GB2115717A - Supplying liquid sample to capillary gas chromatographic separating columns - Google Patents
Supplying liquid sample to capillary gas chromatographic separating columns Download PDFInfo
- Publication number
- GB2115717A GB2115717A GB08305618A GB8305618A GB2115717A GB 2115717 A GB2115717 A GB 2115717A GB 08305618 A GB08305618 A GB 08305618A GB 8305618 A GB8305618 A GB 8305618A GB 2115717 A GB2115717 A GB 2115717A
- Authority
- GB
- United Kingdom
- Prior art keywords
- needle
- syringe
- separating column
- carrier gas
- liquid sample
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 239000007788 liquid Substances 0.000 title claims abstract description 23
- 239000012159 carrier gas Substances 0.000 claims description 31
- 238000000034 method Methods 0.000 claims description 12
- 239000007789 gas Substances 0.000 claims description 10
- 238000007789 sealing Methods 0.000 claims description 7
- 238000002347 injection Methods 0.000 abstract description 5
- 239000007924 injection Substances 0.000 abstract description 5
- 238000004891 communication Methods 0.000 abstract description 3
- 238000011109 contamination Methods 0.000 abstract description 2
- 229920003023 plastic Polymers 0.000 abstract description 2
- 239000004033 plastic Substances 0.000 abstract description 2
- HPEUJPJOZXNMSJ-UHFFFAOYSA-N Methyl stearate Chemical compound CCCCCCCCCCCCCCCCCC(=O)OC HPEUJPJOZXNMSJ-UHFFFAOYSA-N 0.000 description 6
- 239000002904 solvent Substances 0.000 description 5
- 235000019387 fatty acid methyl ester Nutrition 0.000 description 4
- IIYFAKIEWZDVMP-UHFFFAOYSA-N tridecane Chemical compound CCCCCCCCCCCCC IIYFAKIEWZDVMP-UHFFFAOYSA-N 0.000 description 4
- 238000009835 boiling Methods 0.000 description 3
- 150000001875 compounds Chemical class 0.000 description 3
- RSJKGSCJYJTIGS-UHFFFAOYSA-N undecane Chemical compound CCCCCCCCCCC RSJKGSCJYJTIGS-UHFFFAOYSA-N 0.000 description 3
- FLIACVVOZYBSBS-UHFFFAOYSA-N Methyl palmitate Chemical compound CCCCCCCCCCCCCCCC(=O)OC FLIACVVOZYBSBS-UHFFFAOYSA-N 0.000 description 2
- 238000004587 chromatography analysis Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000004817 gas chromatography Methods 0.000 description 2
- 229930195733 hydrocarbon Natural products 0.000 description 2
- 150000002430 hydrocarbons Chemical class 0.000 description 2
- 239000007791 liquid phase Substances 0.000 description 2
- UQDUPQYQJKYHQI-UHFFFAOYSA-N methyl laurate Chemical compound CCCCCCCCCCCC(=O)OC UQDUPQYQJKYHQI-UHFFFAOYSA-N 0.000 description 2
- ZAZKJZBWRNNLDS-UHFFFAOYSA-N methyl tetradecanoate Chemical compound CCCCCCCCCCCCCC(=O)OC ZAZKJZBWRNNLDS-UHFFFAOYSA-N 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 1
- 125000003178 carboxy group Chemical group [H]OC(*)=O 0.000 description 1
- 230000001427 coherent effect Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 230000002452 interceptive effect Effects 0.000 description 1
- 230000003446 memory effect Effects 0.000 description 1
- -1 polytetrafluorethylene Polymers 0.000 description 1
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 230000003252 repetitive effect Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000009834 vaporization Methods 0.000 description 1
Classifications
-
- 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
- G01N30/16—Injection
- G01N30/18—Injection using a septum or microsyringe
Landscapes
- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Treatment Of Liquids With Adsorbents In General (AREA)
- Sampling And Sample Adjustment (AREA)
Abstract
A liquid sample is injected through a septum into the end 18 of a capillary gas chromatographic separating column 14 by first inserting an auxiliary needle 44, which extends from the end of a cylinder 46 and may be constituted by a conventional plastics syringe; a smaller syringe 48 is fitted into the cylinder 46 with its needle 50 extending through the larger needle 44 and serves for the actual injection of the sample. An O- ring seal 54 prevents any communication between the column 14 and atmosphere thus avoiding sample loss and injection contamination. <IMAGE>
Description
SPECIFICATION
Supplying liquid sample to capillary gas chromatographic separating columns
The present invention relates to the supplying of a liquid sample to a capillary gas chromatographic separating column. Conventionally in gas chromatography a liquid sample is injected into a heated injector and is vaporised therein. The sample vapour thus generated is transported into and through the gas chromatographic separating column by means of a carrier gas flow. The injection is accomplished by means of a syringe having a needle which pierces a septum, usually a self-sealing diaphragm, sealing the interior of the injector.
The term "capillary columns" designates gas chromatographic separating columns having small diameters and relatively long lengths and in which only the interior walls of the column are coated with a gas separating substance. Such capillary columns permit only very small sample volumes. In a conventional injector, however, a relatively large volume of sample vapour is generated. Therefore, a flow divider is required when capillary columns are employed. The flow divider provides a fixed percentage of the sample vapour to the separating column. This flow divider, however, is subject to nonlinearities which often result in erroneous results.
One known solution is to inject the liquid sample directly into the end of the capillary column.
Because of the small inside diameter of the capillary column, a syringe having a very fine needle is required. However, such needles are not rigid enough to pierce a septum. Therefore, valves are provided to permit introduction of the fine needle of the syringe when the valve is in an open position. This, however, suffers from the disadvantage that the entire system is also open during the injection. Hence part of the carrier gas then flows back along the needle, which carrier gas also carries a portion of the sample along with it. To minimise this effect, previous needles for this purpose have been made to a length of 8.5 cm whereby a flow resistance occurs such that, when the needle is inserted into a long needle guide, which is used for a capillary tube, little carrier gas flows therealong.
This, however, creates the following problems. If the needle is inserted into the capillary column and the sample ejected, a portion of the liquid sample travels backwards along the needle by capillary forces. Alternatively, if the needle is retracted, droplets are deposited on all parts in front of the capillary column resulting in memory effects and contamination as well as double peaking.
The use of an auxiliary needle having a comparatively large diameter to pierce the septum of a separating column and the introduction of the needle of a syringe through the auxiliary needle into the end of the capillary column is known from the "Journal of High Resolution Chromatography and
Chromatography Communications" vol. 4, June 1 981. In this previous device, communication between the column and the atmosphere is established through the clearance between the inside diameter of the auxiliary needle and the outside diameter of the fine needle. It has been found that this involves the risk of the carrier gas pressure at the inlet of the separating column breaking down.Consequently, not only is the chromatographic process interrupted, but the interior of the separating column represents an appreciable volume within which the carrier gas is under elevated pressure. When the pressure at the inlet of the separating column breaks down, part of this carrier gas flows back to the inlet of the separating column. Thereby, in turn, part of the sample supplied may be carried out of the inlet of the separating column.
According to the present invention, the septum of a capillary separating column is pierced with an auxiliary needle having a relatively large diameter, the needle of a syringe is inserted into the separating column through the auxiliary needle while sealing the space between the auxiliary needle and the syringe needle, a liquid sample is injected into the end of the separating column by means of the syringe and the syringe needle and the auxiliary needle are withdrawn. In this way it is possible to supply a liquid sample without loss of sample and without the accompanying errors.
An example in accordance with the invention will now be described in greater detail with refernce to the accompanying drawings, in which: Figure 1 is a schematic sectional view of an injector for use with a capillary separating column;
Figure 2 is a sectional view of a needle arrangement supplying a sample; and
Figures 3 and 4 are chromatograms resulting from use of a method according to the present invention.
The apparatus shown in Figure 1 includes an injector 10, preferably made very small. The injector 10 has an interior cavity 12 into which one end 18 of a capillary gas chromatographic separating column 14 freely projects, via a connection 1 6 to the injector 1 0. A socket 20 is formed on the injector 10 co-axial with the end 18 of the separating column 14. A needle guide 22 having a guide passage 24 is arranged in the socket 20, the passage 24 being enlarged and preferably funnel-shaped. The needle guide 22 is sealed in the socket 20 by means of a seal 26 of, for example, polytetrafluorethylene.
The apparatus also includes a septum 28, i.e. a self-sealing diaphragm, disposed across the socket 20. On its outside, the septum 28 is covered by a disc 30 having a central needle guide 32. The disc 30 is held in place by means of a cap nut 34 which is screwed on an outside thread 36 of the socket 20.
The needle guides 32 and 22 are co-operatively co-axial both with each other and with the end 1 8 of the separating column 14.
Thus, the interior cavity 12 of the injector 10 is sealed on the side opposite to the end 1 8 of the separating column by means of the septum 28.
A carrier gas inlet conduit 38 extends into the interior cavity 12 of the injector 1 0. A carrier gas exit conduit 40 extends from the- interior cavity 12 of the injector 10 on the side opposite to the inlet conduit 38, the ends of both conduits being located laterally with respect to the end 1 8 of the separating column 14. The carrier gas can thus flow from the inlet conduit 38 to the exit conduit 40, flowing around and encompassing the end 1 8 of the separating column 14. A needle valve 42 is disposed in the carrier gas exit conduit 40. Further, a pre-heating system (not shown in the drawing) may be provided in the carrier gas inlet conduit 38.
The apparatus shown in Figure 2 is adapted to supply liquid samples to the separating column 14 and includes an auxiliary needle 44 having a relatively large diameter, which needle 44 is arranged on an end face of a hollow cylindrical body 46.
The hollow cylindrical body 46 is open at the end remote from the auxiliary needle 44 and the two together may be a conventional plastics syringe. In the interior of the hollow cylindrical body 46, a syringe 48 having a comparatively fine needle 50 and a barrel 52 is co-operatively arranged for movement in the longitudinal direction with the syringe needle 50 guided within the auxiliary needle 44.
An O-r.ng seal 54 is provided between the barrel of syring 52 and the hollow cylindrical body 46.
In operation, the separating column 14 is sealed from the atmosphere by means of the septum 28.
A liquid sample is introduced into the end 1 8 of the separating column 14 by means of the syringe 48.
To accomplish this, the auxiliary needle 44 is first passed through the septum 28. The needle 50 of the syringe 48 is then inserted through the auxiliary needle 44 and through the guide passage 24 into the end 1 8 of the separating column 14. As a result of the seal 54, the space between the auxiliary needle 44 and the syringe needle 50 is sealed from atmosphere. This sealing prevents carrier gas from flowing out through this space and from carrying liquid sample away. The liquid sample can thus be injected into the end 18 of the capillary column 14 without substantial loss. Subsequently, the needle 50 and finally the auxiliary needle 44 are withdrawn. The septum 28 again provides a tight seal. Thus, the system is never open to the atmosphere.
In the preferred operation, the syringe needle 50 is not inserted more than about 1 mm into the end 1 8 of the separating column 14. This prevents liquid sample from being transported into the annulus between needle 50 and the walls of the separating column 14 along needle 50 by capillary forces and also, when needle 50 is drawn back, prevents sample from being carried back thereby and being deposited on parts of the injector 10 on the inlet side of the separating column 14.
In use, a carrier gas flow is directed through the interior cavity 12 of the injector 10 and around the end 1 8 of the separating column. The carrier gas flow directed into the interior cavity 12 of the injector 10 is larger than the carrier gas flow flowing through the separating column 14. The excess exits through the carrier gas exit conduit 40. The carrier gas flows can be regulated by the needle valve 42. While the injector 10 is maintained at even temperature, the temperature of the end 1 8 of the separating column 14 is preferably regulated by means of the carrier gas flow flowing around this end 18.
The carrier gas flow is kept cool while the sample is being supplied by the syringe 48. This cooling prevents the liquid sample from being pushed out of the syringe 48 and from being vaporised continuously as it is ejected from the needle 50 and thus prevents sample from being smeared over the inside of the separating column 14. Rather, there is a coherent plug of liquid sample formed initially inside the end 1 8 of the separating column 14 cooled by the carrier gas. After the sample has been injected, the carrier gas flow is pre-heated such that rapid vaporisation occurs then and the sample vapour plug is carried into the separating column 1 4.
Figures 3 and 4 are chromatograms recorded employing the technique described herein.
Figure 3 is a chromatogram of fatty acid methylesters. A separating column, a quartz giass capillary 25 mm x 0.3 mm having SE-30 as a liquid phase, was employed. The temperature programme started at an initial temperature of 80"C which was isothermally maintained for about four minutes.
Then there was a programmed increase of temperature by 300C/min up to 2000 C. The second programmed increase of temperature was effected with 80 C/min steps, or increments, up to 3000 C. A flame ionization detector 10 x 1 6 was employed. The solvent was undecane.
Figure 4 is a chromatogram of high boiling hydrocarbons. As separating column, a quartz glass capillary 10 m x 0.3 mm having SE-52 as liquid phase was employed. The temperature programme maintained an initial temperature of 800C for two minutes. A first programmed increase of temperature was effected by 200cumin up to 1 500 C. A second programmed increase of temperature was effected with 80C/min up to 2800 C. As solvent, n-tridecane was employed. The number indicates the
C-numbers of the respective n-paraffins.
In gas chromatography, a critical test is the determination of response factors of fatty acid methylesters, particularly because the higher compounds such as stearic acid methylester are likely to undergo discrimination effects resulting in strong deviations of the theoretical response factor value of nearly 1 000.
In recording the chromatogram of Figure 3, a test mixture of equal amounts of four fatty acid methylesters was analysed as a dilute solution in n-undecane.
As demonstrated by the chromatogram of Figure 3, though the initial temperature of the injector
10 was only 800 C, the stearic acid methylester was eluted without any tailing as a sharp symmetrical peak at a boiling point of about 3600C.
The results of four repetitive determinations are summarised in the following table:
Experimental Theoretical
Compound response factor response factor Lauricacid methylester 1.041 + 1.1% 1.057
Myristic acid methylester 0.991 + 1.4% 1.017
Palmitic acid methylester 1.000 1.000
Stearic acid methylester 1.012 + 0.9% 0.985
The theoretical response factors were calculated from the molecular formula and the molecular weight taking into account the carboxyl configuration which does not contribute to the detector signal.
In addition, the interfering content of impurities of each compound was also included in the calculated theoretical response factor values.
These results with fatty acid methylesters are satisfactory as the deviations from the theoretical values are only 16% and 2.7%.
The chromatogram of Figure 4 shows the analysis of a mixture of hydrocarbons with C-numbers ranging from C18 up to C28, thus corresponding to a boiling range from 2700 to 4300 C.
It is remarkable that the injection temperature was also 800C and that, though n-tridecane (n-C,3) was used as the solvent in excess, the trace of n-Cl2 was well separated from the large solvent peak.
The solvent peak quickly returns to the base line without any tailing.
Claims (1)
1. A method of introducing a liquid sample to a capillary gas chromatographic separating column sealed by means of a septum, in which method the septum is pierced with an auxiliary needle having a relatively large diameter, the needle of a syringe is inserted into the separating column through the auxiliary needle while sealing the space between the auxiliary needle and the syringe needle, a liquid sample is injected into the end of the separating column by means of the syringe and the syringe needle and the auxiliary needle are withdrawn.
2. A method accordingto claim 1 in which the syringe needle is inserted not more than about 1 mm into the end of the separating column.
3. A method according to claim 1 or claim 2 wherein the auxiliary needle extends from an end face of a hollow cylindrical body, the barrel of the syringe is inserted into the hollow cylindrical body and the annulus between the hollow cylindrical body and the barrel of the syringe is sealed.
4. A method according to any one of the preceding claims in which a carrier gas flow is introduced into the interior cavity of an injector sealed by the septum and around the end of the separating column which projects freely into the interior cavity, the carrier gas flow is cooled while the sample is being supplied by the syringe and the carrier gas flow is pre-heated after the liquid sample has been supplied.
5. A method according to claim 4 in which the carrier gas flow into the interior cavity of the injector is larger than the carrier gas flow flowing through the separating column.
6. A device for introducing a liquid sample into a capillary gas chromatographic column and comprising an injector, having an interior cavity into which the end of the column freely projects, the interior cavity being sealed by a septum on the side opposite the end face of the column, a carrier gas inlet conduit ending in the interior cavity and a carrier gas exit conduit leading from the interior cavity.
7. A device according to claim 6 wherein the carrier gas inlet and exit conduits extend from opposite sides of the cavity at points spaced laterally with respect to the end of the separating column whereby the carrier gas flow from the inlet conduit to the exit conduit flows around the end of the separating column.
8. A device for carrying out a method according to claim 1 and comprising an auxiliary needle extending from the closed end face of a hollow cylindrical body, a syringe having a needle which is sufficiently fine to pass through the interior of the auxiliary needle, the syringe being arranged for longitudinal movement in the interior of the hollow cylindrical body, with the syringe needle guided by the auxiliary needle and a seal between the barrel of the syringe and the hollow cylindrical body.
9. A device according to claim 8, wherein the seal is an O-ring.
10. A device for introducing a liquid sample into a capillary gas chromatographic column substantially as described and as illustrated with reference to either Figure 1 or Figure 2 of the accompanying drawings.
New claims or amendments to claims filed on 5/5/83.
Superseded claims 1.
New or amended claims:
1. A method of introducing a liquid sample to a capillary gas chromatographic separating column sealed by means of a septum, in which method the septum is pierced with an auxiliary needle having a relatively large diameter, the needle of a syringe is inserted into the separating column through the auxiliary needle while sealing the space between the auxiliary needle and the syringe needle from atmosphere, a liquid sample is injected into the end of the separating column by means of the syringe and the syringe needle and the auxiliary needle are withdrawn.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19823207386 DE3207386A1 (en) | 1982-03-02 | 1982-03-02 | METHOD AND DEVICE FOR APPLYING A LIQUID SAMPLE TO A GAS CHROMATOGRAPHIC SEPARATION COLUMN DESIGNED AS A CAPILLARY COLUMN |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB8305618D0 GB8305618D0 (en) | 1983-03-30 |
| GB2115717A true GB2115717A (en) | 1983-09-14 |
Family
ID=6157055
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB08305618A Withdrawn GB2115717A (en) | 1982-03-02 | 1983-03-01 | Supplying liquid sample to capillary gas chromatographic separating columns |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS58193457A (en) |
| DE (1) | DE3207386A1 (en) |
| GB (1) | GB2115717A (en) |
| IT (1) | IT1161626B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5336412A (en) * | 1989-01-03 | 1994-08-09 | Stratagene | Push column chromatography method |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0491351U (en) * | 1990-12-21 | 1992-08-10 |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3730002A (en) * | 1969-06-24 | 1973-05-01 | Varian Associates | Sample introduction system for a fluid chromatograph |
-
1982
- 1982-03-02 DE DE19823207386 patent/DE3207386A1/en not_active Withdrawn
-
1983
- 1983-02-28 IT IT19830/83A patent/IT1161626B/en active
- 1983-03-01 GB GB08305618A patent/GB2115717A/en not_active Withdrawn
- 1983-03-01 JP JP58031883A patent/JPS58193457A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5336412A (en) * | 1989-01-03 | 1994-08-09 | Stratagene | Push column chromatography method |
| US5378359A (en) * | 1989-01-03 | 1995-01-03 | Strategene | Push column and chromatography method |
| US5378360A (en) * | 1989-01-03 | 1995-01-03 | Stratagene | Push column and chromatography apparatus |
| US5413708A (en) * | 1989-01-03 | 1995-05-09 | Stratagene | Push column chromatography apparatus |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS58193457A (en) | 1983-11-11 |
| DE3207386A1 (en) | 1983-09-15 |
| GB8305618D0 (en) | 1983-03-30 |
| IT1161626B (en) | 1987-03-18 |
| IT8319830A0 (en) | 1983-02-28 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |