JPS628527Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas chromatograph, particularly a gas chromatograph having a pre-cut device.

A pre-cut device for a gas chromatograph, for example, as disclosed in Japanese Unexamined Patent Publication No. 49-27290, allows a large amount of diluted sample to pass through a pre-column to essentially separate it into an analyte sample and a non-analyte sample.
Release non-analytical samples that interfere with analysis from the device,
This is a device that selectively introduces only the sample to be analyzed into the analysis chamber, and is installed in the discharge flow path to separate the injected sample into the sample to be analyzed and the non-analyte sample and release the non-analyte sample to the outside of the device. The device is configured so that non-analyte samples are discharged from the device by operating a switching valve located inside the device, and only samples to be analyzed are introduced into the analysis column of the gas chromatograph.

However, in a gas chromatograph equipped with such a pre-cut device, when the temperature of the pre-column and analytical column or the junction is raised, components retained or adsorbed at the junction of the pre-column and analytical column and in the discharge channel become ghost peaks. There was a drawback that it appeared on the analysis results.

The purpose of the present invention is to provide a gas chromatograph equipped with a pre-cut device capable of reducing ghost peaks, in which a pre-column is connected to an analytical column, and a non-analytical sample is placed outside the device at the junction between the analytical column and the pre-column. A gas chromatograph having a flow path for discharging the non-analyzed sample to the outside of the device, wherein a purge gas inlet is provided between the junction and the analytical column, and the flow path for discharging the non-analyzed sample to the outside of the device has two branch paths; One of them is opened to the atmosphere through a needle valve and a resistance pipe, and the other is opened to the atmosphere through a resistance pipe and a stop valve, and furthermore, heating means is provided in the flow path from the joint to the branch path. It is characterized by the fact that it is provided.

That is, the present invention prevents gases stagnant or adsorbed in the joints and discharge channels from flowing into the analytical column during the operation of the apparatus, thereby reducing the occurrence of ghost peaks in the gas chromatogram.

Examples will be described below.

FIG. 1 shows one embodiment, which consists of an analytical column part 1, a pre-column part 2, and a non-analyte sample discharge channel part 4. The analytical column part 1 has a sample injection fitting 11
It consists of an analytical column 14 fixed with a nut 13 via an O-ring 12, and a constant temperature bath 16 having an injection fitting heater 15 disposed around an analysis sample injection fitting 11. 141 and a filler 142 are inserted, and the analysis sample injection fitting 11 is provided with a purge gas inlet 111 for purging the dead volume at the junction between the pre-column 21 and the analysis column 14. Pre-column section 2 attached to the top of analytical column section 1
is a pre-column 2 into which a packing material 211 is held at both ends by quartz wool 212 and 213.
1 as a main body, and the pre-column 21 has a joint 22 between its lower end and the upper end of the analytical column section 1.
is connected to the analysis column 14 using nuts 24 and 25 via the O-ring 20 and packing 23, and a carrier gas introduction fitting 26 having a carrier gas inlet 261 at the upper end is connected to the O-ring 27.
The injection rubber septum 2 is attached to the upper end of the carrier gas introduction fitting 26 via a nut 28.
9 is attached by a nut 30. A pre-column heater 31 is disposed around the outer periphery of a portion of the pre-column 21 that is filled with the filler 211 . The non-analysis sample discharge channel section 4 is a joint 2.
A branch pipe 41 attached to 2 is connected to a solvent adsorption tube 42 filled with activated carbon or the like and a stop valve 43 to form a non-analysis gas outlet 44, and the branch pipe 41 has a needle valve 45,
The branch pipe 41 has a bypass flow path having a resistance pipe 46 and a leak gas outlet 47, and furthermore, the branch pipe 41 is provided with a bent portion 411 located in the middle so as to be in contact with the injection fitting heater 15. The constant temperature oven heater 161, the power source 311 of the pre-column heater 31, and the stop valve 43 are controlled by the time control section 48.

In a chromatograph having such a configuration, the carrier gas introduced from the carrier gas inlet 261 passes through the pre-column 21, and then a portion passes through the analytical column 14 to reach the detector (not shown) of the gas chromatograph. The other part passes through the branch pipe 41 and is exhausted from the non-analysis gas outlet 44 or the leak gas outlet 47. Furthermore, the purge gas introduced from the purge gas inlet 111 passes between the analytical column 14 and the sample injection fitting 11, purges the dead volume at the joint between the pre-column 21 and the analytical column 14, and, like the carrier gas, passes through the analytical column 14.
and is discharged through branch column 41. In this way, the injection rubber septum 2 is inserted into the gas chromatograph where the carrier gas and purge gas are flowing.
When a large amount of diluted sample is injected with a syringe through 9, it is sent to a pre-column 21 by a carrier gas, and is separated into an analyte sample and a non-analyte sample by the pre-column 21. The sample to be analyzed separated from the non-analyte sample by the pre-column 21 is sent to the analysis column 14, where each component is separated and measured and detected by a detector (not shown). On the other hand, non-analytical samples pass through a branch pipe 41 to a stop valve 4.
At this time, the dead volume at the junction between the pre-column 21 and the analytical column 14 and the gas in the branch pipe 41 are discharged to the outside of the apparatus from the needle valve 45 and the resistance pipe 46 at a constant minute flow rate. The leak gas is flowing out from the leak gas outlet 47.

In addition, when the non-analyte sample is a low-boiling point solvent, etc., the pre-column 21 is at room temperature, so the stop valve 43 is kept open, and after most of the solvent has flowed out from the non-analyte gas outlet 44, the pre-column 21 is at room temperature. The sample to be analyzed with a high boiling point is gasified by raising the temperature of the pre-column heater 31, and if the stop valve 43 is closed at this time, most of the gas to be analyzed is sent to the analysis column 14. At this time, when the branch pipe 41 is at room temperature, the temperature of the branch pipe 41 rises due to the rise in temperature of the pre-column 21, and as a result, the pre-column 21, which is constantly discharged in a small amount through the leak gas outlet 47, and the analysis The dead volume at the junction with the column 14 and the solvent in the branch pipe 41 are
As the temperature increases, it expands again and flows back into the analytical column 14, producing a ghost peak. Therefore, in this embodiment, the branch pipe 41 is provided with a bent portion 411 arranged so as to be in contact with the injection fitting heater 15, and the branch pipe 41 is maintained at a constant temperature by the injection fitting heater 15. In this way, when the branch pipe 41 is maintained at a constant temperature, the temperature of the branch pipe 41 does not rise due to the rise in temperature of the pre-column 21, so no backflow of solvent from the branch pipe 41 occurs and ghost peaks occur. can be prevented from occurring.

Figures 2 a and b show the disappearance of ghost peaks, with the horizontal axis plotting time and the vertical axis plotting the chromatographic output. This figure shows the results obtained using the above apparatus, in which A shows the solvent peak, B shows the peak to be measured, and C shows the ghost peak due to re-mixing of the solvent.

In addition, when a large amount of solvent is discharged, the solvent is adsorbed by the adsorption tube 42 in order to deteriorate the rubber packing of the stop valve 43, etc.

In addition, in this embodiment, the pre-column 21
Since the pre-column is not installed in the analytical column constant temperature bath 16 and is separated, unlike the conventional case where the pre-column was installed in the analytical column constant temperature bath, the temperature of the pre-column is raised at the same time as the analytical column, and the next time The entire column constant temperature bath had to be cooled during the analysis, which did not cause the problem of prolonging the analysis period, and it was impossible to perform the analysis by keeping the analytical column at a constant temperature. On the other hand, in the device of this example, the pre-column is installed outside the analytical column constant temperature bath, so it is possible to perform constant temperature analysis in which the analytical column constant temperature bath is kept at a constant temperature, and the pre-column can also be cooled outside the analytical column. Cooling is easy because it is outside the constant temperature bath.

Note that since the pre-column 21 is a straight tube, it has the advantage that a sample injection fitting for a normal gas chromatograph can be used as is.

Furthermore, if the time control unit 48 controls the power supply 311 of the pre-column heater 31, the stop valve 43, for example, a solenoid valve, the temperature rise by the constant temperature oven heater 161, etc., it is possible to automatically perform analysis after sample injection. .

In the above embodiment, a pre-column heater was provided separately, but depending on the purpose of use, the entire pre-column may be placed in an air constant temperature bath.The main effect in this case is the same as in the embodiment, but the pre-column heater This has the advantage of improving temperature distribution.

FIG. 3 shows another embodiment, which is a gas chromatograph using a splitless injection device using a capillary column, in which the same parts as in FIG. 1 are given the same reference numerals. In the figure, 51 is a capillary column, 52 is a hydrogen flame ionization detector, and the operation for exhausting the solvent in this gas chromatograph is the same as in the embodiment shown in FIG. A column constant temperature bath (not shown) is maintained at room temperature, sample components are collected at the tip of the capillary column 51, and then,
A sharp peak is obtained by raising the temperature of the column constant temperature bath.

As described above, the gas chromatograph described in the example is capable of constantly purging a small amount of gas, and furthermore, the branch pipe is kept at a constant temperature. This prevents the solvent from re-expanding due to temperature rise and contaminating the analytical column, making it possible to remove ghost peaks and obtain a clean chromatograph.

As described above, the gas chromatograph of the present invention is
This makes it possible to reduce ghost peaks in gas chromatographs, and has great industrial effects.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional explanatory diagram of a main part of one embodiment of the gas chromatograph of the present invention, Fig. 2 a and b are diagrams showing the same effect in comparison with a conventional example, and Fig. 3 is an explanation of another embodiment. It is a diagram. 1...Analysis column section, 11...Sample injection fitting,
14... Analysis column, 15... Injection fitting heater,
2... Pre-column part, 21... Pre-column, 31
... Pre-column heater, 4 ... Non-analysis sample discharge flow path section, 41 ... Branch pipe, 411 ... (branch pipe) bent part, 42 ... Solvent adsorption tube, 43 ...
Stop valve, 44...Non-analysis gas outlet, 45
...Needle valve, 46...Resistance tube, 47...
leak gas outlet.

Claims (1)

[Claims for Utility Model Registration] 1. A gas chromatograph in which a pre-column is connected to an analytical column, and a flow path for discharging a non-analytical sample to the outside of the device is provided at a junction between the analytical column and the pre-column, wherein the junction and the A purge gas inlet is provided between the analytical column and the flow path for discharging the non-analytical sample to the outside of the apparatus, and the flow path has two branch paths, one of which is opened to the atmosphere through a needle valve and a resistance pipe, and the other is open to the atmosphere through a resistance pipe and a stop valve,
Furthermore, the gas chromatograph is characterized in that a heating means is provided in the flow path between the joint portion and the branch path. 2. The gas chromatograph according to claim 1, wherein the heating means is also used as a heating means disposed around a sample injection fitting that fixes the analytical column. 3. The gas chromatograph according to claim 1, wherein the heating means is a heating means independent of a heating means disposed around a sample injection fitting that fixes the analytical column.