JPH0213967Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of a thermal conductivity type detector for a gas chromatograph.

What is a gas chromatograph? As shown in Figure 1, a carrier gas such as He or Ar is fed into the carrier gas inlet 1, and the flow rate of the carrier gas is controlled by adjusting the pressure regulating valve 2, flow rate regulator 3, pressure gauge 4, and flow meter 5. The gas is maintained at a constant rate (20 to 60 ml/mm), flows through the sample introduction section 6 into the separation tube 8, passes through the detector 10, and is discharged to the outside from the carrier gas outlet 12.

At this time, the sample introduction section 6, separation tube 8, detector 10
etc., are controlled to the required temperature by a separation tube tank 7 and a detector tank 9. That is, the separation tube tank 7 and the detector tank 9 function as a constant temperature bath with a set temperature, and are controlled to this set temperature.

When a sample is introduced from the sample introduction part 6, the gas remains as it is, the liquid or solid is heated and vaporized, and then sent into the separation tube 8 by the carrier gas, and each component in the sample is separated by the filling in the separation tube 8. The signals are separated and sequentially passed through the detector 10.

Detector 10 is shown in detail in FIGS. 2 and 3.

Detector 10 changes the thermal conductivity around filament 10A as the sample and carrier gas mixture passes from gas inlet 10B to gas outlet 10C.

The detector 10 has a measurement cell 10f and a comparison cell 1.
0g, and those based on various principles are used, but in any case, a series of electric signals corresponding to each component are converted into an electric signal having a certain relationship with the amount of the component, amplified and separated by the amplifier 10e. A chromatogram 11 consisting of peaks is obtained.

Since the area and height of the peak on this chromatogram 11 have a certain relationship with the component amount of the sample, quantitative analysis can be performed based on this.

Next, the detector 10 (thermal conductivity type) will be explained.
A stable current is passed through the filament at 10A. The carrier gas from the separation pipe 8 is connected to the gas inlet 1.
When heat flows into the filament 10 from 0B and is released from the gas outlet 10C, heat is transferred to the filament 10 at a constant rate.
A is taken away from A, but eventually an equilibrium state at a constant temperature is reached.

When another gas component, ie, a sample, flows in here, its thermal conductivity changes, so the temperature of the filament 10A changes, and the electrical resistance changes accordingly. This is detected by a Wheatstone bridge circuit via a lead wire 10d.

When analysis is performed using a gas chromatograph equipped with a detector configured in this manner, fine dust such as powder from the filler in the separation tube and glass wool may flow into the detector along with the carrier gas, causing damage to the filament. This adheres and obstructs heat conduction to the filament or causes vibrations to the filament, resulting in noise, which reduces analytical sensitivity and accuracy and often interferes with stable quantitative analysis.

Further, it is not easy to remove the attached dust, and the gas chromatograph in operation must be temporarily stopped, which results in a waste of time.

The thermal conductivity detector for gas chromatographs of the present invention has a protective tube with a small hole at the bottom that surrounds the filament disposed in the internal space, and a protective tube that communicates with the lower part of the outer circumferential space of the protective tube to prevent dust, etc. an eject mechanism for discharging a fluid containing the filament, a means for heating the filament to a predetermined temperature, an amplifier connected to the filament by a lead wire, and a means for displaying an electrical signal amplified by the amplifier. Since the gas is introduced from the upper part of the space and the gas is discharged from the upper part of the protective cylinder, it is not possible to completely prevent dust from entering. It is possible to perform stable quantitative analysis.

That is, in the present invention, impurities and the like that are entrained in the carrier gas and flow in can be discharged into the atmosphere through the ejector mechanism without coming into contact with the filament. Therefore, it is a drawback of conventional detectors. It is possible to eliminate noise generation during analysis and decrease in analysis sensitivity due to fine dust such as filler powder and glass wool or coating agent adhering to the filament. In addition, in the dry baking operation of the separation tube,
Conventionally, it was necessary to separate the separation tube from the detector to prevent impurities from entering the detector, but with this invention, the impurities can be released into the atmosphere through the ejector mechanism without coming into contact with the filament. This can be done with the detector connected.

The present invention will now be described with reference to an embodiment of the detector shown in FIG.

In the figure, 10 is a detector, which has an internal space S and is provided with a filament 10A.
A gas inlet 10B is communicated above it. 1
0E is a protective cylinder surrounding the filament 10A, with a small hole 10I opening at the bottom and a gas outlet 10C having a valve 10D connected to the top. The size of the small hole 10I is 2 to 3 mm in inner diameter.
is optimal.

A plurality of eject pipes 10G are opened at the lower part of the space S on the outer periphery of the protection tube 10E via valves 10H, and the eject pipes 10G are connected to the ejector 1
0F, and the fluid (including dust, etc.) in the space S is exhausted.

The detector 10 constructed in this manner is installed as shown in Fig. 1, and the sample is analyzed using a gas chromatograph. Close the valve 10H and open the valve 10H to prevent the impurities, etc. that flow in from the gas inlet 10B, accompanied by the carrier gas, from coming into contact with the filament 10A.
G, released into the atmosphere via ejector 10F.

2. During the analysis operation, open the gas outlet valve 10C and close the valve 10H.

Gas inlet 1 with carrier gas during analysis
Impurities such as the coating agent flowing in from 0B are contained in the protective tube 10E and the pores 10I at its lower part.
The trapped debris falls to the bottom of the detector 10 and accumulates.

3. When cleaning the inside of the detector 10, flow the carrier gas from the gas inlet 10B, close the valve 10C, open the valve 10H, and flow the fluid (gas or water) into the ejector 10F at high speed.
The pressure inside 0G is reduced and the dust accumulated at the bottom of the detector 10 is suctioned and removed.

By doing so, the detector of this embodiment avoids the problem of conventional detectors, where fine dust such as packing powder and glass wool or coating agents adhere to the filament, causing noise during analysis. , it is possible to eliminate a decrease in analytical sensitivity.

Furthermore, in the dry firing operation of the separation tube, conventionally it is necessary to separate the separation tube from the detector, but by using the one of this embodiment, the operation can be performed while the separation tube and the detector are connected.

Furthermore, since it has a gas outlet valve, when stopped,
By keeping this valve closed, it is possible to prevent air from entering the tube, and the filling in the separation tube does not absorb moisture, thereby preventing the filling from deteriorating.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram of a gas chromatograph, Figure 2 is a circuit diagram of a thermal conductivity detector, Figure 3 is a sectional view of a conventional thermal conductivity detector, and Figure 4 is an embodiment of the present invention. FIG. 10: Detector, 10A: Filament, 10
B: gas inlet, 10C: gas outlet, 10D: valve,
10E: Protection tube, 10F: Ejector, 10G:
Eject tube, 10H: valve, 10I: small hole.

Claims (1)

[Scope of utility model registration request] A protective cylinder with a small hole opened at the bottom that surrounds the filament disposed in the inner space, an eject mechanism that communicates with the lower part of the outer circumferential space of the protective cylinder and removes fluid containing dust, etc. The device is equipped with a means for heating the filament to a certain temperature, an amplifier connected to the filament by a lead wire, and a means for displaying the electrical signal amplified by the amplifier. A thermal conductivity type detector for gas chromatograph, characterized in that it is designed to discharge gas.