JP2858143B2 - Concentration analysis method and apparatus therefor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention uses a high-purity gas derived from a purification device or a high-purity gas filled in a container as a sample gas and contained in the gas. The present invention relates to a method and an apparatus for analyzing a trace amount of impurities (analyte) with high sensitivity by a concentration analysis method.

[Conventional technology]

The concentration analysis method comprises the steps of: adsorbing a component to be analyzed in a sample gas at a low temperature to an adsorbent in a concentrating tube controlled at a low temperature; concentrating the sample; and heating the concentrating tube while flowing a carrier gas through the concentrating tube. The component to be analyzed is desorbed and entrained in the carrier gas and introduced into the analyzer to measure the component to be analyzed.
The measurement unit is from ppm to ppb (1ppm = 1000ppb), and ppb
It is well adapted to the recent demand for microanalysis, which is progressing from ppt to 1ppb (1ppb = 1000ppt).

Hereinafter, a conventional concentration analysis method will be described with reference to FIG. 2 exemplifying a flow sheet of the conventional concentration analysis apparatus.

In the figure, L and M are hexagonal cocks configured so that the six flow paths can be simultaneously switched by operating the knob of the main body, and by switching to the solid line side, each port L _{1 to} L ₆ , M ₁
Communication as ~M ₆ is displayed by a solid line, also by switching to the broken line side is adapted to communicate as indicated by broken lines, each port _{L 1 ~L 6, M 1 ~M} 6 in various Gas sources and equipment are connected in series as shown in the figure.

That is, the port L ₁ of the hexagonal cock L receives a carrier gas source C filled with helium gas in a high-pressure vessel via the pressure reducing valve 1, and the port L ₃ receives a sample gas source S via the main valve 2. ,
The port L ₄ has a precision flow meter 3, the port L ₆ has a separation column 4 filled with a filler suitable for separating the analyte in the sample gas, and a detector 5 for detecting the analyte. Analyzers D are connected to each other.
M ₁ to the port L ₂ of hexagonal cock L, port M ₆ is respectively provided continuously to the port L ₅ of hexagonal cock L, concentration between 6 between the port M ₂ and Port M ₅ is, the port M ₃ are RenNarukei 7, a vacuum pump V through the main valve 8 is, to the port M ₄ blind cover 9 are respectively provided continuously.

The concentrating tube 6 is filled with an adsorbent appropriately selected so as to be able to adsorb 100% of the analyte in the sample gas at a low temperature equal to or lower than the adsorption temperature. The condensing tube 6 includes a cooling coil 6a and a heater 6b. Have.

Hereinafter, a conventional analysis method using this apparatus will be described in the order of steps.

First switching hexagonal cock L, and M in the solid lines, the pressure was reduced helium gas of the carrier gas source C to a predetermined pressure in the pressure reducing valve 1 as a carrier gas, port L ₁ of hexagonal cock L,
L ₂ , the ports M ₁ , M _{6 of} the hexagonal cock M and the ports L ₅ , L ₆ of the hexagonal cock L are again introduced into the analyzer D to keep the analysis system D in a stable state, and then to the exhaust meter 10. At the same time, the sample gas is exhausted from the main valve 2 to the exhaust system 10 via the ports L ₃ and L _{4 of} the hexagonal cock L and the flow meter 3.

Simultaneously with this state, the vacuum pump V is operated, and the main valve 8 and the ports M ₃ , M ₂ ,
Concentrated pipe 6, ports M _5, M _4, and stops after the elimination atmospheric components (oxygen and nitrogen) remaining in the piping leading to the blind cover 9.
(Standby Step) Next, cooling such as liquefied nitrogen is passed through the cooling coil 6a to cool the concentrating tube 6 to a predetermined temperature or lower. (Condenser tube cooling step) Then, while keeping the cooling step, both the hexagonal cocks L and M are switched to the broken line side, and the carrier gas is introduced into the analyzer D via the ports L ₁ and L ₆ and then exhausted to the exhaust system 10. At the same time, the sample gas is introduced into the concentration tube 6 through the ports L ₃ , L ₂ , M ₁ , and M _2, and the analyte in the sample gas is adsorbed at a low temperature on the adsorbent in the concentration tube 6, Air is exhausted to the exhaust system 10 through the ports M ₅ , M ₆ , L ₅ , L ₄ and the flow meter 3. (Concentration step) Next, the hexagonal cock M is switched to the solid line side while the hexagonal cock L is kept on the broken line side, and the vacuum pump V is restarted. Is stopped after discharging the main components of through the ports M ₂ and M ₃ . (Main component discharging step) Next, the heating heater 6b is operated to heat the concentrating tube 6, and the analyte to be analyzed which has been low-temperature adsorbed in the concentrating tube 6 is desorbed.
The hexagonal cock L is switched to the solid line side, and the hexagonal cock M is switched to the dashed line side, and the carrier gas flows through the ports L ₁ , L ₂ , M ₁ , M ₂ to the concentrating tube 6 to entrain the components to be analyzed with the carrier gas. Then, it is introduced into the analyzer D via the ports M ₅ , M ₆ , L ₅ , L ₆ . As a result, the components to be analyzed are each separated by the separation column 4 and sequentially introduced into the detector 5, and the concentration is determined from the detection value of the detector 5 and the amount of the sample gas measured by the flow meter 3 during the concentration step. Quantified. (Analysis Step) [Problems to be Solved by the Invention] However, in the conventional method, even in the standby step, the atmosphere in the reservoir such as the combined meter 7 and the blind lid 9 of the piping system including the concentrating pipe 6 can be obtained even by evacuation during the standby step. Since the components remain without being discharged, they are adsorbed by the adsorbent in the concentration tube 6 during the concentration step, are later desorbed and are measured by the analyzer D, and the main component discharge step is performed by evacuation, and By opening and closing the six-way cocks L and M frequently, the atmospheric components are mainly the six-way cocks L and M.
The background becomes large due to a slight intrusion through the sheet portion or the like, and it has been difficult to accurately measure the concentration at the level of ppb or less.

In the analysis step, since the analyte is desorbed by heating the concentration tube 6, a carrier gas flows through the concentration tube 6 to cause the analyte to accompany the carrier gas. The total amount of the components to be analyzed cannot be introduced into the analyzer D due to the stagnation in the system of the vacuum pump V, and the main components that have not been desorbed in the main component discharge step are desorbed by heating, and thereby the concentrating tube system , And a part of the analyte component may leak to the atmosphere together with the main component, making accurate measurement difficult.

An object of the present invention is to provide a concentration analysis method and an apparatus thereof for solving such a disadvantage.

[Means for solving the problem]

In order to achieve the above object, the concentration analysis method of the present invention comprises a standby step in which a carrier gas is circulated through a concentration pipe and then exhausted through an analysis system; a concentration pipe cooling step of cooling the concentration pipe to a predetermined temperature or lower; Is introduced into the analyzer without passing through the concentrating tube and then exhausted, and the sample gas is circulated through the concentrating tube so that the components to be analyzed in the sample gas are adsorbed on the adsorbent in the concentrating tube at low temperature and then discharged. A main component discharging step in which the carrier gas is passed through a concentrating tube, a main component adsorbed at a low temperature together with a component to be analyzed in the concentrating process is introduced into the analyzer together with the analyte, and then discharged. Characterized by sequentially performing an analysis step of heating the concentrator tube to a predetermined temperature or higher, desorbing the analyte to be adsorbed at a low temperature on the concentrator tube, and accompanying the carrier gas to introduce it into the analyzer, In addition, the Agasu is characterized by being supplied via a purifier, further characterized by performing a channel switching of the carrier gas and the sample gas seal with multi-way cock.

In addition, the concentration analyzer of the present invention includes, at each port of the multi-way cock, a carrier gas pipe connected to the carrier gas source, a sample gas pipe connected to the sample gas source, a cooling unit and a heating unit. A concentrator tube inlet line and a concentrator tube outlet line connected to the inlet and outlet of the concentrator tube,
An analysis pipe line connected to the analyzer and a flow measurement pipe line connected to the flow meter are respectively connected, and the multi-way cock has at least a path for introducing the carrier gas into the concentration meter after flowing through the concentration pipe. And a path for introducing the carrier gas into the analyzer without passing through the concentration pipe, and a path for introducing the sample gas into the flow meter after flowing through the concentration pipe.

(Operation)

ADVANTAGE OF THE INVENTION According to the method and apparatus of this invention, since the elimination of the atmospheric component of a concentrating tube system in a standby process is performed by flowing a carrier gas into a concentrating tube, it can be reliably excluded.

In addition, since the elimination of the main component in the main component discharging step is performed by flowing a carrier gas into the concentrating tube, the elimination of the main component can be performed more efficiently than performing the elimination of the main component by vacuum evacuation, and the rapid pressure due to the desorption of the main component can be achieved. It is possible to prevent the analyte from leaking by suppressing the rise. Further, since the main component is sent to the analyzer along with the carrier gas, the switching operation of the cock can be reduced, and the intrusion of atmospheric components can be greatly reduced. In the analysis step, the concentration tube is heated in the state of the main component discharge step to desorb the analyte, so that the entire amount of the analyte is introduced into the analyzer together with the carrier gas.

As described above, according to the method of the present invention, the conventional vacuum evacuation is unnecessary, and the apparatus configuration is simplified, and the invasion of atmospheric components is more effectively prevented. Will be possible.

Next, as described above, the carrier gas is usually used after being filled in the high-pressure container, so that the carrier gas is used under reduced pressure through the pressure reducing valve. Atmospheric components enter when passing through the valve. Therefore, even if the gas in the high-pressure vessel is of extremely high purity, it is partially contaminated when passing through the pressure reducing valve, so that the carrier gas after passing through the reduced pressure is passed through a purifier to remove impurities in the carrier gas in advance. By doing so, even if the carrier gas flows together with the sample gas into the concentration tube controlled at a low temperature during the concentration step, the impurities in the carrier gas are extremely reduced, so that the carrier gas can be adsorbed at a low temperature by the adsorbent in the concentration tube. Almost no background during measurement can be further reduced, and sensitivity can be further improved.

Further, when the flow path switching between the carrier gas and the sample gas is performed by a multi-way cock with a seal, it is possible to prevent the intrusion of the atmosphere into the cock when the flow path is switched by operating the cock, which is effective in improving the sensitivity. is there.

In particular, when both the purifier and the multi-way cock with seal are used in combination, the carrier gas containing no impurities flows through the concentrating tube while being clean, so that the impurities in the carrier gas are not concentrated in the concentrating tube and the sensitivity is improved. Extremely effective.

〔Example〕

FIG. 1 is a flow sheet of an apparatus according to an embodiment of the present invention, in which the same elements as those in FIG. 2 are denoted by the same reference numerals.

The device of the present embodiment is a device for each port E _{1 of a} hexagonal cock E with a seal.
To to E _6, and the carrier gas conduit 11 connected to the carrier gas source C, the sample gas line 12 connected to the sample gas source S,
A concentrating tube introducing line 13 and a concentrating tube deriving line 14, which are respectively connected to the inlet and outlet of the concentrating tube 6 having a cooling coil 6a as a cooling means and a heater 6b as a heating means,
An analysis pipe 15 connected to the analyzer D and a flow measurement pipe 16 connected to the flow meter 3 are connected to each other.
The carrier gas pipe 11 is provided with a purifier 20 for removing impurity components in the carrier gas.

This hexagonal cock E with a seal hermetically covers the internal switching flow path with a casing E _C and introduces a gas equivalent to a carrier gas into a space formed between the casing E _C and the switching flow path. 21, the air is circulated through the outlet pipe 22, so that the invasion of the atmosphere can be more completely prevented.

Further, the purifier 20 is configured by filling an adsorbent such as molecular sieves, activated carbon and the like in an appropriate airtight container having a carrier gas introduction / extraction section and providing a cooling means (not shown). This is to remove impurities.

Normally, in the case of microanalysis as the object of the present invention, since the carrier gas is of high purity, the carrier gas of the carrier gas source C contains almost no impurities. Since the carrier gas is usually filled at a high pressure in a high-pressure container such as a cylinder, the carrier gas is used by reducing the pressure to a predetermined pressure using the pressure reducing valve 1. Then, when the carrier gas passes through the pressure reducing valve 1, the atmosphere enters, so that impurities due to this are removed.

Since the pressure of the carrier gas after passing through the pressure reducing valve is higher than the atmospheric pressure, it is generally considered that the atmosphere does not enter.However, in the measurement at ppb or less, the measured values were obtained with and without the purifier. It was found that even if the carrier gas was depressurized at a pressure higher than the atmospheric pressure, the air slightly penetrated. Furthermore,
Comparing the pressure reducing valve 1 with a normal gate valve such as the main valve 2 of the sample gas source S, the pressure reducing valve 1 has a greater degree of invasion of the atmosphere. This is because the pressure reducing valve 1 has a pressure reducing mechanism. It is presumed that this is because of the complicated structure and the mechanical operation of the pressure reducing mechanism.

Next, a description will be given of an operation method of the embodiment apparatus configured as described above. First, the six-way cock E is set to the solid line side, a carrier gas is introduced into the purifier 20 through the pressure reducing valve 1, and impurities in the carrier gas are removed. After removing the port
The gas is introduced into the analyzer D via E ₁ , E ₂ , the concentration tube 6, and the ports E ₅ and E ₆ , and is discharged to the exhaust system 10 after the analyzer D is maintained in a stable state. On the other hand, the sample gas flows from the main valve 2 to the flow meter 3 via the ports E ₃ and E _4, and then is discharged to purge the system.
(Standby Step) Next, in the state of the above-described standby step, cooling such as liquefied nitrogen is passed through the cooling coil 6a to cool the concentrating tube 6 to a predetermined temperature. (Condenser tube cooling step) Next, the hexagonal cock E is switched to the broken line side, the carrier gas is introduced into the analyzer D through the ports E ₁ and E ₆ , and the sample gas is introduced through the ports E ₃ and E ₂ . After the analyte in the sample gas is adsorbed on the adsorbent in the concentrating tube 6 at low temperature, it is discharged from the exhaust system 10 through the ports E ₅ and E ₄ and the flow meter 3. I do. (Concentration Step) Next, the six-way cock E is switched to the solid line side again, and the carrier gas is introduced into the concentration tube 6 as described above, and the adsorbed main component is desorbed together with the analyte, and is introduced into the analyzer.
(Main component discharging step) After a predetermined time, the heater 6b is operated to heat the concentrating tube 6 to a predetermined temperature or more, and the analyte to be adsorbed on the concentrating tube 6 in the concentrating step is entrained with the carrier gas and is ported It is introduced into the analyzer D via E ₅ and E ₆ . As a result, the components to be analyzed are each separated in the separation column 4 and sequentially introduced into the detector 5, and the detected value from the detector 5 and the flow meter 3 during the concentration step are used.
The concentration is determined from the sample gas amount measured by the above.
Note that the sample gas is discharged to the exhaust system 10 in the same manner as in the standby step. (Analysis Step) The concentration analysis method according to the present invention is carried out as described above. Table 1 shows a comparison of the cock switching operation with the conventional method. In the table, [-] indicates switching to the solid line side, [...] indicates switching to the broken line side, and "↓" indicates switching operation.

As is clear from the above Table 1, the conventional method measures by switching the cock five times, whereas the method of the present invention can measure by two switching operations.

Next, the measurement limits of the case where impurities are measured using the apparatus of the embodiment of FIG. 1 using high-purity hydrogen gas as a sample gas and the case where measurement is performed using the conventional apparatus illustrated in FIG. 2 will be compared. An experiment was performed. In the measurement using the example apparatus,
The case where the purifier 20 was used, the case where it was not used, and the case where the cock E with a seal was used and the case where a normal hexagonal cock were used were compared.

A thermal conductivity detector was used as the detector 5, a purifier 20 was a column having an inner diameter of 4 mm and a length of 1 m filled with molecular sieves 5A, and a concentrating tube 6 was an inner diameter of 3 mm and a length of 150 mm.
Each column was filled with porous polymer beads, and each was cooled to −185 ° C. or lower with liquefied nitrogen. The heating of the concentrating tube 6 after concentration was performed by a heater wound around the concentrating tube 6, and the temperature was raised at a rate of 150 ° C. per minute. Table 2 shows the results of this experiment.

As is clear from Table 2, according to the method of the present invention, it is possible to measure with higher sensitivity than before, without using both the purifier 20 and the cock E with a seal. It can be seen that the sensitivity can be further improved by using one of them, and the sensitivity can be further improved by using both.

〔The invention's effect〕

As described above, according to the present invention, since the concentrating tube is cooled while flowing the carrier gas into the concentrating tube, the invasion of the atmosphere can be prevented, and the concentration analysis can be performed with higher precision than before, and The piping system can be simplified.

In addition, since conventional vacuum evacuation is not required, the apparatus configuration is simplified, and the intrusion of atmospheric components is more effectively prevented, so that the background can be reduced compared to the conventional art, and high-sensitivity measurement can be performed.

In particular, the carrier gas before flowing through the concentrating tube is passed through a purifier to remove impurities in the carrier gas, or the measurement sensitivity can be solidified by using a sealed multi-way cock. Further, highly sensitive measurement becomes possible.

[Brief description of the drawings]

FIG. 1 is a flow sheet of a concentration analyzer showing one embodiment of the present invention, and FIG. 2 is a flow sheet of a conventional concentration analyzer. C: carrier gas source, D: analyzer, E: hexagonal cock with seal, S: sample gas source, 3: flow meter, 6:
Concentrator tube, 20 …… Purifier

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-49-48392 (JP, A) JP-A-52-88088 (JP, A) JP-A-1-265157 (JP, A) 156101 (JP, U) Japanese Utility Model 60-83957 (JP, U) Japanese Utility Model 60-31663 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01N 1/22 G01N 1 / 28

Claims (4)

(57) [Claims] 1. A standby step in which a carrier gas is circulated through a concentrating tube and then exhausted through an analyzer, a condensing tube cooling step in which the condensing tube is cooled to a predetermined temperature or lower, and the carrier gas is supplied without passing through the concentrating tube. A concentration step of exhausting the gas after being introduced into the analyzer, flowing the sample gas through the concentrating tube, adsorbing the analyte in the sample gas at a low temperature to the adsorbent in the concentrating tube, and discharging the sample gas; A main component discharging step in which the main component adsorbed at a low temperature together with the component to be analyzed in the concentrating step is introduced into the analyzer and discharged after the concentrating step. A desorption step of desorbing the analyte adsorbed at a low temperature on the concentrating tube and accompanying the carrier gas to introduce the analyte into a spectrometer. 2. The method according to claim 1, wherein the carrier gas is supplied via a purifier. 3. The concentration analysis method according to claim 1, wherein the flow path of the carrier gas and the sample gas is switched by a multi-way cock with a seal. 4. Introducing, into each port of the multi-way cock, a carrier gas line connected to a carrier gas source, a sample gas line connected to a sample gas source, and a concentration tube provided with cooling means and heating means. Concentrator tube introduction line and concentrator tube outlet line connected to the section and the outlet section, respectively, and an analysis line connected to the analyzer and a flow rate measurement line connected to the flow meter, respectively, The multi-way cock has at least a path for introducing the carrier gas into the analyzer after flowing through the concentrating tube, a path for introducing the carrier gas into the analyzer without passing through the concentrating tube, and a method for flowing the sample gas through the concentrating tube. A concentration analyzer characterized by being provided so that a path to be introduced into a flow meter can be switched.