Siemens Aktiengesellschaft

Udo Gellert

Glen Eugene Schmidt

Arno Steckenborn

Friedhelm Mueller

Aosheng Wang

Frank Probst

Friedhelm Müller

Friedhelm M&uuml;ller

A multi-way valve has an upper part, a lower part and a central part connected to the upper part via an interposing first membrane and the lower part via an interposing second membrane, wherein the upper and lower parts contain recesses on the upper and lower part faces facing the membranes, where a control fluid is introducible into the recesses, the central part contains a pair of openings in regions opposite the recesses on the central part faces lying adjacent to the membranes, where while introducing the control fluid into a recess, the membrane closes respective opposite openings in the central part, and where the membrane otherwise recedes into the recess, thereby releasing the opposite openings, where valve connections are mounted on the upper or lower part such that the central part can have a very thin design while preventing dead regions in the channel systems.

Multi-way valve

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.

Method and thermal conductivity detector

A thermal conductivity detector for a gas chromatograph includes a heatable resistive detector element configured to be physically arranged in a flow of analytes eluting from a chromatography column and electrically arranged together with resistors in separate arms of a measuring bridge, wherein to provide a new configuration of the thermal conductivity detector to allow high detector sensitivity and to meet intrinsic safety requirements, the detector element includes at least two equal detector sub-elements that are configured to be physically arranged in series in the flow of analytes and electrically arranged in parallel with each other, where the detector element in one arm and a reference resistor in the other arm of the same half of the measuring bridge are configured such that the total resistance of the parallel detector sub-elements at operating temperature is at least approximately equal to the resistance of the reference resistor.

Thermal conductivity detector and detector module

A thermal conductivity detector includes a switch controllable to short-circuit the input of an amplifier to improve the thermal conductivity detector for use in gas chromatography without the need of an additional reference cell, wherein a digital signal processor calculates a transfer function of an analog signal processor from a digitized difference signal received in response to short-circuiting the input of the amplifier at a given time when solely a reference carrier fluid passes through a measuring cell, and the digital signal processor recovers a detector signal by deconvoluting the digitized difference signal with a transfer function.

Thermal conductivity detector circuit and method for operating the same

A modulator for simply providing fast and precise sampling of a chromatographic peak eluting from a first column into a second column of a comprehensive two-dimensional gas chromatograph, where the modulator includes a planar component containing a first gas passage for connecting a carrier gas source to the second separation column, a second gas passage for connecting the first separation column to an exhaust outlet, a connecting gas passage between the first and second gas passages, and two individually controllable open/close valves arranged in parallel connection in the first gas passage between its connection to the carrier gas source and the branch-off of the connecting gas passage, and where the gas passages and valves are formed in the planar component by micromachining.

Comprehensive two-dimensional gas chromatograph and modulator for the chromatograph

A thermal conductivity detector includes at least four detector components that are arranged in receptacles of a thermal conduction block in a circle around a center axis of the thermal conduction block. The thermal conduction block comprises a central portion along the axis, the cross-axial dimensions of the central portion being less than the diameter of the circle. There are at least four equal peripheral portions that are connected solely to the central portion and are separated from each other, each of the peripheral portions carrying one of the detector components.

Thermal conductivity detector

A method for improving the chromatographic detection limit for an analyte including a) producing a chromatogram with a peak of the analyte, b) calculating a regression straight line for a baseline from measured values of a section without a peak in the chromatogram, c) calculating a regression function from measured values of the peak of the analyte, d) subtracting the regression function from the chromatogram, e) calculating a regression polynomial for the baseline from the values of the chromatogram which have been changed in step d), f) calculating a further regression function from the measured values of the peak in the produced chromatogram, g) calculating a peak area between the regression polynomial and the further regression function, h) repetition of step d) with the further regression function instead of the regression function and of steps e), f) and g), until the calculated peak area changes by less than a predetermined amount.

Method for improving a chromatographic detection limit for an analyte

The invention relates to a gas sample to be analyzed, wherein said sample is guided by means of a carrier gas through a separator unit having a downstream thermal conductivity detector providing a chromatogram having peaks for different analytes as a measurement signal. When using a thermal conductivity detector having a heated gold thread coated with a parylene F, hydrogen is used as a carrier gas, and a peak for the analyte hydrogen sulfide is generated by differentiating the chromatogram at the location of said analyte. The invention permits unlimited use of hydrogen as a carrier gas, even if the analyte is oxygen.

Method and arrangement for gas chromatographic analysis of a gas sample

A liquid-metering device comprising a droplet generator including a reservoir and, connected to the latter, a displacement space which is modifiable by an electromechanical transducer and which has an outlet opening and, upon excitation of the transducer, shoots a liquid droplet from a cold area into a heatable area through or counter to a gas stream generated by a gas source. To make the device suitable for automatic and quasi-continuous liquid metering in process analysis, a heatable evaporation chamber is provided through which the liquid to be metered flows via valves, and, between the evaporation chamber and the reservoir, a condensate chamber is connected via further valves. The condensate chamber and the reservoir are connected via additional valves and a pressure regulator to the gas source.

Liquid-metering device for a gas analyzer

A gas chromatograph for analyzing natural gas, with a first separation column (). A first detector () is provided following the first separation column, the first separation column and the first detector operable to separate or detect propane and higher hydrocarbons. A second separation column () and a second detector () following it are provided to separate or detect carbon dioxide and ethane. A third separation column () and a third detector () following it are provided to separate or detect nitrogen and methane. A controllable changeover device () is provided between the second separation column () and the third separation column () to discharge eluates following methane. The first, second and third separation columns () and the first, second and third detectors () are connected in series. At least the first and the second detectors () are operable to detect a mixture of substances flowing through them in a non-destructive manner.

Gas chromatograph and method for analyzing a mixture of substances by gas chromatography

An arrangement for metering a gaseous sample in a carrier gas stream has a sample gas path and a carrier gas path, both paths being connected to a carrier gas source. By introducing different pressures into the sample gas path and the carrier gas path, a metered amount is extracted from a sample slug and diverted into the carrier gas stream via a connection gas path through the carrier gas path. The sample gas path has two flow resistances in front of and behind a branch point of a connection gas path. One resistance lies between the carrier gas source and a metering unit and a gas volume of the sample gas path between the branch point of the connection gas path and the other flow resistance is dimensioned such that the sample slug only reaches the second resistance after extraction and diversion of the metered amount.

Arrangement for metering a gaseous sample in a carrier gas stream

A thermal conductivity detector with an electrically heatable heating filament () that is mounted in the middle of a channel () in such a way that a fluid can flow around it. The heating filament is carried on its two ends on two electrically conductive carriers () that intersect this channel. In particular to prevent the heating filament from relaxing at operational temperatures, at least one of the two carriers () is embodied in such a way that its distance from the other carrier is greater in the region of the middle of the channel than in the region of the wall of the channel (). As a result, as the temperature rises, the middle areas of the two carriers () on which the heating filament () is held move away from each other, so that the heating filament () is tightened.

Heat conductivity detector

A separation-column unit includes a support plate having a groove formed therein on one side and running, for example, in the form of a spiral, and having a cover plate which bears against this side. In order to achieve the high separation capacity combined with a high load-bearing capacity with regard to the amount of sample flowing through, the depth (d) of the groove is preferably at least three times greater than its width. The base of the groove preferably has a rounded cross section, it being possible for the cover plate to contain a corresponding channel.

Separation-column unit for a gas-chromatograph and method for making the same

To switch gas flows between gas sources and gas sinks, a gas flow switching device includes gas passages, which communicate with one another and which have connecting points for the gas sources and the gas sinks. Furthermore, the gas flow switching device has a device for setting different pressures. To simplify the construction of the gas flow switching device and to achieve precisely defined pressure and flow conditions without the need for calibration, the gas flow switching device has two plates ( ), which are positioned on top of one another and joined together. The two plates ( ) have congruent channels ( ) on their respective sides that face one another. These channels ( ) have semicircular cross sections and form gas passages ( to ). In addition, at their lateral exit points from the plates ( ), the channels ( ) form connecting points ( to ).

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Bellheim, Germany

Udo Gellert