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A High Performance Hand-Held Gas Chromatograph


 The Microtechnology Center of Lawrence Livermore National Laboratory has developed a high performance hand-held, real time detection gas chromatograph (HHGC) by Micro-Electro-Mechanical-System (MEMS) technology. The total weight of this hand-held gas chromatograph is about 5 lbs., with a physical size of 8″ × 5″ × 3″ including carrier gas and battery. It consumes about 12 watts of electrical power with a response time on the order of one to two minutes. This HHGC has an average effective theoretical plate of about 40k. Presently, its thermal sensitive detector at PPM limits its sensitivity.
 Like a conventional G.C., this HHGC consists mainly of three major components: 1) the sample injector, 2) the column, and 3) the detector with related electronics. The present HHGC injector is a modified version of the conventional injector. Its separation column is fabricated completely on silicon wafers by means of MEMS technology. This separation column has a circular cross section with a diameter of 100 μm. The detector developed for this hand-held G.C. is a thermal conductivity detector fabricated on a silicon nitride window by MEMS technology. A normal Wheatstone bridge is used. The signal is fed into a PC and displayed through LabView software.