Dynamic characteristics of a microthermochemical detector for gas chromatography
Abstract
Since its introduction in 1952, the method of gas chromatography has found wide application in various laboratories whose needs led to the development of a variety of detection devices. To date, about 50 detectors with universal, selective and specific characteristics have been proposed for gas chromatography.
Pronounced tendency of modern analytical chemistry, including gas chromatography, is miniaturization chromatography apparatus (columns, dispensing devices, detectors) allowing operatively perform complex analyzes of natural and manmade objects on MEMS low capacitance column using detectors, fabricated using silicon technology [1]. One of these detectors is a microcircuit based on film thermo-sensitive elements, the main technical characteristics of which were considered in [2-3].
For the purpose of increase in sensitivity and a precision of detecting the micro-thermochemical detector has been developed for a gas chromatography. The detector has working and comparative sensitive elements which are included in the bridge measuring scheme and are in one working camera of the detector, no more than 0.15 ml. Besides, the detector has two directing screens located parallel to platinum threads and also the calibrated sections for uniform distribution of a gas stream to working and comparative platinum threads. The developed detector allows to reduce considerably the level of fluctuation noise and drift of a zero signal due to compensation of influence of change of temperature, a consumption of gas carrier, supply voltage, etc.
Use of the differential bridge scheme when working and comparative platinum threads are in one flowing camera of the detector, allows to raise a limit of detecting of the microthermochemical detector on two orders in comparison with the known thermochemical detector of the gas chromatograph the Crystal of 5000.1 (Hromatek). Results of pilot studies have shown that use of MTCHD allows to increase for 10% lag effect in comparison with MTCD and to approach almost inertialess detector on ionization in a flame
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References
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