DESIGN AND USE OF A THERMAL-CONDUCTIVITY DETECTOR AT REDUCED PRESSUREFOR TEMPERATURE-PROGRAMMED CAPILLARY GAS-CHROMATOGRAPHY

Based on a systematic study of the response characteristics of a therm al conductivity detector (TCD) at reduced pressure, a newly designed T CD was constructed and evaluated for use in temperature-programmed cap illary gas chromatography. The effective cell volume is as low as 1.3 mu l(physical volume 100 mu l), and there is no dead corner along the sensing path. Capillary columns of I.D. greater than or equal to 0.25 mm can couple directly with the TCD without a make-up gas. The detecto r response time is less than 0.1 s, the linear dynamic range is about four orders of magnitude and the detection limit is about 10 ppm (v/v) for octadecane. In the split injection mode, a simple configuration o f the capillary inlet system offers a constant carrier gas flow-rate t hrough the column with temperature-programmed operation. Practical exa mples are given that demonstrate the applicability of this detector an d the system.