Development of a Smart Multi-Channel Two-Dimensional Micro-Gas Chromatography.

Abstract

Micro-gas chromatography (GC), which is capable of conducting fast on-site gas analysis, has broad applications in various fields, such as environmental monitoring, homeland security, and anti-terrorism. This dissertation presents the development of a smart multi-channel two-dimensional (2-D) micro-GC, which not only greatly improves the separation capability but also resolves many disadvantages associated with traditional 2-D micro-GCs. The proposed micro-GC consists of a preconcentrator to sample gas analytes, microfabricated separation columns to conduct rapid sample separation, on-column optical detectors to detect analytes, and pumps to provide fluidic flow. The working principle, fabrication method, and calibration of each component are discussed in detail. One-dimensional micro-GC sub-system is also tested to have improved separation capability and shortened analysis time. Finally, a smart multi-channel 2-D micro-GC is demonstrated. In this system, an on-column gas detector and a flow routing system are installed between the first column and multiple second columns. The eluent from the first column is monitored in real-time and decision is then made to route the eluent to one of the second columns for further separation. As compared to conventional 2-D micro-GC systems, the greatest benefit of the smart 2-D micro-GC is the enhanced separation capability of the second column and hence the overall 2-D GC performance. All the second columns are independent of each other, whose coating, length, flow rate and temperature can be customized for best separation result. In particular, there is no limit on the second column length and separation time in our architecture. Such flexibility is critical when long second separation is needed for optimal gas analysis. In addition, the smart micro-GC is advantageous in terms of elimination of the power intensive thermal modulator, higher peak amplitude enhancement, simplified 2-D chromatogram re-construction and potential scalability to higher dimensional separation. Several important applications are explored based on this system. First, it analyzes a mixture of plant emitted volatile organic compounds (VOCs) that can provide highly specific information for use in agriculture and defense. Then, it is employed for the separation of workplace hazardous VOCs, and rapid detection and identification of target gas analytes from interference background.