JPH0943219A - Gas chromatograph - Google Patents

Abstract

PROBLEM TO BE SOLVED: To raise decomposition capability in a column. SOLUTION: A detector 5 to detect the eluting component of sample separated in a column 1 is provided at the outlet of the column 1 and the downstream of the detector 5 is opened to the atmosphere by way of a channel resistance 7. The detector 5 is supplied with carrier gas pressure-controlled by an pressure control valve 9 by way of a carrier gas bomb and a bypass channel 8 so as to raise the pressure in the detector 5 and the column 1 higher than the atmospheric pressure. Because of the high pressure in the column 1, the decomposition capability is raised.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a gas chromatograph for separating and analyzing a sample containing various compounds.

[0002]

2. Description of the Related Art A gas chromatogram is provided with a sample vaporization chamber or a sample introduction part on the column inlet side along a carrier gas flow path, a detector on the column outlet side, and the downstream of the detector is generally in the atmosphere. It is open or decompressed. When performing analysis with a gas chromatograph, sufficient sensitivity cannot be obtained when the concentration of the analyte component in the sample is extremely low. In order to increase the detection sensitivity, it is necessary to take either measure to increase the resolution on the column to make the peak of the chromatogram sharper or to increase the sensitivity of the detector to increase the sensitivity. .

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to enhance sensitivity by increasing the resolution in the column and reduce the minimum detectable sample amount even when the conventional column and detector are used. To do.

[0004]

In the present invention, a pressurizing mechanism is provided in the flow path downstream of the detector. The resolution in gas chromatography is Van Deemte
It is represented by the equation (1) of r.

[0005]

[Equation 1]

Here, H is the theoretical plate height, and the smaller the value of H, the better the resolution, the sharper the peak of the obtained chromatogram, and the higher the sensitivity. Rt is the retention time, which is the time during which the sample is transported from the column inlet to the column outlet, and is usually several minutes to several hours. A is a coefficient relating to multi-channel diffusion, B is a coefficient relating to gas diffusion, C is a coefficient relating to resistance to gas movement in a column liquid phase, x is a distance from a column inlet, L is a column length, and P is a column inlet. Is the pressure at the position of distance x.

As is clear from the above equation (1), the higher the pressure in the column, the better the resolution. Since the retention time is determined by the pressure difference between the column inlet pressure Pin and the column outlet pressure Pout, in order to obtain the same retention time as when the column outlet is open to the atmosphere, it is necessary to increase the column outlet pressure. The column inlet pressure applied to the sample vaporization chamber or the sample introduction part may be increased.

Even when the retention time is set not to change by increasing the pressure in the column, the resolution becomes high, the peak of the chromatogram becomes sharp and the sensitivity becomes high, and the minimum sample that can be detected. The amount becomes smaller.

FID as a detector for a gas chromatograph
(Flame ionization detector) and FDT (flame therm
In a detector that causes a chemical reaction such as combustion in a sample like the oionic detector) and detects the resulting current or voltage, the chemical reaction is generally accelerated as the pressure increases, so The higher pressure also increases the sensitivity of the detector. In this respect also, the minimum sample amount that can be detected becomes low. TCD (thermal conductivity d
It can be expected to improve the sensitivity with pressure rise even in other detectors that do not involve direct chemical reaction, such as the etector).

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first embodiment. Carrier gas is supplied to the column 1 from the carrier gas cylinder 3 via the pressure control valve 4. A sample vaporization chamber 2 is provided in the carrier gas flow path between the pressure control valve 4 and the column 1, and the sample introduced into the sample vaporization chamber 2 is vaporized and introduced into the column 1 by the carrier gas. A detector 5 for detecting a sample component separated and eluted in the column 1 is provided at the outlet of the column 1, and the downstream side of the detector 5 is open to the atmosphere via a flow path resistance 7. The detector 5 is an FID or FTD.
A carrier gas whose pressure is adjusted by a pressure control valve 9 is supplied from a carrier gas cylinder to the detector 5 through a bypass flow passage 8 so that the pressure in the detector 5 and the column 1 can be made higher than the atmospheric pressure. There is.

FIG. 2 shows a second embodiment. The carrier gas is supplied from the carrier gas cylinder 3 to the column 1 via the pressure control valve 4 and the sample vaporization chamber 2, and the detector 5 is provided at the outlet of the column 1 as in the embodiment of FIG. In order to increase the pressure in the detector 5 and the column 1, a back pressure control valve 10 is provided in the flow path downstream of the detector 5, and the back pressure control valve 10 is adjusted to adjust the detector 5 and the column 1. The pressure of can be set higher than the atmospheric pressure.

In the embodiments of FIGS. 1 and 2, in order to make the retention time data of the standard substance measured by opening the column outlet side to atmospheric pressure, the pressure at the column outlet side is increased. Accordingly, the column inlet pressure may be set by the pressure control valve 4 to adjust the differential pressure between the column inlet pressure and the outlet pressure.

[0013]

According to the present invention, the pressure in the column is set higher than that in the conventional case where the column outlet is opened. Therefore, even if the retention time is the same, the detection sensitivity is increased and the minimum detectable value is obtained. It becomes possible to perform an analysis with a small sample amount. The increased pressure in the detector also improves the sensitivity of the detector that involves a chemical reaction, and in this respect as well, it becomes possible to perform an analysis with a small minimum sample amount. On the contrary, when the same minimum detection amount is required as compared with the conventional case, by increasing the differential pressure between the column inlet pressure and the outlet pressure as compared with the conventional case, it becomes possible to perform analysis with a short retention time. .

[Brief description of drawings]

FIG. 1 is a flow chart showing a first embodiment.

FIG. 2 is a flow chart showing a second embodiment.

[Explanation of symbols]

 1 column 2 sample vaporization chamber 3 carrier gas cylinder 4, 9 pressure control valve 5 detector 7 flow path resistance 8 bypass flow path 10 back pressure control valve

Claims (1)

[Claims] 1. A sample vaporization chamber or a sample introduction part is provided on the column inlet side along a carrier gas flow path, a detector is provided on the column outlet side, and a pressurizing mechanism is provided on the column outlet side. A gas chromatograph characterized by