JP2011106873A - Pretreatment apparatus for elemental analysis, and elemental analyzer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pretreatment device for elemental analysis preventing air from mixing, markedly reducing variation, and improving analytical capability in elemental analysis by an elemental analyzer, even if a trace amount of sample is used. <P>SOLUTION: The pretreatment device for elemental analysis 2 includes a sample-holding member 11, a valve 12 for sample introduction, an oxidation tube 13, a reduction tube 14, a reaction gas feed means 15, a carrier gas feed means 16, a switching valve 17, which feeds a reaction gas and carrier gas switched to the oxidation tube 13, and a gas chromatograph 3. The pretreatment apparatus includes a moisture trap 18, which removes moisture (H2O) in sample gas which passes through the reduction tube 14. The sample gas passing through the moisture trap 18 is separated by the gas chromatograph 3 and is sent to an analyzer 5. The switching valve 17 is provided inside a chamber 19. The chamber 19 introduces an inert gas (He or Ar) as a purge gas which is fed from a purge gas feed means 22. Mixing of air from the switching valve 17 can be intercepted. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  In the present invention, a sample is burned at a high temperature to obtain a sample gas containing carbon dioxide and nitrogen oxide, and the sample gas is conveyed by a carrier gas to oxidize, reduce and remove moisture, and then carbon dioxide and nitrogen are removed. The present invention relates to a pretreatment device for elemental analysis and an elemental analysis device that are separated into gases.

  When measuring the stable isotope ratio of organic carbon and nitrogen contained in sediments, plankton and other animals and plants deposited on the seabed (hereinafter referred to as carbon / nitrogen stable isotope ratio measurement) It is possible to know the past global environmental change estimation and future prediction, elucidation of material circulation, animal and plant production pathways, biological nutritional status, etc.

  For this reason, elemental analyzers such as devices for measuring carbon and nitrogen stable isotope ratios have been developed. The carbon / nitrogen stable isotope ratio measurement apparatus generally includes a mass spectrometer for measuring the carbon and nitrogen stable isotope ratio of a sample substance, and a sample for preparing a sample to be sent to the mass spectrometer. A processing device, that is, a pretreatment device for elemental analysis (also referred to as a flash elemental analyzer) is provided.

  A conventional elemental analysis pretreatment apparatus includes an autosampler that supplies a sample, an oxidation tube, a reduction tube, a reaction gas supply unit, and a carrier gas supply unit. The oxidation tube burns the sample supplied from the autosampler to the combustion section with a reaction gas (oxygen gas) to generate a sample gas, and passes the sample gas through the oxidation section to oxidize with the oxidizing agent. The reduction tube is connected to the oxidation tube and reduces nitrogen oxide in the sample gas to nitrogen gas. The reactive gas supply means supplies a reactive gas for burning the sample to the combustion section of the oxidation tube. The carrier gas supply means supplies a carrier gas for transporting the sample gas to the oxidation and reduction and moisture removal means to the combustion section of the oxidation tube.

Organic matter such as sediment deposited on the seabed and plants and animals such as plankton generally has a nitrogen: carbon ratio of about 1:10, and the ratio of nitrogen is small. When this organic matter (sample) is small, nitrogen is particularly small. Therefore, according to the conventional pretreatment device for elemental analysis, even if you want to measure the stable isotope ratio of carbon and nitrogen with the elemental analyzer, measure it. According to the pretreatment device for elemental analysis described in Patent Document 1, the cross-sectional area of the combustion section in the oxidation tube was made larger than the cross-sectional area of the downstream oxidation column section. Can improve the detection ability of elements such as carbon and nitrogen, and can accurately measure the stable isotope ratio of carbon and nitrogen, mass analysis of each elemental component, etc. even with a small amount of sample It became so. For example, even if the sample weighs less than about 50 μg, the detection intensity (gas amount) of the carbon component and nitrogen component detected by the elemental analyzer can be increased, and the response curve (chromatogram) can also be greatly increased.・ Precise measurement of nitrogen stable isotope ratio is now possible.

JP 2008-70134 A

  However, even in the pretreatment device for elemental analysis described in Patent Document 1, since the measurement value varies, further improvement in the analysis capability of the element component that does not cause variation is necessary.

  The present inventors have earnestly studied that variations occur in the measured values. As a result, attention was paid to the fact that the practical apparatus according to the pretreatment apparatus for elemental analysis described in Patent Document 1 has the following structure.

  Although not described in Patent Document 1, in a practical apparatus, an autosampler and an oxidation tube are connected via a sample introduction opening / closing valve. A reaction gas (oxygen gas) supply pipe supplied from an oxygen gas cylinder and a carrier gas (He gas) supply pipe supplied from a helium gas cylinder are connected to two input ports of the electromagnetic three-way valve. Furthermore, the remaining one output port of the electromagnetic three-way valve is connected to the downstream (oxidation tube side) passage of the on-off valve for sample introduction by a supply pipe. According to this practical apparatus, the reaction gas and the carrier gas (He gas) are alternatively supplied to the oxidation tube by switching the electromagnetic three-way valve. Further, a carrier gas (He gas) supplied from a helium gas cylinder is constantly supplied as a purge gas for the autosampler to the upstream (autosampler side) passage of the sample introduction opening / closing valve.

  The cause of the variation in the measured value was that a small amount of air was mixed from the electromagnetic three-way valve. If even a small amount of air is mixed in from the valve housing of the electromagnetic three-way valve, the air will be introduced into the oxidation tube together with the carrier gas, and the minute amount of nitrogen, which is a component of the air, will affect the measured value each time. It is done. The present inventors thought that the purge gas does not function sufficiently because the carrier gas (He gas) is used as the purge gas for the autosampler, and the air in the autosampler cannot be completely expelled. That is, air heavier than the purge gas remains in the concave portion of the valve body of the sample introduction on-off valve. When the sample introduction on-off valve opens and supplies the sample from the autosampler to the oxidation tube, Residual air in the recess of the valve body of the on-off valve enters the oxidation tube. For this reason, it was thought that nitrogen, which is a constituent of air, might affect the measured values each time.

  The present invention has been devised in view of the above points, and even when the amount of sample is extremely small by eliminating air in the oxidation tube, the variation in the analysis of elemental components in the elemental analyzer is drastically reduced. It is an object of the present invention to provide a pretreatment device for elemental analysis capable of improving analytical ability and to provide an elemental analysis device provided with the pretreatment device for elemental analysis.

  In order to achieve the above object, a pretreatment device for elemental analysis according to the present invention includes a sample holding member that supplies a sample through an open / close valve for introducing a sample while the sample is purged with a purge gas. Connected to the on-off valve, the sample supplied from the sample holding member is burned to generate a sample gas, and an oxidation tube that oxidizes the sample gas is connected to the oxidation tube, and nitrogen in the sample gas A reducing pipe for reducing the oxide to nitrogen gas; a reactive gas supplying means for supplying a reactive gas for burning the sample; a carrier gas supplying means for supplying a carrier gas for transporting the sample gas to the reducing means; and a reactive gas And a gas chromatograph that separates the generated gas, and a switching body is provided with a valve housing inside the chamber and a valve body. An actuator to be driven is provided outside the chamber, and the chamber introduces helium gas or argon gas, which is an inert gas different from the carrier gas, as a purge gas, and selectively supplies it from the switching valve to the oxidation tube It is characterized by having a function of blocking the mixing of air into the gas or carrier gas.

  According to the above configuration, when the pretreatment device of Patent Document 1 is used in the analysis means connected to the gas chromatography even if the amount of the sample is very small by eliminating air from the switching valve. Compared with, the variation is drastically reduced, and the elemental component can be analyzed more accurately.

  In order to achieve the above object, a pretreatment device for elemental analysis according to the present invention includes a sample holding member that supplies a sample through an open / close valve for introducing a sample while the sample is purged with a purge gas. Connected to the on-off valve, the sample supplied from the sample holding member is burned to generate a sample gas, and an oxidation tube that oxidizes the sample gas is connected to the oxidation tube, and nitrogen in the sample gas A reducing pipe for reducing the oxide to nitrogen gas; a reactive gas supplying means for supplying a reactive gas for burning the sample; a carrier gas supplying means for supplying a carrier gas for transporting the sample gas to the reducing means; and a reactive gas And a gas chromatograph that separates the generated gas, and a switching body is provided with a valve housing inside the chamber and a valve body. The actuator to be driven is provided outside the chamber, and the chamber is introduced with helium gas or argon gas, which is an inert gas different from the carrier gas, as a purge gas, and alternatively supplied from the switching valve to the oxidation tube The gas or carrier gas is configured to block air from being mixed, and the reactive gas or carrier gas is introduced as a purge gas for the sample holding member upstream of the sample introduction opening / closing valve via the switching valve. It is characterized by having a function.

  According to the above configuration, by eliminating air contamination from the switching valve and eliminating air contamination from the sample holding member, even in a very small amount of sample, in the analysis means connected to the gas chromatography, Compared with the case where the pretreatment apparatus of Patent Document 1 is used, the variation is greatly reduced, and the elemental component can be analyzed more accurately.

  In order to achieve the above object, an elemental analysis apparatus of the present invention comprises any one of the elemental analysis pretreatment apparatuses and an analysis means connected to the elemental analysis pretreatment apparatus.

  According to the above configuration, the sample is very small by eliminating the air from the switching valve or by eliminating the air from the switching valve and the air from the sample holding member. However, when measuring the stable isotope ratio of carbon and nitrogen, mass spectrometry of each elemental component, etc., the variation is drastically reduced as compared with the case where the pretreatment device of Patent Document 1 is used, Elemental components can be analyzed more accurately.

  According to the present invention, an element capable of dramatically reducing variation in the analysis of elemental components in the elemental analysis apparatus and improving the analysis ability even if the sample is extremely small by eliminating air mixing into the oxidation tube. An analytical pretreatment device can be provided. Moreover, the elemental analyzer provided with this elemental analysis pretreatment apparatus can be provided.

1 is a schematic front view showing an elemental analyzer according to a first embodiment of the present invention. It is a principal part enlarged view of FIG. It is a principal part front view which shows the other operation state of the apparatus of FIG. It is a principal part enlarged view of FIG. It is a time chart of the output of the control signal of the controller of the apparatus of FIG. FIG. 6 is a distribution graph showing the measurement result of nitrogen stable isotope ratio according to the result of elemental analysis of Example 1. FIG.

  Hereinafter, a pretreatment device for element analysis and an element analysis device according to an embodiment of the present invention will be described with reference to the drawings.

The sample is, for example, a very small amount of a natural substance (organic compound) composed of sediments deposited on the seabed or plants and animals such as plankton. Carbon ( ¹² C, ¹³ C) and nitrogen ( ¹⁴ N, ¹⁵ N ). The sample has a small weight of about 1 to 10 μg and is enclosed in a capsule formed of tin foil.
[Outline of configuration of pretreatment equipment for elemental analysis and elemental analysis equipment]
In FIG. 1, an element analyzer 1 is an apparatus for analyzing elements contained in a small amount of sample, includes an element analysis pretreatment device 2, and a sample gas generated by the element analysis pretreatment device 2. Is composed of an open split 4 that separates into a measurement gas of a component for elemental analysis, and an analysis means 5 that analyzes the elemental component of the measurement gas.

The elemental analyzer 1 is a measuring device for measuring the carbon / nitrogen stable isotope ratio of carbon ( ¹² C, ¹³ C) and nitrogen ( ¹⁴ N, ¹⁵ N) generated from a small amount of sample, for example. . In order to measure the stable isotope ratio of the elements (C, N) contained in the sample in the analysis means 5, it is necessary that each element is gas (CO ₂ , N ₂ ) in advance. The device for gasifying the sample is the pretreatment device 2 for elemental analysis.

This elemental analyzer 1 is, for example, a mass spectrometer for measuring the carbon / nitrogen stable isotope ratio of carbon ( ¹² C, ¹³ C) and nitrogen ( ¹⁴ N, ¹⁵ N) generated from a small amount of sample. And carbon / nitrogen stable isotope ratio measuring device.

The element analysis pretreatment apparatus 2 is a component excluding the open split 4 and the analysis means 5. In order to measure the stable isotope ratio of the elements (C, N) contained in the sample by the analyzing means 5, it is necessary that each element is gas (CO ₂ , N ₂ ) in advance. For this purpose, the element analysis pretreatment apparatus 2 is an apparatus for gasifying a sample into a gas to be measured (gas sample) of each analysis component. The pretreatment device 2 for elemental analysis burns a sample with a reaction gas (= oxygen (O ₂ )) to gasify it, oxidizes the gasified sample gas (CO ₂ , NO ₂ ), and reduces NO _2. Nitrogen gas (N ₂ ), moisture (H ₂ O) is removed, and the gas to be measured is a mixed gas of carbon dioxide gas (CO ₂ ) and nitrogen gas (N ₂ ). In this device, the gas to be measured is separated into carbon dioxide gas (CO ₂ ) and nitrogen gas (N ₂ ) components and sent to the open split 4.
[First Embodiment]
In this embodiment, a case where the present invention is applied to a carbon / nitrogen stable isotope ratio measurement apparatus is shown.

In the following, the basic components are outlined, then the feature components are described in detail, followed by a brief description of the other components, but there is no explanation for either because the inventor is partially identical. It is assumed that the configuration of the part is the same as that of Patent Document 1 described in detail. For example, the configuration of the autosampler is the same as that of the patent document 1 except for supply of purge gas.
[Outline of basic components]
As shown in FIG. 1, the elemental analysis device 1 includes a pretreatment device 2 for elemental analysis and a measurement gas for measuring the sample gas (mixed gas of (CO ₂ ) and (N ₂ )) that has passed through the moisture trap 18. A gas chromatograph 3 that separates into (CO ₂ ) and (N ₂ ) components, an open split 4, and an analysis means 5 are provided.

  As shown in FIG. 1, the element analysis pretreatment apparatus 2 includes an autosampler 11, a sample introduction opening / closing valve 12, an oxidation tube 13, a reduction tube 14, a reaction gas supply means 15, and a carrier gas supply means. 16, a switching valve 17 that alternatively supplies a reaction gas and a carrier gas to the oxidation pipe 13, a purge gas supply means 22, a mass flow controller 23 that adjusts the supply amount of the carrier gas, and a supply amount of the reaction gas A mass flow controller 24.

In the element analysis pretreatment apparatus 2, the autosampler 11 for supplying the sample M is connected to the oxidation pipe 13 via the sample introduction opening / closing valve 12, and the reduction pipe 14 is connected to the downstream end of the oxidation pipe 13. ing. The reaction gas (oxygen) supplied from the reaction gas supply means 15 and the carrier gas (inert gas) supplied from the carrier gas supply means 16 are introduced into the switching valve 17. By switching the switching valve 17, the reaction gas and the carrier gas are alternatively supplied to the oxidation tube 13. The element analysis pretreatment apparatus 2 includes a moisture trap 18 that removes moisture (H ₂ O) in the sample gas that has passed through the reduction tube 14. The sample gas (mixed gas of (CO ₂ ) and (N ₂ )) that has passed through the moisture trap 18 is sent to the gas chromatograph 3. The functions of these components are the same as those in Patent Document 1.

  The autosampler 11 accommodates the sample M in a state where the inside is purged with a purge gas. The sample M is supplied from the autosampler 11 to the oxidation tube 13 through the sample introduction opening / closing valve 12. The sample introduction opening / closing valve 12 includes a valve housing 12a and a valve body 12b.

  The valve housing 12a has a transparent cover plate on the front surface, and has a structure in which the inside of the valve can be seen through the cover plate. The valve body 12b has, for example, a U-shaped recess, and when the U-shaped recess is upward, the sample M supplied from the autosampler 11 is accommodated in the U-shaped recess. This is a configuration in which the sample M is dropped into the oxidation tube 13 with the U-shaped recess turned downward by rotating the angle. Thereafter, the valve body 12b rotates 180 degrees and stops at a position where the U-shaped concave portion faces upward, and the sample M to be supplied next from the autosampler 11 is accommodated. A drive source for reciprocatingly rotating the valve body 12b by 180 degrees is performed by a servo motor 11a that intermittently rotates a sample feed table of an autosampler 11 described later.

The oxidation tube 13 is connected to the outlet of the sample introduction opening / closing valve 12. The oxidation tube 13 has a combustion part 13a on the upstream side and an oxidation part 13b filled with an oxidizing agent (oxidation catalyst) on the downstream side. The oxidation tube 13 burns the sample M supplied from the autosampler 11 to the combustion unit 13a to generate a sample gas, and further contacts the oxidant filled in the oxidation unit 13b with the sample gas in the sample gas. Carbon dioxide and nitrogen monoxide are oxidized to carbon dioxide and nitrogen oxides. The oxidizing agent is, for example, granular chromium oxide (Cr203) having a particle diameter of 1 to 2 mm filled on the upstream side, and granular silver cobalt oxide (Co3O4 / Ag) having a particle diameter of 1 to 2 mm filled on the downstream side. ) And two types of reagents. The reduction tube 14 is connected to the oxidation tube 13 so as to form a U shape, and reduces nitrogen oxide in the sample gas to nitrogen gas. The reaction gas supply means 15 supplies a reaction gas that burns the sample M in the oxidation tube 13. The carrier gas supply means 16 supplies a carrier gas for transporting the sample gas to the reduction means 14.
[Operation of pretreatment equipment for elemental analysis]
The sample introduction opening / closing valve 12 is opened, the sample M in the autosampler 11 is supplied to the combustion section 13a of the oxidation tube 13, and the switching gas 17 supplies the reaction gas supplied from the reaction gas supply means 15 to the combustion section 13a. Supply. Thereby, the sample M in the combustion part 13a is burned with the reaction gas to obtain a sample gas. Next, the switching valve 17 is switched. Thereby, carrier gas is supplied to the combustion part 13a through this switching valve 17. FIG. With this carrier gas, the sample gas is fed to the oxidation part of the oxidation tube, and the sample gas is oxidized with an oxidizing agent. Subsequently, the sample gas is fed to the reducing section 14a of the reducing tube 14 with the carrier gas, where the nitrogen oxide in the sample gas is brought into contact with the reducing agent and reduced to nitrogen gas. For this reason, the measurement gas of the mixed state of nitrogen gas and carbon dioxide gas for isolate | separating into nitrogen gas and carbon dioxide gas in a gas chromatograph is produced | generated.
[Detailed description of characteristic components]
As shown in FIG. 2, the switching valve 17 of the present embodiment includes a valve housing 171, a valve body 172 accommodated in the valve housing 171, and a pneumatic rotary actuator 173 that reciprocally rotates the valve body 172 by 90 degrees (see FIG. 2). 1), and a rotary four-way valve. The pneumatic rotary actuator 173 is provided apart from the valve housing 171 and has an output shaft 175 connected to the shaft portion 174 of the valve body 172.

  The switching valve 17 is provided with a valve housing 171 inside the chamber 19. The chamber 19 has an inlet 19 a and an outlet 19 b for purge gas, and has a through hole for four pipes connected to the switching valve 17 and a through hole for the output shaft 175.

  The chamber 19 introduces an inert gas supplied from the purge gas supply means 22, specifically, helium gas or argon gas as a purge gas from the inlet 19 a and discharges it from the outlet 19 b and through holes of four pipes. For this reason, since the valve casing 171 is completely cut off from the air by the chamber 19, the switching valve 17 blocks the mixing of air into the reaction gas or the carrier gas that is alternatively supplied to the oxidation tube 13.

  The valve housing 171 of the switching valve 17 has a first input port a, a second input port b, a first output port c, and a second output port d.

The first input port a is connected to the reaction gas supply means 15 via the reaction gas supply pipe 20a. The second input port b is connected to the carrier gas supply means 16 via a carrier gas supply pipe 20b. The first output port c is connected to a purge gas inlet pipe 12c upstream of the sample introduction opening / closing valve 12 via a purge gas supply pipe 20c. The second output port d is connected to a reaction gas / carrier gas inlet pipe 12d downstream of the sample introduction opening / closing valve 12 via a reaction gas / carrier gas supply pipe 20d. The valve body 172 has a first communication port e and a second communication port f connected to one of the two input ports a and b and one of the two output ports c and d.
[Features]
The controller 21 shown in FIG. 1 controls the servo motor 11a that intermittently rotates the sample feed table of the autosampler 11 and the pneumatic rotary actuator 173 of the switching valve 17 so as to repeatedly operate in a predetermined time series. There is a power transmission system (not shown) on the output shaft of the servo motor 11a, and the intermittent rotation of the sample feed table of the autosampler 11 and the opening / closing operation of the sample introduction opening / closing valve 12 are interlocked via this power transmission system.

  As shown in FIGS. 2 and 4, the switching valve 17 reciprocally rotates the valve body 172 (see FIG. 2) 90 degrees by the pneumatic rotary actuator 173 (see FIG. 1), Is alternatively supplied to the oxidation tube 13. Regardless of the switching state of the switching valve 17, the supply of the reaction gas and the carrier gas is not stopped at the switching valve 17.

  The sample introduction opening / closing valve 12 accommodates the sample M supplied from the autosampler 11 in the U-shaped recess when the U-shaped recess provided in the valve body 12b is upward. From this state, as shown in FIGS. 1 and 2, when the valve body 12 b rotates 180 degrees and the U-shaped concave portion faces downward, the sample M falls into the oxidation tube 13 by its own weight. When the switching valve 17 is in the state shown in FIGS. 1 and 2, the first input port a and the second output port d communicate with each other via the first communication port e, and the second input port b And the first output port c communicate with each other via the second communication port f. Thereby, the switching valve 17 supplies the reaction gas (oxygen) to the oxidation tube 13 and supplies the carrier gas (helium gas) as the purge gas to the bottom of the autosampler 11.

  When the reaction gas is supplied to the oxidation tube 13, ignition is performed and the sample M burns. The switching valve 17 changes from the operation state shown in FIGS. 1 and 2 to the operation state shown in FIGS. At this time, the switching valve 17 communicates with the first input port a and the first output port c via the first communication port e, and with the second input port b and the second output port d. Is in an operating state in which communication is established via the second communication port f. Accordingly, the switching valve 17 supplies the carrier gas to the oxidation tube 13 and supplies the reaction gas as the purge gas to the bottom of the autosampler 11.

  In this case, in the switching valve 17, the valve casing 171 is surrounded by the chamber 19 and the inside of the chamber 19 is purged with helium gas or argon gas from the purge gas supply means 22. For this reason, there is no air mixed in from the opening of the valve casing 171 of the switching valve 17 through the shaft that drives the valve body 172.

1 and FIG. 2, that is, the time for supplying the reaction gas (oxygen) to the oxidation tube 13 and the time for the operation state for supplying the carrier gas (helium gas) as the purge gas to the bottom of the autosampler 11 are as follows. Just a few seconds. The remaining time in the measurement cycle time is the operating state shown in FIGS. 3 and 4, that is, the carrier gas (helium gas) is supplied to the oxidation tube 13 and the reaction gas (oxygen) is supplied to the bottom of the autosampler 11. It is the time of the operation state supplied as purge gas. Therefore, since the inside of the autosampler 11 is purged with oxygen heavier than air, the initial residence air between the bottom of the autosampler 11 and the upper end of the sample introduction opening / closing valve 12 is effectively discharged. Even if the carrier gas (helium gas) enters the autosampler 11 as a purge gas, it moves to the inner surface of the lid in the autosampler 11, and the lower half of the autosampler 11 is occupied by oxygen heavier than air. For this reason, oxygen occupies the valve body 12b of the sample introduction opening / closing valve 12. Therefore, when the sample introduction opening / closing valve 12 supplies the sample M to the oxidation tube 13, no air is mixed therein.
〔Time chart〕
FIG. 5 is a time chart of the control output signal of the controller 21.

The controller 21 outputs the first signal S1 and the second signal S2 shown in FIG. The first signal S <b> 1 is a signal for driving the pneumatic rotary actuator 173 of the switching valve 17. The second signal S2 is a signal for driving the servo motor 11a via a motor driver (not shown).
[First signal S1]
The controller 21 maintains the output level of the first signal S1 at “0” until the waiting time t1 elapses after the pretreatment for elemental analysis is started, and during this time, the carrier gas (He) is oxidized. This is supplied to the tube 13, and when the waiting time t1 has elapsed, the output level of the first signal S1 is set to "1", and this state is held for the time t2. The pneumatic rotary actuator 173 rotates the valve body 172 of the switching valve 17 by 90 degrees from the state shown in FIG. 4 when the output level of the first signal S1 changes from “0” to “1”. This state is maintained for the time t2, and during this time, the reaction gas (O ₂ ) is supplied to the oxidation tube 13. Further, when the output level of the first signal S1 is changed from “1” to “0”, the pneumatic rotary actuator 173 rotates the valve body 172 by 90 degrees from the state of FIG. 2 to the state of FIG. The carrier gas (He) is supplied to the oxidation tube 13 again.
[Second signal S2]
Further, the controller 21 maintains the output level of the second signal S2 at “0” from the start of the preprocessing for elemental analysis until the waiting time t3 elapses, and the first time when the waiting time t3 elapses. The output level of the second signal S2 is set to “1”, and this state is held for the time t4.

  The elapsed time of t3 corresponds to an approximately intermediate time of the holding time t2 of the output level “1” of the first signal S1. The elapsed time t4 is necessary after the sample dropped into the oxidation tube 13 is burned with the reaction gas and the output level of the first signal S1 is changed from “1” to “0” and the supply of the carrier gas is started. This is the point in time.

When the output level of the second signal S2 changes from “0” to “1”, the servo motor 11a rotates the valve body 12b of the sample introduction opening / closing valve 12 by 180 ° to form the valve body 12b. The concave portion is positioned so as to be downward from the upward position, and the sample M accommodated in the concave portion is dropped into the oxidation tube 13. The servo motor 11a rotates the rotation frame in the autosampler 11 by one frame, and the sample stored in one frame of the rotation frame passes through the inlet of the sample introduction opening / closing valve 12 and onto the valve body 12b. Drop it. Further, when the output level of the second signal S2 changes from “1” to “0”, the servomotor 11a further rotates the valve body 12b by 180 ° and causes the sample dropped onto the valve body 12b to face upward. It is received in the recessed part.
[Brief description of other components]
Although an oxygen cylinder is used as the reaction gas supply means, any means capable of supplying an optimum amount of pure oxygen (reaction gas) for burning the sample necessary for burning the sample may be used. As the carrier gas supply means, a helium gas cylinder is used, but an inert gas such as argon (Ar) may be used. The oxidation tube 13 is formed of a transparent cylindrical tube of quartz having a small step on the downstream side. The reduction pipe 14 is made of, for example, a quartz transparent pipe, and includes a reduction section that is filled with a reducing agent and is formed on the upstream side, and an exhaust section that is formed on the downstream side.

The gas chromatograph 3 is a device that completely separates the sample gas (mixed gas) introduced through the moisture trap into the measurement gas components (CO ₂ ) and (N ₂ ) as analysis components.

The open split 4 includes the measurement gas sent from the gas chromatograph 3, helium gas (He) as a carrier gas, standard nitrogen gas (N ₂ ) and standard carbon dioxide gas (CO ₂ ) as inspection standards. It is an apparatus that alternately supplies the analysis means 5.

The analysis means 5 measures the stable isotope ratio and mass of the element component of the measurement gas obtained by the gas chromatograph 3, converts the analysis result of the element component in the sample M into an electric signal, and monitors it (not shown). ). In the measurement of the stable isotope ratio of carbon ( ¹² C, ¹³ C) and nitrogen ( ¹⁴ N, ¹⁵ N) by this analysis means 5, the carbon / nitrogen stability of the gases to be measured (CO ₂ ), (N ₂ ) The measurement of the isotope ratio and the measurement of the carbon / nitrogen stable isotope ratio with each of the standard gases (CO ₂ ) and (N ₂ ) with known stable isotope ratios are alternately performed and compared, The average value of the deviation is calculated.

[Other Embodiments]
The present invention is not limited to the above-described embodiments and examples, and the technical scope of the claims includes various design changes within the scope of the invention.

  (1) Although the pneumatic rotary actuator is used as the switching valve 17 in the above embodiment, an electrically driven or electromagnetically driven actuator such as a solenoid motor may be used.

  (2) Although the autosampler has been exemplified in the above embodiment, the sample holding member of the present invention is not limited to the autosampler.

  A practical apparatus A related to an elemental analysis apparatus including the pretreatment apparatus for elemental analysis of Patent Document 1 used by the present inventors and a pretreatment apparatus for elemental analysis according to the present invention remodeled based on this practical apparatus. FIG. 7 shows the results of elemental analysis using the practical apparatus B of the elemental analysis apparatus including the elemental analysis apparatus.

In FIG. 7, the horizontal axis represents the mass (unit: microgram) of nitrogen ( ¹⁵ N), and the vertical axis represents δ ¹⁵ N (actual measured value) −δ ¹⁵ N (true value) of nitrogen ( ¹⁵ N). It is a distribution graph showing the measurement results. In FIG. 7, the mark ◇ indicates the measurement result of the test apparatus A according to the present invention of Patent Document 1, and the mark ♦ indicates the measurement result of the practical apparatus B according to the present invention.

  As shown in FIG. 7, the marks marked with ◇ are gathered around a deviation value of 0 when the mass of nitrogen and the mass of carbon in the sample are each 100 μg or more. In FIG. 7, when the mass of nitrogen in the sample is less than 100 μg, the deviation becomes large and greatly varies, and measurement accuracy does not appear. Therefore, the practical apparatus A shows that the limit of accurate measurement with little variation in measurement accuracy is around 100 μg.

  On the other hand, in FIG. 7, when the mass of nitrogen of the sample is 8 μg to 0.1 μg, the marks of ◆ are gathered around the deviation value 0 and distributed.

M Sample 1 Element analyzer 2 Element analysis pretreatment device 3 Gas chromatograph 4 Open split 5 Analyzing means 11 Autosampler 12 Sample open / close valve 13 Oxidation tube 14 Reduction tube 15 Reaction gas supply means 16 Carrier gas supply means 17 Switching valve 171 Valve housing 172 Valve body 173 Pneumatic rotary actuator (actuator)
a first input port b second input port c first output port d second output port e first communication port f second communication port 18 moisture trap 19 chamber 22 purge gas supply means

Claims (4)

A sample holding member that contains a sample in a state purged with a purge gas and supplies the sample through a sample introduction opening / closing valve;
An oxidation tube connected to the sample introduction on-off valve, combusting the sample supplied from the sample holding member to generate a sample gas, and oxidizing the sample gas;
A reduction pipe connected to the oxidation pipe for reducing nitrogen oxide in the sample gas to nitrogen gas;
Reactive gas supply means for supplying a reactive gas for burning the sample;
Carrier gas supply means for supplying a carrier gas for transporting the sample gas to the reducing means;
A switching valve that alternatively supplies the reaction gas and the carrier gas to the oxidation tube;
A gas chromatograph for separating the generated gas;
In a pretreatment device for elemental analysis, comprising:
The switching valve is provided with a valve housing inside the chamber and an actuator for driving the valve body outside the chamber,
In the chamber, helium gas or argon gas, which is an inert gas different from the carrier gas, is introduced as a purge gas, and is supplied from the switching valve to the oxidation tube alternatively into the reaction gas or the carrier gas. A pretreatment device for elemental analysis, characterized in that it is configured to block air contamination. A sample holding member that contains a sample in a state purged with a purge gas and supplies the sample through a sample introduction opening / closing valve;
An oxidation tube connected to the sample introduction on-off valve, combusting the sample supplied from the sample holding member to generate a sample gas, and oxidizing the sample gas;
A reduction pipe connected to the oxidation pipe for reducing nitrogen oxide in the sample gas to nitrogen gas;
Reactive gas supply means for supplying a reactive gas for burning the sample;
Carrier gas supply means for supplying a carrier gas for transporting the sample gas to the reducing means;
A switching valve that alternatively supplies the reaction gas and the carrier gas to the oxidation tube;
A gas chromatograph for separating the generated gas;
In a pretreatment device for elemental analysis, comprising:
The switching valve is provided with a valve housing inside the chamber and an actuator for driving the valve body outside the chamber,
In the chamber, helium gas or argon gas, which is an inert gas different from the carrier gas, is introduced as a purge gas, and is supplied from the switching valve to the oxidation tube alternatively into the reaction gas or the carrier gas. Configured to block air entrainment,
Elemental analysis characterized in that the reaction gas or the carrier gas is introduced in a switching manner via the switching valve as a purge gas for the sample holding member upstream of the sample introduction opening / closing valve. Pre-treatment device. The switching valve includes a first input port for inputting the reaction gas, a second input port for inputting the carrier gas, and a first output port connected to an upstream position of the sample introduction opening / closing valve. A second output port connected to a downstream position of the sample introduction on-off valve,
When the sample introduction opening / closing valve is in a state where the sample is not supplied to the combustion section, the first input port and the first output port are communicated with each other and the second input port and the second input port are communicated with each other. Communicate with the output port,
When the sample introduction on-off valve is in a state where the sample is supplied to the oxidation tube, the first input port and the second output port are communicated with each other and the second input port and the first output are communicated. The element analysis pretreatment device according to claim 1, wherein the element analysis pretreatment device is configured to communicate with a port.   An elemental analysis apparatus comprising: the elemental analysis pretreatment apparatus according to any one of claims 1 to 3; and an analysis unit connected to the elemental analysis pretreatment apparatus.

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