THERMAL CONDUCTIVITY DETECTOR (TCD) FOR APPLICATIONS IN FAST GAS- CHROMATOGRAPHIC (GC)

摘要

The purpose of the present invention is to provide a new Thermal Conductivity Detector (TCD) specifically suited for fast Gas Chromatographic (GC) applications (gas analysis technique characterized by rapid analysis cycles). In the TCD of the invention, micro- electromechanical processing technique is used to fabricate a miniaturized device, which consists of two couples of platinum resistors put in a Wheatstone bridge configuration and suspended upon dielectric membranes at the centre of two flowing channels (reference channel and analytical channel). The novel aspect of the proposed layout, with respect to the prior art, consists in locating each couple of resistors over a single dielectric membrane, so that the length of the area occupied by each couple of resistors is shorter than a sample gas packet length to be analyzed, which prevents the formation of artifacts during peaks detection by means of fast GC technique. As a direct consequence, this innovative configuration provided by the use of Micro-Electro-Mechanical-Systems (MEMS) technological processes, ensures the fabrication of extremely-low-volume TCDs, which makes them suitable for applications like fast-GC, where very low dead volumes are required to prevent unwanted phenomena like extra-column band broadening.