ASSESSMENT OF SOME POSSIBILITIES FOR IMPROVING THE PERFORMANCE OF GAS-CHROMATOGRAPHIC THERMAL-CONDUCTIVITY DETECTORS WITH HOT-WIRE SENSITIVE ELEMENTS

The possibilities for improving the performance of gas chromatographic thermal conductivity detectors (TCD) by using hot-wire sensitive elem ents with appropriate design and increased resistance were studied. It is shown that the design of the traditional TCD with one-way heat con duction, and also the new kind of sensitive element design with two-wa y heat conduction, in which one of the filament leads is assembled ins ide the coil along its axis, can be optimized. The best TCD performanc e can be achieved if the sensitive element spiral pitch is minimal and the spiral radius is equal to r(c)/e in the case of one-way heat cond uction and to the mean radius (r(c) + r(1))/2 in the case of two-way h eat conduction, where r(c) and r(1) are the radiuses of the gas cavity and of the central filament lead, and e approximate to 2.7 is the Nap ierian number. Further, the optimization of the sensitive element desi gn provides an increase in its resistance, which additionally improves the TCD performance. Following this approach and taking into account the ultimate capabilities of modern electronics, two new optimized des igns of the sensitive elements with about 650 Omega resistance at 0 de grees C, that after the numerical estimations presented could improve the TCD performance more than tenfold, are developed and proposed for further experimental studies.