US20010027722A1 - Method and apparatus for gas chromatography analysis of samples - Google Patents
Method and apparatus for gas chromatography analysis of samples Download PDFInfo
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- US20010027722A1 US20010027722A1 US09/738,543 US73854300A US2001027722A1 US 20010027722 A1 US20010027722 A1 US 20010027722A1 US 73854300 A US73854300 A US 73854300A US 2001027722 A1 US2001027722 A1 US 2001027722A1
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/04—Preparation or injection of sample to be analysed
- G01N30/06—Preparation
- G01N30/14—Preparation by elimination of some components
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/26—Conditioning of the fluid carrier; Flow patterns
- G01N30/38—Flow patterns
- G01N30/46—Flow patterns using more than one column
- G01N30/468—Flow patterns using more than one column involving switching between different column configurations
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/04—Preparation or injection of sample to be analysed
- G01N30/06—Preparation
- G01N30/12—Preparation by evaporation
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/04—Preparation or injection of sample to be analysed
- G01N30/06—Preparation
- G01N30/12—Preparation by evaporation
- G01N2030/121—Preparation by evaporation cooling; cold traps
- G01N2030/122—Preparation by evaporation cooling; cold traps cryogenic focusing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/04—Preparation or injection of sample to be analysed
- G01N30/06—Preparation
- G01N30/12—Preparation by evaporation
- G01N2030/126—Preparation by evaporation evaporating sample
- G01N2030/128—Thermal desorption analysis
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/04—Preparation or injection of sample to be analysed
- G01N30/06—Preparation
- G01N30/14—Preparation by elimination of some components
- G01N2030/143—Preparation by elimination of some components selective absorption
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/26—Conditioning of the fluid carrier; Flow patterns
- G01N30/38—Flow patterns
- G01N2030/382—Flow patterns flow switching in a single column
- G01N2030/383—Flow patterns flow switching in a single column by using auxiliary fluid
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/26—Conditioning of the fluid carrier; Flow patterns
- G01N30/38—Flow patterns
- G01N30/46—Flow patterns using more than one column
- G01N30/461—Flow patterns using more than one column with serial coupling of separation columns
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N30/00—Investigating or analysing materials by separation into components using adsorption, absorption or similar phenomena or using ion-exchange, e.g. chromatography or field flow fractionation
- G01N30/02—Column chromatography
- G01N30/26—Conditioning of the fluid carrier; Flow patterns
- G01N30/38—Flow patterns
- G01N30/46—Flow patterns using more than one column
- G01N30/466—Flow patterns using more than one column with separation columns in parallel
Definitions
- the invention relates to a method and apparatus for gas chromatography analysis of samples.
- thermodesorption analysis of a sample after preceding thermodesorption in which the components to be separated and water are contained, is provided,
- thermodesorbed sample is transferred by means of carrier gas into a first polar separation column which retains higher-boiling components and water and passes low-boiling components
- said low boiling components being led, past a branching device which leads, on the one hand, to a second polar or non-polar separation column and, on the other hand, to a non-polar separation column, to the non-polar separation column in a fashion excluding access to the second polar or non-polar separation column,
- an apparatus for gas chromatography analysis of a sample comprising:
- thermodesorption device for holding a sampling tube
- thermodesorption device a first polar separation column being connected downstream of the thermodesorption device
- a branching device being connected downstream of the first polar separation column
- a second separation column being of the group of a polar and a non-polar separation column
- branching device being switchable over between said non-polar separation column
- the low-boiling components are separated on the non-polar separation column via a pneumatically closeable bifurcation which leads, on the one hand, to a non-polar separation column for gases and, on the other hand, via a cryofocussing device, to a further polar or non-polar separation column, whereupon after pneumatically switching over the bifurcation the water with higher-boiling components is eliminated in the region of the cryofocussing device, whereupon the higher-boiling components are separated in the polar or non-polar separation column downstream of the cryofocussing device.
- the water elimination with subsequent separation and analysis of a sample, and the separation on the further separation column with subsequent analysis of another sample can be carried out simultaneously.
- FIG. 1 shows a diagram of a gas chromatography apparatus according to the invention, partially in section.
- FIG. 2 shows the diagrammatic design of an embodiment of a thermodesorption device or cryofocussing device or a device for eliminating water for the gas chromatography device of FIG. 1, in section.
- FIG. 3 shows a diagram of a design of a branching point for the gas chromatography device of FIG. 1, in section.
- the gas chromatography apparatus illustrated in FIG. 1 comprises a thermodesorption device 1 for a sample contained in a sampling tube 2 , a carrier gas connection 3 and a gas exhaust line 4 being provided.
- a transfer capillary 7 leading from the thermodesorption device 1 to a feed head 5 of a cryofocussing device 6 can be heated by a transfer furnace 8 in order to avoid material losses upon transfer from the sampling tube 2 to the cryofocussing device 6 .
- the cryofocussing device 6 comprises a gas exhaust line 9 .
- a transfer capillary 10 a, 10 b downstream of the cryofocussing device 6 leads, if appropriate, via a switchover valve 11 to a column collecting piece 12 of a polar separation column 13 serving as capillary precolumn, the column connecting piece 12 comprising a gas exhaust line 14 .
- the switchover valve 11 also comprises several feed or discharge lines 11 a - 11 d for flushing, calibration or automatic sampling.
- the transfer capillary 10 a, 10 b is arranged in a transfer furnace 15 which can, if appropriate, form a common furnace with the transfer furnace 8 .
- a branching device 16 is arranged at the end downstream of the polar separation column 13 , which exhibits stable properties with regard to separation in the presence of water. Separation columns 17 , 18 are connected separately from one another to the branching device 16 , it being possible to exclude pneumatically the access to in each case one of the separation columns 17 , 18 via a gas line 19 , which can be charged with gas via a valve 20 or 21 and a controller 22 .
- the separation column 17 is a non-polar separation column which, in particular, operates according to the principle of a micropacked column, and serves to separate low-boiling components.
- the separation column 17 is connected to an analyzer A 1 .
- the separation column 18 is a polar or non-polar separation column with stable properties with regard to the separation of polar components.
- the separation column 18 is connected to an analyser A 2 .
- a device 23 for eliminating water which comprises a carrier gas connection 24 and a gas exhaust line 25 for the purpose of eliminating interfering water.
- a thermal conductivity detector 26 connected to the gas exhaust line 25 is used to monitor the completeness of the elimination.
- the polar separation column 13 can be arranged in a furnace 27 which can, if appropriate, form a single furnace with the transfer furnace 8 .
- the capillary separation columns 17 , 18 are preferably arranged in the furnaces 28 and 29 , respectively, but they can also be arranged in a common furnace, if appropriate together with the polar separation column 13 .
- the device 23 illustrated in FIG. 2, for eliminating water comprises a cooling device, which can be formed by a Peltier element, a cyrostat or a passage for liquefied gas such as liquid nitrogen.
- a housing casing 30 is provided with coolant bores 31 which can be connected to a coolant source, the housing casing 30 accommodating a metal tube 33 which is surrounded by a heating winding 32 and for its part accommodates the sampling tube 2 .
- An annular gap 34 which is connected to the gas exhaust line 25 is located between the metal tube 33 and the sampling tube 2 .
- the carrier gas connection 24 opens into the sampling tube 2 in the region of a feed head 35 .
- the separation column 18 is plugged into the device 23 for eliminating water in such a way that it projects into the sampling tube 2 . Since the inside diameter of the sampling tube 2 is larger than the outside diameter of the separation column 18 , the interior of the sampling tube 2 is also connected to the annular gap 34 .
- thermodesorption device 1 and the cryofocussing device 6 can be designed in a fashion corresponding to the device 23 for eliminating water, and so reference is made to FIG. 2 in each case in connection with these devices.
- the design can be selected, for example, to accord with DE 44 19 596 C1, but it is also possible here to provide cooling by a Peltier element or a cryostat, while consideration may be given respectively in this connection to a heating cartridge for example in accordance with DE 198 17 017 A1.
- the annular gap 34 and the gas exhaust line 4 or 9 can be dispensed with, if appropriate, in the case of the thermodesorption device 1 and the cryofocussing device 6 when split-mode operation is not desired.
- thermodesorption device 1 can be designed as in the case where sampling tubes 2 are to be used such as described, for example, in DE 195 20 715 C1.
- DE 44 19 596 C1, DE 198 17 017 A1, and DE 195 20 715 C1 is incorporated herein by reference, as are any English-language equivalents thereof.
- a central branching piece 36 is connected to two further branching pieces 37 , 38 via capillary adapters 39 which, for their part, are connected via the valve 20 or 21 and the controller 22 to the gas line 19 or to the separation column 17 or 18 , it being possible, if appropriate, to connect the central branching piece 36 to a monitor detector 40 , in particular a thermal conductivity detector.
- thermodesorption device 1 A sample contained in the sampling tube 2 is thermodesorbed in the thermodesorption device 1 by controlled heating of the sampling tube 2 by means of the heating winding 32 .
- carrier gas is fed into the sampling tube 2 via the carrier gas connection 3 , and led into the cryofocussing device 6 via the heated transfer capillary 7 for the purpose of transporting desorbed substances, including water which is present.
- Uniform feeding of carrier gas is maintained constant in this case in each method step via a flow sensor with a controller. Since thermodesorption is performed without splitting, the gas exhaust line 4 remains closed and thereby pneumatically closes the access to the annular gap 34 .
- the cryofocussing device 6 is closed off at the end, if appropriate by means of the switchover valve 11 , from the column connecting piece 12 , its gas exhaust line 9 is opened, for example via a valve (not illustrated), and its sampling tube 2 is cooled down to minus 150° C. by appropriate cooling, for example with liquid nitrogen, such that all the components of the sample which are to be investigated, including the water contained, are collected in the sampling tube 2 and thus enriched.
- the gas exhaust line 9 is closed, while the sampling tube 2 is heated up, while being monitored, to a temperature of, for example, 350° C., by means of the heating winding 32 , all the enriched components leaving the sampling tube 2 of the cryofocussing device 6 and now being led into the separation column 13 by means of carrier gas because of the open switchover valve 11 via the column connecting piece 12 .
- the preliminary separation into two fractions of the separation column 13 is initially not influenced by water which is present, and higher-boiling components and water are retained there by interaction forces of different strength for a longer time than low-boiling, essentially non-polar components.
- the low-boiling non-polar components i.e. those with one to approximately four or more carbon atoms
- the valve 20 is opened in this case, and so the branching device 16 is pneumatically closed towards the polar or non-polar separation column 18 , and the low-boiling non-polar components are permitted to pass to the non-polar separation column 17 by means of a controlled carrier gas flow.
- These components are separated in the non-polar separation column 17 and analyzed in the analyzer A 1 .
- valve 20 In a second phase of the separation by the polar separation column 13 , the valve 20 is closed and the valve 21 is opened such that the branching device 16 is now pneumatically closed off from the non-polar separation column 17 .
- the valves 20 , 21 are switched over in principle as a function of time, the switch over being calibrated to a retention time of a specific compound, which is low boiling by comparison with water, in the non-polar separation column 17 , for example to the retention time of toluene, but it can also be performed earlier, if appropriate, when the monitor detector 40 which reacts to water outputs a signal on the basis of incoming water which has the effect of permitting access by higher-boiling components and water on the basis of the now reversed direction of the overall gas flow to the polar separation column 18 via the device 33 for eliminating water, the polar separation column 13 then being additionally heated via the furnace 27 in order to release all higher-boiling components and/or water.
- the device 23 for eliminating water permits higher-boiling components to be separated from water in three phases.
- a first phase the cryofocussing, the higher-boiling components and water are collected and enriched—as in the case of enrichment in the cryofocussing device 6 .
- the sampling tube 2 of the device 23 for eliminating water is heated by means of its heating winding 32 , the water being eliminated via the open gas exhaust line 25 .
- This heating is performed to a temperature above the freezing point of water and below the boiling point of water, preferably to a relatively low temperature of, for example, 10 to 20 20 C., this temperature being selected in such a way that as little loss of components as possible results in this case, but an adequate water vapor partial pressure is present.
- the monitoring of the water content in the sample is performed in this case by means of the thermal conductivity detector 26 , which reacts to the presence of water and is connected to the gas exhaust line 25 .
- the gas exhaust line 25 is closed on the basis of a signal output by the thermal conductivity detector 26 , whereupon in the third phase the sampling tube 2 of the device 23 for eliminating water is heated further in a programmed fashion by means of the heating winding 32 , and the individual components are released again one after another and are then led into the polar or non-polar separation column 18 in which they are successively separated and analyzed in the analyzer A 2 .
- the sample prefferably be introduced quickly in the column connecting piece 12 on the basis of operation as a consequence of a continuously open gas exhaust line 14 by means of the flow velocity, thereby increased, in order in this way to achieve a defined peak end (avoidance of peak tailing) with a defined sharpness of separation. Thinning of the sample resulting therefrom is generally acceptable.
- a sample can be introduced into the thermodesorption device 1 by means of an exchangeable sampling tube 2 .
- the sample can, however, also be collected in the sampling tube 2 of the thermodesorption device 1 by the sucked-in ambient atmosphere during split-mode operation with the gas exhaust line 9 open, the gas being eliminated via the annular gap 34 and the gas exhaust line 9 .
- the switchover valve 11 can, also be arranged upstream of the cryofocussing device 6 in the region of the transfer capillary 7 .
- the switchover valve 11 is adjusted after a passage of the sample in such a way that firstly, with the aid of the now connected feed line 11 a and 11 b the sample inlet is flushed up to the outlet, and secondly, with the aid of the likewise connected transfer capillary 10 a, the feed line 11 a and 11 b, and also the connected feed line to the carrier gas connection 3 , the thermodesorption device 1 and the cryofocussing device 6 are flushed, while because of the closed exhaust line 14 the sample is led further to the column interface 12 via the polar separation column 13 . Consequently, on the basis of the above circuit it is possible to take a new sample in parallel with the sample to be analyzed or to carry out a calibration of the thermodesorption device 1 and of the cryofocussing device 6 .
- the separation columns 13 , 17 and 18 are likewise arranged in individual furnaces 27 , 28 and 29 such that after passage of the respective sample the separation columns 13 , 17 , 18 are cooled down individually and prepared for the subsequent sample, the temperature intervals being selected to be smaller by the furnace 27 , 28 , 29 , which is to be assigned respectively to only one separation column 13 , 17 , 18 , and cooling taking place more quickly.
- the pneumatic exclusion from the polar or non-polar separation column 18 via the device 23 for eliminating water, or from the non-polar separation column 17 is achieved on the basis of switching over the valves 20 , 21 and on the basis of the controller 22 , which sets a higher flow velocity of the gas from the gas line 19 than is prescribed by the carrier gas flow which flows through the polar separation column 13 .
- the capillary adapters 39 which have a diameter of 50 ⁇ m to 100 ⁇ m, for example, are to be dimensioned in this case in terms of length and diameter and as a function of the gas pressure used in such a way that no diffusion takes place from the central branching piece 36 up to that one of the two branching pieces 37 , 38 which leads to the separation column 17 , 18 respectively not to be used.
Abstract
Description
- The invention relates to a method and apparatus for gas chromatography analysis of samples.
- To use gas chromatography to investigate small quantities of components present in gases or liquids, such as foreign substances or pollutants or impurities, it is known firstly to enrich these in order then to feed them into a gas chromatograph via an appropriate feeding system. However, problems occur in this case when the collected samples contain moisture such as is the case, for example, when pollutants contained in the air are enriched, since the moisture contained in the air is then also enriched.
- However, water severely disturbs a gas chromatography system, and likewise the analysis, in the case of which, for example, a substantial loss in sensitivity occurs in the mass spectrometer. The presence of water in separation columns alters the retention time, doing so, specifically, as a function of quantity and differently for different substances, thus creating the need to eliminate this as completely as possible in order to obtain reliable measurement results.
- It is known to eliminate the moisture which is present in samples to be chromatographically analyzed by osmosis. However, this has the disadvantage that polar components are also eliminated in the process, while non-polar components remain essentially uninfluenced. However, the elimination of polar components other than water falsifies the chromatogram.
- Also known are packed capillary columns which exhibit a temperature-dependent adsorptivity with reference to water, so that given appropriate setting, low-boiling components are passed while higher-boiling components and water are retained.
- It is an object of the invention to provide a method for gas chromatography analysis of samples which permits reliable gas chromatograms to be obtained from samples containing water.
- It is a further object of the invention to provide an apparatus for gas chromatography analysis of samples which permits reliable gas chromatograms to be obtained from samples containing water.
- According to the invention a method for gas chromatography analysis of a sample after preceding thermodesorption, in which the components to be separated and water are contained, is provided,
- wherein the thermodesorbed sample is transferred by means of carrier gas into a first polar separation column which retains higher-boiling components and water and passes low-boiling components,
- said low boiling components being led, past a branching device which leads, on the one hand, to a second polar or non-polar separation column and, on the other hand, to a non-polar separation column, to the non-polar separation column in a fashion excluding access to the second polar or non-polar separation column,
- after which the higher-boiling components and the water are lead to the second polar or non-polar separation column in a manner excluding access to the non-polar separation column,
- the water being eliminated upstream of the second polar or non-polar separation column by means of cryofocussing.
- According to the invention, further an apparatus for gas chromatography analysis of a sample is provided, comprising:
- a thermodesorption device for holding a sampling tube;
- a first polar separation column being connected downstream of the thermodesorption device;
- a branching device being connected downstream of the first polar separation column;
- a non-polar separation column;
- a second separation column being of the group of a polar and a non-polar separation column;
- wherein said branching device being switchable over between said non-polar separation column; and
- a device for eliminating water which is connected upstream of the second separation column.
- By virtue of the fact that according to the present invention use is made as a precolumn of a polar separation column with a stationary phase, which water does not initially have the effect of separating it preliminarily into two fractions, higher-boiling components and water can be retained at the beginning, while low-boiling components are passed. The low-boiling components are separated on the non-polar separation column via a pneumatically closeable bifurcation which leads, on the one hand, to a non-polar separation column for gases and, on the other hand, via a cryofocussing device, to a further polar or non-polar separation column, whereupon after pneumatically switching over the bifurcation the water with higher-boiling components is eliminated in the region of the cryofocussing device, whereupon the higher-boiling components are separated in the polar or non-polar separation column downstream of the cryofocussing device. In addition, in this case the water elimination with subsequent separation and analysis of a sample, and the separation on the further separation column with subsequent analysis of another sample, can be carried out simultaneously.
- In this case, not only gaseous but also liquid samples which contain water can be taken automatically by means of the apparatus.
- Further objects, embodiments and advantages of the invention will become apparent from the following description and the claims.
- The invention is explained below in more detail with reference to a preferred embodiment illustrated schematically in the attached illustrations.
- FIG. 1 shows a diagram of a gas chromatography apparatus according to the invention, partially in section.
- FIG. 2 shows the diagrammatic design of an embodiment of a thermodesorption device or cryofocussing device or a device for eliminating water for the gas chromatography device of FIG. 1, in section.
- FIG. 3 shows a diagram of a design of a branching point for the gas chromatography device of FIG. 1, in section.
- The gas chromatography apparatus illustrated in FIG. 1 comprises a thermodesorption device1 for a sample contained in a
sampling tube 2, acarrier gas connection 3 and agas exhaust line 4 being provided. Atransfer capillary 7 leading from the thermodesorption device 1 to afeed head 5 of acryofocussing device 6 can be heated by atransfer furnace 8 in order to avoid material losses upon transfer from thesampling tube 2 to thecryofocussing device 6. Thecryofocussing device 6 comprises a gas exhaust line 9. Atransfer capillary cryofocussing device 6 leads, if appropriate, via a switchover valve 11 to acolumn collecting piece 12 of apolar separation column 13 serving as capillary precolumn, thecolumn connecting piece 12 comprising a gas exhaust line 14. The switchover valve 11 also comprises several feed or discharge lines 11 a-11 d for flushing, calibration or automatic sampling. Thetransfer capillary transfer furnace 15 which can, if appropriate, form a common furnace with thetransfer furnace 8. - A
branching device 16 is arranged at the end downstream of thepolar separation column 13, which exhibits stable properties with regard to separation in the presence of water.Separation columns 17, 18 are connected separately from one another to thebranching device 16, it being possible to exclude pneumatically the access to in each case one of theseparation columns 17, 18 via agas line 19, which can be charged with gas via avalve 20 or 21 and acontroller 22. - The separation column17 is a non-polar separation column which, in particular, operates according to the principle of a micropacked column, and serves to separate low-boiling components. The separation column 17 is connected to an analyzer A1.
- The
separation column 18 is a polar or non-polar separation column with stable properties with regard to the separation of polar components. Theseparation column 18 is connected to an analyser A2. Connected upstream of theseparation column 18 is adevice 23 for eliminating water, which comprises acarrier gas connection 24 and agas exhaust line 25 for the purpose of eliminating interfering water. In this case, athermal conductivity detector 26 connected to thegas exhaust line 25 is used to monitor the completeness of the elimination. - The
polar separation column 13 can be arranged in afurnace 27 which can, if appropriate, form a single furnace with thetransfer furnace 8. - The
capillary separation columns 17, 18 are preferably arranged in thefurnaces polar separation column 13. - The
device 23, illustrated in FIG. 2, for eliminating water comprises a cooling device, which can be formed by a Peltier element, a cyrostat or a passage for liquefied gas such as liquid nitrogen. In the exemplary embodiment illustrated, ahousing casing 30 is provided withcoolant bores 31 which can be connected to a coolant source, thehousing casing 30 accommodating ametal tube 33 which is surrounded by a heating winding 32 and for its part accommodates thesampling tube 2. Anannular gap 34 which is connected to thegas exhaust line 25 is located between themetal tube 33 and thesampling tube 2. Thecarrier gas connection 24 opens into thesampling tube 2 in the region of afeed head 35. Theseparation column 18 is plugged into thedevice 23 for eliminating water in such a way that it projects into thesampling tube 2. Since the inside diameter of thesampling tube 2 is larger than the outside diameter of theseparation column 18, the interior of thesampling tube 2 is also connected to theannular gap 34. - The thermodesorption device1 and the
cryofocussing device 6 can be designed in a fashion corresponding to thedevice 23 for eliminating water, and so reference is made to FIG. 2 in each case in connection with these devices. The design can be selected, for example, to accord with DE 44 19 596 C1, but it is also possible here to provide cooling by a Peltier element or a cryostat, while consideration may be given respectively in this connection to a heating cartridge for example in accordance with DE 198 17 017 A1. However, if appropriate, theannular gap 34 and thegas exhaust line 4 or 9 can be dispensed with, if appropriate, in the case of the thermodesorption device 1 and thecryofocussing device 6 when split-mode operation is not desired. The thermodesorption device 1 can be designed as in the case wheresampling tubes 2 are to be used such as described, for example, in DE 195 20 715 C1. Each of DE 44 19 596 C1, DE 198 17 017 A1, and DE 195 20 715 C1 is incorporated herein by reference, as are any English-language equivalents thereof. - In the embodiment of the branching
device 16 of FIG. 3, a central branchingpiece 36 is connected to two further branchingpieces 37, 38 viacapillary adapters 39 which, for their part, are connected via thevalve 20 or 21 and thecontroller 22 to thegas line 19 or to theseparation column 17 or 18, it being possible, if appropriate, to connect the central branchingpiece 36 to amonitor detector 40, in particular a thermal conductivity detector. - A sample contained in the
sampling tube 2 is thermodesorbed in the thermodesorption device 1 by controlled heating of thesampling tube 2 by means of the heating winding 32. During thermodesorption, carrier gas is fed into thesampling tube 2 via thecarrier gas connection 3, and led into thecryofocussing device 6 via theheated transfer capillary 7 for the purpose of transporting desorbed substances, including water which is present. Uniform feeding of carrier gas is maintained constant in this case in each method step via a flow sensor with a controller. Since thermodesorption is performed without splitting, thegas exhaust line 4 remains closed and thereby pneumatically closes the access to theannular gap 34. - Initially, the
cryofocussing device 6 is closed off at the end, if appropriate by means of the switchover valve 11, from thecolumn connecting piece 12, its gas exhaust line 9 is opened, for example via a valve (not illustrated), and itssampling tube 2 is cooled down to minus 150° C. by appropriate cooling, for example with liquid nitrogen, such that all the components of the sample which are to be investigated, including the water contained, are collected in thesampling tube 2 and thus enriched. Thereafter, the gas exhaust line 9 is closed, while thesampling tube 2 is heated up, while being monitored, to a temperature of, for example, 350° C., by means of the heating winding 32, all the enriched components leaving thesampling tube 2 of thecryofocussing device 6 and now being led into theseparation column 13 by means of carrier gas because of the open switchover valve 11 via thecolumn connecting piece 12. - The preliminary separation into two fractions of the
separation column 13 is initially not influenced by water which is present, and higher-boiling components and water are retained there by interaction forces of different strength for a longer time than low-boiling, essentially non-polar components. - In the first phase of the separation by the
polar separation column 13 in which thefurnace 27 is at ambient temperature, the low-boiling non-polar components, i.e. those with one to approximately four or more carbon atoms, flow through thepolar separation column 13 virtually without a separation effect, and subsequently through the branchingdevice 16. The valve 20 is opened in this case, and so the branchingdevice 16 is pneumatically closed towards the polar ornon-polar separation column 18, and the low-boiling non-polar components are permitted to pass to the non-polar separation column 17 by means of a controlled carrier gas flow. These components are separated in the non-polar separation column 17 and analyzed in the analyzer A1. - In a second phase of the separation by the
polar separation column 13, the valve 20 is closed and thevalve 21 is opened such that the branchingdevice 16 is now pneumatically closed off from the non-polar separation column 17. Thevalves 20, 21 are switched over in principle as a function of time, the switch over being calibrated to a retention time of a specific compound, which is low boiling by comparison with water, in the non-polar separation column 17, for example to the retention time of toluene, but it can also be performed earlier, if appropriate, when themonitor detector 40 which reacts to water outputs a signal on the basis of incoming water which has the effect of permitting access by higher-boiling components and water on the basis of the now reversed direction of the overall gas flow to thepolar separation column 18 via thedevice 33 for eliminating water, thepolar separation column 13 then being additionally heated via thefurnace 27 in order to release all higher-boiling components and/or water. - The
device 23 for eliminating water permits higher-boiling components to be separated from water in three phases. - In a first phase, the cryofocussing, the higher-boiling components and water are collected and enriched—as in the case of enrichment in the
cryofocussing device 6. In a second phase, thesampling tube 2 of thedevice 23 for eliminating water is heated by means of its heating winding 32, the water being eliminated via the opengas exhaust line 25. This heating is performed to a temperature above the freezing point of water and below the boiling point of water, preferably to a relatively low temperature of, for example, 10 to 2020 C., this temperature being selected in such a way that as little loss of components as possible results in this case, but an adequate water vapor partial pressure is present. The monitoring of the water content in the sample is performed in this case by means of thethermal conductivity detector 26, which reacts to the presence of water and is connected to thegas exhaust line 25. Once the water has been completely eliminated, thegas exhaust line 25 is closed on the basis of a signal output by thethermal conductivity detector 26, whereupon in the third phase thesampling tube 2 of thedevice 23 for eliminating water is heated further in a programmed fashion by means of the heating winding 32, and the individual components are released again one after another and are then led into the polar ornon-polar separation column 18 in which they are successively separated and analyzed in the analyzer A2. - Water is eliminated in the
device 23 for eliminating water by virtue of the fact that itssampling tube 2 is heated by means of the heating winding 32, and that, with thegas exhaust line 25 open, the carrier gas flowing past a fed sample containing water flows to the polar ornon-polar separation column 18 at the end, averted from thefeed head 35, of thesampling tube 2 of thedevice 23 for eliminating water, back to thegas exhaust line 25 through theannular gap 34, and is thereby eliminated. This form of elimination of individual components, also termed split-mode operation, can also take place in thecryofocussing device 6 by means of a gas exhaust line 9, which is open here, and in the thermodesorption device 1 by means of agas exhaust line 4, which is open here. Thegas exhaust lines - It is expedient for the sample to be introduced quickly in the
column connecting piece 12 on the basis of operation as a consequence of a continuously open gas exhaust line 14 by means of the flow velocity, thereby increased, in order in this way to achieve a defined peak end (avoidance of peak tailing) with a defined sharpness of separation. Thinning of the sample resulting therefrom is generally acceptable. - A sample can be introduced into the thermodesorption device1 by means of an
exchangeable sampling tube 2. Instead of this, the sample can, however, also be collected in thesampling tube 2 of the thermodesorption device 1 by the sucked-in ambient atmosphere during split-mode operation with the gas exhaust line 9 open, the gas being eliminated via theannular gap 34 and the gas exhaust line 9. If appropriate, the switchover valve 11 can, also be arranged upstream of thecryofocussing device 6 in the region of thetransfer capillary 7. - The switchover valve11 is adjusted after a passage of the sample in such a way that firstly, with the aid of the now connected feed line 11 a and 11 b the sample inlet is flushed up to the outlet, and secondly, with the aid of the likewise connected
transfer capillary 10 a, the feed line 11 a and 11 b, and also the connected feed line to thecarrier gas connection 3, the thermodesorption device 1 and thecryofocussing device 6 are flushed, while because of the closed exhaust line 14 the sample is led further to thecolumn interface 12 via thepolar separation column 13. Consequently, on the basis of the above circuit it is possible to take a new sample in parallel with the sample to be analyzed or to carry out a calibration of the thermodesorption device 1 and of thecryofocussing device 6. - In a preferred embodiment, the
separation columns individual furnaces separation columns furnace separation column - The pneumatic exclusion from the polar or
non-polar separation column 18 via thedevice 23 for eliminating water, or from the non-polar separation column 17 is achieved on the basis of switching over thevalves 20, 21 and on the basis of thecontroller 22, which sets a higher flow velocity of the gas from thegas line 19 than is prescribed by the carrier gas flow which flows through thepolar separation column 13. Thecapillary adapters 39, which have a diameter of 50 μm to 100 μm, for example, are to be dimensioned in this case in terms of length and diameter and as a function of the gas pressure used in such a way that no diffusion takes place from the central branchingpiece 36 up to that one of the two branchingpieces 37, 38 which leads to theseparation column 17, 18 respectively not to be used. - While the invention has been shown and described with reference to a preferred embodiment, it should be apparent to one of ordinary skill in the art that many changes and modifications may be made without departing from the spirit and scope of the invention as defined in the claims.
Claims (32)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE19960631.5 | 1999-12-16 | ||
DE19960631A DE19960631C1 (en) | 1999-12-16 | 1999-12-16 | Gas chromatographic analysis of sample after thermo-desorption comprises transferring thermo-desorbed sample into first polar separating column |
Publications (2)
Publication Number | Publication Date |
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US20010027722A1 true US20010027722A1 (en) | 2001-10-11 |
US6447575B2 US6447575B2 (en) | 2002-09-10 |
Family
ID=7932842
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US09/738,543 Expired - Lifetime US6447575B2 (en) | 1999-12-16 | 2000-12-15 | Method and apparatus for gas chromatography analysis of samples |
Country Status (5)
Country | Link |
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US (1) | US6447575B2 (en) |
JP (1) | JP3460986B2 (en) |
KR (1) | KR100479596B1 (en) |
AU (1) | AU770281B2 (en) |
DE (1) | DE19960631C1 (en) |
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US20100120161A1 (en) * | 2007-04-26 | 2010-05-13 | Masuo Iida | Method of analyzing inorganic phosphorus in organic material and apparatus therefor |
US9000360B2 (en) | 2010-10-29 | 2015-04-07 | Thermo Fisher Scientific Oy | System layout for an automated system for sample preparation and analysis |
US20180299415A1 (en) * | 2017-04-14 | 2018-10-18 | Entech Instruments Inc. | Thermal desorber for gas chromatography sample introduction with improved compound recovery and enhanced matrix management |
WO2019089688A1 (en) * | 2017-11-03 | 2019-05-09 | Entech Instruments Inc. | High performance sub-ambient temperature multi-capillary column preconcentration system for volatile chemical analysis by gas chromatography |
CN111007188A (en) * | 2019-12-30 | 2020-04-14 | 常州磐宇仪器有限公司 | Water removal and concentration gas circuit system and method for volatile organic compounds in atmosphere |
CN111480073A (en) * | 2017-11-22 | 2020-07-31 | 因泰科设备股份有限公司 | System and method for real-time monitoring of chemical samples |
US11067548B2 (en) | 2016-04-04 | 2021-07-20 | Entech Instruments Inc. | Multi-capillary column pre-concentration system for enhanced sensitivity in gas chromatography (GC) and gas chromatography-mass spectrometry (GCMS) |
US11247204B2 (en) | 2017-10-25 | 2022-02-15 | Entech Instruments Inc. | Sample preconcentration system and method for use with gas chromatography |
US11549921B2 (en) * | 2017-11-22 | 2023-01-10 | Entech Instruments Inc. | System and method for real time monitoring of a chemical sample |
US11946912B2 (en) | 2020-06-30 | 2024-04-02 | Entech Instruments Inc. | System and method of trace-level analysis of chemical compounds |
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US6632268B2 (en) * | 2001-02-08 | 2003-10-14 | Oakland University | Method and apparatus for comprehensive two-dimensional gas chromatography |
KR100712189B1 (en) * | 2004-12-14 | 2007-04-27 | 주식회사 케이엔알 | Apparatus for analyzing SOF of PM emitted from diesel engine |
US7343779B1 (en) | 2005-12-05 | 2008-03-18 | Yu Conrad M | High performance, hand-held gas chromatograph, method and system |
RU2556759C1 (en) * | 2014-06-06 | 2015-07-20 | Федеральное государственное бюджетное образовательное учреждение высшего профессионального образования "Самарский государственный университет" | Method of determining correspondence of chromatographic peaks to same component and apparatus therefor |
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JP7406232B2 (en) | 2019-11-28 | 2023-12-27 | 株式会社ジェイ・サイエンス・ラボ | Temperature programmed desorption analyzer |
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-
2000
- 2000-12-12 JP JP2000377704A patent/JP3460986B2/en not_active Expired - Fee Related
- 2000-12-13 AU AU72189/00A patent/AU770281B2/en not_active Ceased
- 2000-12-13 KR KR10-2000-0075924A patent/KR100479596B1/en not_active IP Right Cessation
- 2000-12-15 US US09/738,543 patent/US6447575B2/en not_active Expired - Lifetime
Cited By (15)
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US9000360B2 (en) | 2010-10-29 | 2015-04-07 | Thermo Fisher Scientific Oy | System layout for an automated system for sample preparation and analysis |
US9236236B2 (en) | 2010-10-29 | 2016-01-12 | Thermo Fisher Scientific Oy | System layout for an automated system for sample preparation and analysis |
US10088460B2 (en) | 2010-10-29 | 2018-10-02 | Thermo Fisher Scientific Oy | Automated system for sample preparation and analysis |
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US20180299415A1 (en) * | 2017-04-14 | 2018-10-18 | Entech Instruments Inc. | Thermal desorber for gas chromatography sample introduction with improved compound recovery and enhanced matrix management |
US11247204B2 (en) | 2017-10-25 | 2022-02-15 | Entech Instruments Inc. | Sample preconcentration system and method for use with gas chromatography |
WO2019089688A1 (en) * | 2017-11-03 | 2019-05-09 | Entech Instruments Inc. | High performance sub-ambient temperature multi-capillary column preconcentration system for volatile chemical analysis by gas chromatography |
US11162925B2 (en) * | 2017-11-03 | 2021-11-02 | Entech Instruments Inc. | High performance sub-ambient temperature multi-capillary column preconcentration system for volatile chemical analysis by gas chromatography |
CN111480073A (en) * | 2017-11-22 | 2020-07-31 | 因泰科设备股份有限公司 | System and method for real-time monitoring of chemical samples |
US11169124B2 (en) * | 2017-11-22 | 2021-11-09 | Entech Instruments Inc. | System and method for real time monitoring of a chemical sample |
US11549921B2 (en) * | 2017-11-22 | 2023-01-10 | Entech Instruments Inc. | System and method for real time monitoring of a chemical sample |
CN111007188A (en) * | 2019-12-30 | 2020-04-14 | 常州磐宇仪器有限公司 | Water removal and concentration gas circuit system and method for volatile organic compounds in atmosphere |
US11946912B2 (en) | 2020-06-30 | 2024-04-02 | Entech Instruments Inc. | System and method of trace-level analysis of chemical compounds |
Also Published As
Publication number | Publication date |
---|---|
AU770281B2 (en) | 2004-02-19 |
KR20010062385A (en) | 2001-07-07 |
KR100479596B1 (en) | 2005-04-06 |
JP2001194354A (en) | 2001-07-19 |
AU7218900A (en) | 2001-06-21 |
JP3460986B2 (en) | 2003-10-27 |
DE19960631C1 (en) | 2001-07-12 |
US6447575B2 (en) | 2002-09-10 |
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