Abstract
Gas chromatography is widely used to identify and quantify volatile organic compounds for applications ranging from environmental monitoring to homeland security. We investigate a new architecture for microfabricated gas chromatography systems that can significantly improve the range, speed, and efficiency of such systems. By using a cellular approach, it performs a partial separation of analytes even as the sampling is being performed. The subsequent separation step is then rapidly performed within each cell. The cells, each of which contains a preconcentrator and separation column, are arranged in progression of retentiveness. While accommodating a wide range of analytes, this progressive cellular architecture (PCA) also provides a pathway to improving energy efficiency and lifetime by reducing the need for heating the separation columns. As a proof of concept, a three-cell subsystem (PCA3mv) has been built; it incorporates a number of microfabricated components, including preconcentrators, separation columns, valves, connectors, and a carrier gas filter. The preconcentrator and separation column of each cell are monolithically implemented as a single chip that has a footprint of 1.8 × 5.2 cm2. This subsystem also incorporates two manifold arrays of microfabricated valves, each of which has a footprint of 1.3 × 1.4 cm2. Operated together with a commercial flame ionization detector, the subsystem has been tested against polar and nonpolar analytes (including alkanes, alcohols, aromatics, and phosphonate esters) over a molecular weight range of 32–212 g/mol and a vapor pressure range of 0.005–231 mmHg. The separations require an average column temperature of 63–68 °C within a duration of 12 min, and provide separation resolutions >2 for any two homologues that differ by one methyl group.
Highlights
The detection and quantification of volatile organic compounds (VOCs) is critical in many applications, such as environmental monitoring, homeland security, and agriculture
The progressive cellular architecture (PCA) reported in this work overcomes this compromise by incorporating a series of cells, each of which contains a preconcentrator and a separation column tailored to a specific volatility range of analytes (Figure 1)
This paper focuses on tailoring cells to the volatility range of targeted groups of analytes, the polarity of the preconcentrator and separation column in each cell can be tailored in principle
Summary
The detection and quantification of volatile organic compounds (VOCs) is critical in many applications, such as environmental monitoring, homeland security, and agriculture. The progressive cellular architecture (PCA) reported in this work overcomes this compromise by incorporating a series of cells, each of which contains a preconcentrator and a separation column tailored to a specific volatility range of analytes (Figure 1). In the PCA, because each column is tailored to a specific range of analytes, sufficient retention can be provided even for high-volatility analytes This alleviates the requirement for rapid preconcentrator heating and ultrasharp analyte injection. Conventional one-dimensional μGC architectures accommodate a moderate volatility range of analytes while providing moderate separation performance, and are best suited for applications that have a narrow range of targets and simple interferences. Two-dimensional μGC architectures accommodate a moderate volatility range of analytes while providing superior separation performance, and are best suited for applications that have a narrow range of targets but complex interferences.
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