JPS6230587B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention uses a carrier gas to separate a certain amount of sample collected by a sampling valve into a column (column) installed apart from the sampling valve.
The present invention relates to a collection sample transfer conduit for a gas chromatograph for transfer to a detection section.

FIG. 1 shows a typical configuration example of a gas chromatograph. The sample S is flowed through a sampling valve 1 and a measuring tube 1a attached to the sampling valve 1,
When sampling valve 1 is switched, measuring tube 1a
A certain amount (for example, 1 ml) of the sample collected in the sample is transferred by the carrier gas C through the conduit 5 to the separation section (column) 2, where the sample is separated into each component, and each component is sent to the detection section, e.g. A thermal conductivity type detector 3 sequentially detects the amount of each component.

In order to install the sampling valve 1 away from the separation section 2 and near the sample outlet, as shown in FIG. Store 1. This is known as a so-called remote sampling method. In this system, a certain amount of sample is collected by a sampling valve 1 and sent by a carrier gas C through a conduit 5 to a separating section 2 and a detecting section 3 housed in a thermostatic chamber 4. The conduit 5 is usually a thin tube made of stainless steel,
For example, one with an outer diameter of 2 mm and an inner diameter of 1 mm is used. The length of this conduit 5 typically amounts to 10 to 30 m.

When measuring adsorbent components such as moisture in a sample using this remote sampling method,
Moisture is adsorbed on the inner wall of the stainless steel tube that is the conduit 5, which widens the width of the moisture peak and degrades peak measurement accuracy. In addition, the degree of moisture adsorption on the inner wall of the stainless steel tube that serves as the conduit 5 is significantly affected by the temperature of the tube, so unless the tube temperature is precisely controlled to a constant value with an accuracy of, for example, ±0.1℃, the moisture peak Outflow time (retention time) is unstable. Incidentally, the stainless steel pipe portion that serves as the conduit 5 is normally heated and kept warm with steam, but the temperature fluctuation range is thought to be 20°C or more.

On the other hand, in order to prevent moisture from being adsorbed to the conduit 5,
It is known to use a tube of non-adsorptive resin such as tetrafluoroethylene or hexafluoropropylene as the conduit 5. However, this resin tube has the property of allowing gas to permeate through the tube wall, so if the length of the conduit 5 is long and the surface area is large, air in contact with the outer wall of the tube will penetrate into the tube.
Mixed with carrier gas. As a result, the measurement sensitivity changes and the detection output baseline fluctuates depending on the amount of air mixed in.

SUMMARY OF THE INVENTION An object of the present invention is to provide a collection sample transfer conduit that allows correct measurement of the component to be detected.

According to this invention, the transfer conduit is a double pipe, and its inner conduit is made of a resin material that does not easily react with or adsorb the component to be measured in the sample. On the other hand, the external conduit is made of metal or the same type of resin material as the internal conduit. Further, the space between the inner conduit and the outer conduit is filled with a carrier gas or a gas having approximately the same thermal conductivity as the carrier gas. For example, the gas may be flowed or filled between the inner and outer conduits.

FIG. 3 shows an embodiment of the collected sample transfer device according to the present invention, in which parts corresponding to those in FIG. 2 are given the same reference numerals. According to the invention, an external conduit 6 is provided outside the conduit 5 to form a double conduit. The internal conduit 5 is made of a resin material that does not easily react with or adsorb the component to be detected in the sample, such as a fluorine-based resin such as tetrafluoroethylene or hexafluoropolypropylene, or a chemical material such as polyethylene or polypropylene. Constructed of resin that is inert to objects. The external conduit 6 may be made of a metal such as stainless steel or copper, or the same type of resin as the internal conduit 5, or any other material, but generally this transfer conduit must be heated and kept warm. It is said to be heat resistant and can withstand that temperature.

The space between the internal conduit 5 and the external conduit 6 is filled with carrier gas C or a gas having approximately the same thermal conductivity as carrier gas C. For example, in FIG. 3, such a gas 7 is supplied to an air inlet 8 between the inner conduit 5 and the outer conduit 6 at the end on the side of the separation section 2, and to an exhaust port 9 at the end on the side of the sampling valve 1. More is discharged to the outside.

When carrier gas C is used as gas 7,
For example, as shown in FIG. 4, a carrier gas that is provided as a reference gas in a hot wire bridge constituting the thermal conductivity type detector of the detection section 3 and has passed through this bridge is supplied to the air supply port 8.

Since the gas 7 flowing between the internal conduit 5 and the external conduit 6 is hardly contaminated by the sample, the carrier gas C is supplied to the air supply port 8 as shown in FIG. 5, and the carrier gas from the exhaust port 9 is passed through the sampling valve 1. It may also be supplied to Furthermore, as shown in FIG. 6, the carrier gas supplied to the air supply port 8 may be branched and supplied as a reference gas to the hot wire bridge of the detection section 9 through the flow rate adjustment column 11.

When a hot wire bridge is used in the detection unit 3 and helium gas is used as the carrier gas C, hydrogen gas having a thermal conductivity value close to that of helium gas may be used as the gas 7 filling the space between the internal conduit 5 and the external conduit 6. . In this case, even if this gas 7 enters the conduit 5 through the wall of the internal conduit 5 and is mixed with the carrier gas, the detection sensitivity and baseline of the detection section 3 are hardly affected. In this case, it is assumed that hydrogen does not exist among the components to be detected in the collected sample.

The gas 7 between the internal conduit 5 and the external conduit 6 may be sealed without being allowed to flow.

According to the configuration described above, when measuring moisture in a sample, since there is almost no adsorption to the conduit 5 when the collected sample passes through the conduit 5, the shape of the detected moisture peak may be disturbed. Therefore, peak measurements can be performed accurately. Also, conduit 5
Since the atmosphere in contact with the outer periphery of the tube is a carrier gas or an equivalent gas, even if this gas penetrates the wall of the conduit 5, the carrier gas inside the conduit 5 will not be affected, and there will be no change in the sensitivity of the detected component or a change in the baseline. There is no risk of fluctuations. When a carrier gas is used as the gas 7, there is no need to use a special gas. Furthermore, compared to the case where carrier gas is used separately for sample transfer and as gas 7 for preventing incorporation of outside air, the consumption amount of carrier gas can be reduced in FIGS. 4 to 6. Furthermore, the piping between the sampling valve 1 and the separation section 2 only needs to be a single double pipe, which simplifies the piping.

Note that this invention is applicable not only to the measurement of moisture in a sample, but also to the measurement of hydrogen sulfide, ammonia, and other components.

[Brief explanation of the drawing]

Figure 1 shows the general configuration of a conventional gas chromatograph, Figure 2 shows the configuration of a conventional remote sampling type gas chromatograph, and Figure 3 shows an example of the sample transfer conduit according to the present invention. 4 to 6 are diagrams showing the configuration of a remote sampling type gas chromatograph to which other examples of the collection sample transfer conduit according to the present invention are applied. 1... Sampling valve, 2... Separation section, 3
...Detection section, 4, 4a... Constant temperature chamber, 5... Internal conduit, 6... External conduit, 7... Gas.

Claims (1)

[Claims] 1 A conduit that transports a certain amount of sample collected by a sampling valve to a thermal conductivity type separation detection section using a carrier gas, and this conduit is made of resin that is unlikely to react or adsorb with the target components contained in the sample. an internal conduit consisting of an internal conduit, an external conduit provided over almost the entire length to accommodate the internal conduit, and the carrier gas filled between the internal conduit and the external conduit, or the carrier gas having a thermal conductivity and A collection sample transfer conduit for a gas chromatograph comprising a gas having approximately the same temperature.