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The performance of a fast gas chromatograph equipped with a Surfdce Acoustic Wave (SAW) detector i s evaluated in this p a p . Tbe instrument was developed for the rapld analysis of volatile oqanic compounds in air or water. Tbe SAWdetectol; the fist and only known integrating detector forgas chromatographs (GG), operates by responding to the muss of material exiting the GC column. Material adhering to the SAWsurface changes its operating frequency, which & detected by the system electronics and converted into a chromatogram. The system requires no high voltages or radioactive ionization sources, and is compact andportable. The millisecond response of the detector allows high speed analysis-measured in seconds-to takeplace. Thepformance of the GUSAWsystem is comparable to laboratory GCs in terms of limit of detection, precision, accuracy, and interference while screening environments in essentially real time (10 seconds). The results of the instrument evaluation for 10 common organic compounds in air and water matrices arepresented. INTROWCTlONUsing portable instruments to analyze semi-volatile and volatile organic compounds (VOCs) is gaining popularity for use in field applications [ll. Accurate, high speed measurements performed in the field can substantially reduce the cost of analysis. For VOCs, a number of field screening instruments, such as Gas Chromatographs (GCs), have emerged. But, there is still a lack of instruments versatile enough to analyze a wide range of organic compounds. GCs are an effective tool, but their usefulness as a field tool can be limited by retention times of several minutes, or even more for relatively simple separations. Because there is frequently no pre-concentration of the sample, the limits of detection (LOD) and quantitation (LOQ) may not be adequate for many applications 12, 31.Ongoing research has shown that GC analysis speed can be significantly improved 14-61, and that detection of organics and inorganics can be enhanced with the use of a Surface Acoustic Wave (SAW) sensor I7, 81. Until recently, however, no major breakthroughs in GC design had resulted in sub-minute analysis of VOCs [9, 101. This paper details the development and application of a novel field portable GC system equipped with a SAW detector. Performance results are given for a SAW analyzer that was subjected to a number of tests in the laboratory and field surroundings. These test results show that it is possible to speciate and quantlfy a wide range of environmental pollutants in near real time (less than 10 seconds) with good precision and accuracy. TECHNOLOGY DESCRIPTIONElectronic Sensor Technology (EST) has developed the model 7100 Fast GC to meet the needs of a field portable gas chromatograph [lll. The 7100, shown in Figure 1, is a high speed GC that utilizes a new type of detector based upon SAW sensor technology. This novel detector, coupled with proprietary GC technology, enables chromatographic measurements of soil, water, and air to be performed in less than 10 seconds, The SAW sensor and fast...

A new thermal conductivity detector based on a lithium niobate surface acoustic wave (SAW) resonator has been fabricated for use in a gas chromatograph. The device exploits the large temperature coefficient of LiNbO3 to detect low concentrations of CO2 in air by sensing the change in the thermal conductivity of a helium camer gas and the CO2 exiting the capillary gas chromatograph column. The LiNb03 resonator is maintained at 150oC and is held in close proximity (0.2-0.3 mm) to the exit of the capillary column which is maintained at 5OOC. Heat loss from the LiNb03 is primarily due to the thermal conductivity of the gas exiting the capillary column such that changes in the constituency of the gas result in temperature changes on the surface of the resonator. The surface temperature change is monitored by recording the resulting frequency change in a 342 MHz SAW resonator controlled oscillator circuit. The entire system is small, battery powered and rugged enough to monitor green house gases in remote field sites throughout the world.