JPH09159660A - Gas chromatograph - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the accuracy of analysis by a constitution wherein a sample passed through a branch part is cold trapped again and overlap is eliminated by sharpening the peak of each component thereby enhancing the separation. SOLUTION: A sample S subjected to first cold trap 20 in a trap tube 3 is introduced again to the duct part 21a in a jacket from a T pipe through a duct 12 and liquid nitrogen LN is fed to the jacket 2 in order to trap and focus the sample S again. Subsequently, a current is fed instantaneously to the duct part 21a through voltage applying terminals 22a, 22b and the sample S is heated at a stretch. The focused sample S is evaporated under that state and introduced to a separation column 12. Since the sample S passed through a T pipe 9 is trapped and focused again, bandwidth of the sample S is reduced and the peak of each component is sharpened. Consequently, overlap of peak is eliminated and the separation is enhanced thus enhancing the accuracy of analysis.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a gas chromatograph by a cold trap method.

[0002]

2. Description of the Related Art FIG. 2 shows a general configuration of a gas chromatograph by a cold trap method. In this figure, 1 is a cold trap, and a jacket 2 to which liquid nitrogen LN as a refrigerant is supplied is The trap tube 3 made of metal in which the sample S and the carrier gas CG flow is inserted. Reference numerals 4a and 4b denote voltage application terminals for applying a voltage for causing a current to flow through the trap tube 3 to generate heat, and a power source (not shown) is connected thereto.

Reference numeral 5 denotes a sample injecting portion provided on one end side of the cold trap 1. A syringe 7 for injecting the sample S is connected to one port of the three-way solenoid valve 6 and the other side of the three-way solenoid valve 6 is connected. A carrier gas cylinder 8 containing a carrier gas CG such as He is connected to the port.

Reference numeral 9 denotes a branch portion provided on the other end side of the cold trap 1, which is made of, for example, a T-shaped pipe made of resin or metal, and a pipe line 10 connected to one of the connecting portions 9a is
Separation column 12 and analysis unit 13 housed in the oven 11
And are provided in that order. In addition, a solenoid valve 15 and a suction pump 16 are provided in this order in the conduit 14 connected to the other connecting portion 9b of the branch portion 9. In addition, pipeline 1
0 and 14 are made of a material having excellent corrosion resistance such as stainless steel.

In the gas chromatograph thus constructed, the solenoid valve 15 is opened, the suction pump 16 is operated, and the sample S is supplied to the trap tube 3. The sample S is once condensed by flowing, and then the trap tube 3
Is heated very rapidly to vaporize the condensed sample S, and then the solenoid valve 15 is closed to supply the carrier gas CG to the trap tube so that the vaporized sample S is sent to the column 12 direction. ing.

[0006]

By the way, the T-shaped tube 9
However, in the conventional cold trap 1, since the trapped and focused sample S passes through the T-tube 9 before entering the separation column 12, the dead volume is unavoidable due to its structure. Due to the influence of the dead volume, the band width of the sample S is spatially widened, which adversely affects the separation of each component in the separation column 12 following the cold trap 1 and, as a result, is obtained in the analysis unit 13. There were points to be improved in separability of peaks and analytical sensitivity in the chromatogram.

The present invention has been made in view of the above matters, and an object thereof is to be able to satisfactorily separate peaks in a gas chromatograph by the cold trap method and to analyze with high accuracy. It is to be.

[0008]

In order to achieve the above object, according to the present invention, when a sample that has been cold trapped and condensed is vaporized by heating and is fed to a separation column through a branching portion, The pipe connected to the branch is guided to the cold trap portion so that the sample passing through the branch is trapped again.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, an introduced sample is condensed in a trap tube in a cold trap,
In a cold trap configured to vaporize the condensed sample by heating and feed it toward the separation column through the branch part, a pipe connected to the branch part is guided to a portion for cold trapping, The sample that has passed through the branch portion is configured to be trapped again.

In the gas chromatograph having the above structure, the sample is trapped in two stages. The sample is condensed in the first trap, and the sample is subjected to predetermined focusing. Then, the heated and vaporized sample is affected by the T-tube, but is re-trapped and re-focused by the passage connected to the T-tube passing through the cold trap portion. As a result, the band width of the sample is reduced, the peaks of the components are sharpened, the peaks of the components are not overlapped, the separability is improved, and the accuracy is improved.

When the pipe connected to the branching portion is inserted through the cold trap which first performs the trap, only one cold trap is required and the structure is simplified.

[0012]

Embodiments will be described with reference to the drawings. FIG. 1 shows an embodiment of the present invention. In this figure, the reference numerals in FIG. 2 indicate the same things.

In FIG. 1, reference numeral 20 denotes a cold trap, and inside the jacket 2, a trap tube 3 having one end connected to the sample injection part 5 and the other end connected to a T-shaped tube 9 is provided.
Is provided. The configuration so far is no different from that of the gas chromatograph shown in FIG. In the gas chromatograph in this embodiment, the conduit connected to the T-shaped tube 9 is led to a portion for cold trapping, and T
The sample passing through the character tube 9 is configured to be trapped again.

That is, in FIG. 1, reference numeral 21 denotes a pipe line connected to the T-shaped pipe 9, which is made of a material having excellent corrosion resistance such as stainless steel, and has a cold trap 20.
It is inserted through the jacket 2 of the separation column 1 and the downstream side is the separation column 1.
2 are connected. 22a and 22b are jackets 2
A power source (not shown) is connected to a voltage applying terminal for applying a voltage for causing a current to flow in the inner pipe portion 21a to generate heat.

In the gas chromatograph having the above-mentioned structure, by opening the solenoid valve 15 and operating the suction pump 16 to supply the sample S to the trap tube 3, the liquid nitrogen LN is caused to flow through the jacket 2. The sample S is once condensed and the first trap is performed.

Next, an electric current is instantaneously passed through the trap tube 3 to heat the trap tube 3, vaporize the condensed sample S, and supply the carrier gas CG to the trap tube 3, whereby the sample S is trapped. Drive out of 3. At this time, the solenoid valve 15 is closed.

The sample S expelled from the trap tube 3 is guided again into the cold trap 20 via the T-shaped tube 9 and the pipe 21, and in that state, the sample S is made by flowing liquid nitrogen LN into the jacket 2. It is trapped again and focused.

Finally, the trapped sample S is heated at a stroke by instantly passing an electric current through the conduit portion 21a in the jacket 2, and the focused sample S is vaporized in that state, and the sample S is directed toward the separation column 12. Be led to.

As described above, in the gas chromatograph of the present invention, the sample is trapped in two steps, the sample S is condensed in the first trap, the sample is focused, and the sample after passing through the T-shaped tube 9 is sampled. By retrapping and refocusing S, the band width of sample S is prevented from widening. Therefore, the peaks of the components are sharpened, the peaks of the components are not overlapped, the separability is improved, and the accuracy is improved.

Further, in the above-mentioned embodiment, since the cold trap 20 is carried out twice, the structure of the cold trap portion is simple.

The present invention is not limited to the above-described embodiment. For example, a dedicated small cold trap different from the cold trap 20 is provided, and the pipe line 21 connected to the T-shaped pipe 9 is provided in this cold pipe. Alternatively, the trap may be guided to the separation column 12 after being guided to the trap and inserted therethrough.

The trap tube 3 may be a double tube in which a tube made of fused silica is covered with a metal tube.

[0023]

The present invention is embodied in the above-described embodiment and has the following effects.

Since the adverse effect on the sample at the branch portion can be eliminated and a sample having a narrow bandwidth can be supplied to the separation column, the peaks of the respective components are sharpened and the overlapping of the respective components is eliminated. The degree of separation is improved, and the component analysis can be performed accurately. In addition, the analysis can be performed efficiently.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an example of the configuration of a gas chromatograph of the present invention.

FIG. 2 is a diagram schematically showing a configuration of a conventional gas chromatograph.

[Explanation of symbols]

3 ... Trap tube, 9 ... Branch section, 12 ... Separation column, 20
… Cold trap, 21… Pipe, S… Sample.

Claims (2)

[Claims] 1. A cold trap configured to condense the introduced sample in a trap tube in a cold trap, vaporize the condensed sample by heating, and feed the vaporized sample toward a separation column through a branch section. A gas chromatograph characterized in that a pipe connected to the branching portion is introduced to a portion for cold trapping, and a sample passing through the branching portion is trapped again. 2. The gas chromatograph according to claim 1, wherein the pipe line connected to the branch portion is inserted through a cold trap that first performs a trap.