Portable gas chromatograph with integrated components

In the paper, a portable gas chromatograph with silicon/glass integrated micromachined flushed injector and doubled thermal conductivity detectors (TCD) has been presented. The injector has two symmetrical dosing loops, each of 7 mul volume and one fast injection microvalve, pneumatically operated. All parts of the injector are integrated on 35 x 35 x 2.5 mm(3) glass/silicon/glass die. Teflon coated thin polyimide foil is applied as the moving actuator of the microvalve of the injector. Three types of TCDs have been tested. In the first type of TCD, four thin-film Pt heaters/thermoresistors made on thin silicon nitride CVD deposited membrane suspended over deeply etched in a silicon substrate two channels, are applied. In the next two TCDs, miniature spirals made of thin Pt solid wire are assembled inside glass/silicon chip. Two configurations of spirals position have been tested: in-line serial and in-line parallel. Computer simulations, supported by experiments have indicated better parameters of TCD with parallel configuration of spirals. The TCDs with Pt spirals are resistant against carrier gas decays. In the portable gas chromatograph two capillary columns are used: active (molecular sieve) and passive. Columns and co-working TCD are thermally stabilized in an oven equipped with a thick-film heater made on polyimide foil. The instrument is equipped with built-in microcomputer with two 16-bit microprocessors and is operated (controlled) by an external portable PC. All important parameters of analysis (possible single or continuous mode of work) are adjusted electronically, as well as data acquisition and preparing of the complete analysis effect in the form of chromatograms and tables indicating qualitative and quantitative composition of gas mixture. The instrument is able to work in on-line continuous measurements, tests made for artificial atmosphere of deep mining industry have shown successful work of the instrument. (C) 2004 Published by Elsevier B.V.