Direct resistive heating and temperature measurement of metal- clad capillary columns in gas chromatography and related separation techniques

摘要

An improved system and method for high resolution gas chromatography (GC) is disclosed. This invention involves the use of fused silica open tubular capillary columns having a conductive exterior coating and an arrangement for electrically coupling a power source to such coating, whereby it is now possible to effect direct resistive heating of the capillary column while controlling the temperature thereof. Such control is achieved by measurement of the resistance of the conductive coating, correlating such resistance with the temperature of the column and increasing or decreasing the electrical power supplied to such coating, as appropriate, to effect the desired adjustment in column temperature. Because of the low thermal mass of the column and the conductive coating, temperature changes can be effected readily thereby improving the speed of such separation and reducing the time interval between resolution of successive samples. In the preferred embodiments of this invention, the system is incorporated in what is referred to as "short column" gas chromatography instrumentation and thus suitable for "non-selective" detection systems or selective detection methods. Because of the relative compact nature and low power demands of the system of this invention, such system can be operated as a portable unit.