METHOD AND THERMAL CONDUCTIVITY DETECTOR

摘要

A thermal conductivity detector includes a heatable resistive detector configured to be physically arranged in an analytes flow eluting from a chromatography column and electrically arranged with resistors in separate arms of a measuring bridge, an amplifier which detects differential voltage between two opposite nodes of the bridge and applies an output voltage to other opposite nodes of the measuring bridge to maintain the detector at a constant operating temperature, and an additional resistor with a controllable switch in parallel connected in series with the detector or resistor arranged in one arm of the bridge, where the switch is periodically turned on and off at a predetermined duty cycle and/or controlled by information on characteristic times-of-arrival of analytes at the detector to compensate for operating temperature uncertainties due to manufacturing variations of the resistors and/or to allow for processing small and large peaks of a chromatogram with highest available resolution.

主权项

1. A thermal conductivity detector for a gas chromatograph comprising:
a heatable resistive detector element configured to be physically arranged in a flow of analytes eluting from a chromatography column and electrically arranged with resistors in separate arms of a measuring bridge; an additional resistor with a controllable switch in parallel and connected in series with the heatable resistive detector element or a resistor in one arm of the measuring bridge; an amplifier configured to detect a differential voltage between two opposite nodes of the measuring bridge and to apply an output voltage to other opposite nodes of the measuring bridge to maintain the heatable resistive detector element at a constant operating temperature; and a controller configured to provide a control signal to the switch to adjust the operating temperature; wherein the control signal is a pulse-width modulated voltage with a period lower than a thermal time constant of the detector element.