Abstract: 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), 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.

Abstract: 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.

Abstract: A method for analyzing a gas mixture through gas chromatography, wherein a sample of the gas mixture is fed to a dosing volume using a metering valve in a first valve position and, in a second valve position the sample of the gas mixture is fed from the dosing volume through a separating device by a carrier gas. A gas component of interest, arriving at the separating device and separated from the sample, is detected by a detecting device. Part of the separating device and the metering valve are flushed with another carrier gas after the gas component of interest has passed through a part of the separating device to facilitate a precise gas chromatography analysis using minimal technical effort. Another gas sample is then fed from the dosing volume to the separating device using the other carrier gas.

Abstract: 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.

Abstract: A gas chromatograph for analyzing natural gas, with a first separation column (6). A first detector (7) 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 (8) and a second detector (9) following it are provided to separate or detect carbon dioxide and ethane. A third separation column (10) and a third detector (11) following it are provided to separate or detect nitrogen and methane. A controllable changeover device (12) is provided between the second separation column (8) and the third separation column (10) to discharge eluates following methane. The first, second and third separation columns (6, 8, 10) and the first, second and third detectors (7, 9, 11) are connected in series. At least the first and the second detectors (7, 9) are operable to detect a mixture of substances flowing through them in a non-destructive manner.

Abstract: A thermal conductivity detector with an electrically heatable heating filament (6) that is mounted in the middle of a channel (5) 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 (7, 8) that intersect this channel. In particular to prevent the heating filament from relaxing at operational temperatures, at least one of the two carriers (7, 8) 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 (9). As a result, as the temperature rises, the middle areas of the two carriers (7, 8) on which the heating filament (6) is held move away from each other, so that the heating filament (6) is tightened.

Abstract: A thermal conductivity detector with an electrically heatable heating filament (6) that is mounted in the middle of a channel (5) 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 (7, 8) that intersect this channel. In particular to prevent the heating filament from relaxing at operational temperatures, at least one of the two carriers (7, 8) 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 (9). As a result, as the temperature rises, the middle areas of the two carriers (7, 8) on which the heating filament (6) is held move away from each other, so that the heating filament (6) is tightened.

Abstract: 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.

Abstract: 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 (9, 10), which are positioned on top of one another and joined together. The two plates (9, 10) have congruent channels (11) on their respective sides that face one another. These channels (11) have semicircular cross sections and form gas passages (4 to 8). In addition, at their lateral exit points from the plates (9, 10), the channels (11) form connecting points (12 to 17).

Abstract: 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 (9, 10), which are positioned on top of one another and joined together. The two plates (9, 10) have congruent channels (11) on their respective sides that face one another. These channels (11) have semicircular cross sections and form gas passages (4 to 8). In addition, at their lateral exit points from the plates (9, 10), the channels (11) form connecting points (12 to 17).