An upstream portion of a flow path is stored in a cell block. A filament for detecting thermal conductivity of a sample gas is stored in the upstream portion. The sample gas is led to a downstream portion of an exhaust pipe path through the flow path. The flow path is kept warm by a temperature retainer such that the temperature of the sample gas that passes through the exhaust pipe path does not decrease to a temperature equal to or lower than a liquefaction temperature of the sample gas. Alternatively, at least one portion including a downstream end of the exhaust pipe path is provided to be attachable to and detachable from another portion of the flow path.

An upstream portion of a flow path is stored in a cell block. A filament for detecting thermal conductivity of a sample gas is stored in the upstream portion. The sample gas is led to a downstream portion of an exhaust pipe path through the flow path. The flow path is kept warm by a temperature retainer such that the temperature of the sample gas that passes through the exhaust pipe path does not decrease to a temperature equal to or lower than a liquefaction temperature of the sample gas. Alternatively, at least one portion including a downstream end of the exhaust pipe path is provided to be attachable to and detachable from another portion of the flow path.

A gas chromatograph is provided which is capable of effectively reducing the amount consumed of a carrier gas, reducing the time and effort required for an operator to manually set parameters, and preventing damages to a column and a detector due to a setting mistake. In a case where a stop operation for the power supply of the gas chromatograph is performed (Yes in step S101), the flow rate of a carrier gas to be supplied to a sample vaporization chamber is decreased and the temperatures of the column and the detector are sufficiently lowered (steps S102 to S104), and then the power supply of the gas chromatograph is switched over from an ON state to an OFF state (step S106).

An analysis system for analysing the constituents of a sample of material is provided. A reference supply conduit supplies a source of a first gas. A carrier supply conduit supplies a source of the first or a second gas. First and second reactors are included. A first auto-sampler provides one or more samples of material, the first auto-sampler having an inlet for receiving gas and an outlet for providing the received gas and a sample to the first reactor. A second auto-sampler provides one or more samples of material, the second auto-sampler having an inlet for receiving gas and an outlet for providing the received gas and a sample to the second reactor. A thermal conductivity detector has first and second channels for identifying the relative conductivity of the gases in each channel. A valve system controls the flow of gas from the supply conduits to the auto-samplers.

An analysis system for analysing the constituents of a sample of material is provided. A reference supply conduit supplies a source of a first gas. A carrier supply conduit supplies a source of the first or a second gas. First and second reactors are included. A first auto-sampler provides one or more samples of material, the first auto-sampler having an inlet for receiving gas and an outlet for providing the received gas and a sample to the first reactor. A second auto-sampler provides one or more samples of material, the second auto-sampler having an inlet for receiving gas and an outlet for providing the received gas and a sample to the second reactor. A thermal conductivity detector has first and second channels for identifying the relative conductivity of the gases in each channel. A valve system controls the flow of gas from the supply conduits to the auto-samplers.

Method of fabricating a microelectromechanical structure et comprising two elements suspended from a support, a cavity made in the support, said cavity having two different depths, including: fabrication of a mask on an element comprising a substrate and a structured layer formed on the substrate, said structured layer comprising the two elements that will be suspended above the cavity, the mask being formed above the structured layer, said mask comprising openings with different sections, the openings being distributed in two zones, each zone comprising openings with the same section, anisotropic etching of the element so as to define the two depths under the two suspended elements in the substrate through the structured layer, isotropic etching of the element so as to make the cavity under the suspended elements.

Method of fabricating a microelectromechanical structure et comprising two elements suspended from a support, a cavity made in the support, said cavity having two different depths, including: fabrication of a mask on an element comprising a substrate and a structured layer formed on the substrate, said structured layer comprising the two elements that will be suspended above the cavity, the mask being formed above the structured layer, said mask comprising openings with different sections, the openings being distributed in two zones, each zone comprising openings with the same section, anisotropic etching of the element so as to define the two depths under the two suspended elements in the substrate through the structured layer, isotropic etching of the element so as to make the cavity under the suspended elements.

Disclosed is a micro gas chromatography system including a fluid feeder for feeding a fluid composed of a carrier gas and a gas mixture containing an analyte component to the next stage, a micro gas preconcentrator chip configured to concentrate and desorb the analyte component contained in the fluid, a micro gas chromatography chip including a micro separation column for separating the analyte component concentrated and desorbed by the micro gas preconcentrator chip, and a micro sensing unit including a micro thermal conductivity detection sensor configured to detect the analyte component separated by the micro gas chromatography chip.

Disclosed is a micro gas chromatography system including a fluid feeder for feeding a fluid composed of a carrier gas and a gas mixture containing an analyte component to the next stage, a micro gas preconcentrator chip configured to concentrate and desorb the analyte component contained in the fluid, a micro gas chromatography chip including a micro separation column for separating the analyte component concentrated and desorbed by the micro gas preconcentrator chip, and a micro sensing unit including a micro thermal conductivity detection sensor configured to detect the analyte component separated by the micro gas chromatography chip.

Provided herein are calibration valves that can be used to direct the flow of gases within a gas chromatograph (GC) equipped with a thermal conductivity detector (TCD). The calibration valves can provide both gas calibration and flow control to a GC TCD in a single compact design. For example, the calibration valves can serially deliver a series of small, predetermined volumes of a gas of interest to a GC TCD to facilitate calibration of the GC TCD for detection and/or quantification of the gas of interest in a sample. In certain aspects, the calibration valve can be designed to calibrate the GC TCD with small volumes of a gas of interest (e.g., hydrogen) ranging from 5 mm.sup.3 to 100 mm.sup.3 with high precision. Such a calibration valve can be used to calibrate a GC TCD to detect and/or quantify the gas of interest in a sample.