**1. Introduction**

Volatile organic compounds (VOCs) are the premise of pollutants for forming PM 2.5 or heavy haze and choking smog, so monitoring VOCs is a very important measure for preventing environmental pollution. In addition, rapid detection of VOCs is also very necessary in some on-site detection, including indoor air quality, industrial emissions control, air pollution emergency in urban area, rapid detection of explosives in public place, and breath analysis. Therefore, fast, on-site, high-precision, and portable systems are the pressing need for providing real-time monitoring for quantification and identification analysis of environmental samples.

Conventional gas chromatography (GC), which is a powerful and commonly used analytical technique, has become the premier technique for separation and analysis of harmful com‐ pounds due to its high resolving power. However, in some cases, gas samples need to be collected in the field and analyzed in the laboratory using conventional GC, which makes this process inefficient and inconvenient in field use.

As MEMS technology matures, micro gas chromatographic systems (µGC) [1-3] have a prospect future with some advantages of small volume, rapid analysis, and less power consumption compared with conventional GC systems, which are very urgent to be used for analyzing the complicated gas mixtures. Therefore, these attributes make these systems based on microelectromechanical systems (MEMS) technology attractive for a number of applica‐ tions involving on-site monitoring of environmental samples, and this research direction is under intensive research.

In this chapter, we reported the design, fabrication, and characterization of micro preconcentrator, micro GC column, and mini photoionization detector (mini PID). Then a mini

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GC system based on mini PID was integrated with the micro GC column and the micro preconcentrator.
