15 in approximately 12s. Using a single 3-m-long nonpolar column and temperature programming, a 30-component mixture has been separated in less than six minutes. This mixture spans five orders of magnitude in vapor pressure range. This is the greatest number of components separated on a microfabricated column ever reported.;Increases in peak capacity were obtained by using dual column systems. The first system connected two microcolumns in series, temperature programming the two columns independent of each other. By varying column temperature, the elution order of components change and co-eluting compounds can be moved to areas of the chromatogram. The second system uses modulators to continuously focus and reinject compounds onto a shorter second column, allowing for separations over a two independent dimensions instead of a one-dimensional axis.;The microcolumns were integrated into a microfabricated testbed system. Evaluation of the system determined optimal performance and flow rate. Separations of complex mixtures were obtained on the system, and these are some of the most complex mixtures separated on this system to date.