JP2002005913A - Head space sample introduction device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent dilution of sample gas caused by inflow of carrier gas into a barrel of a syringe from the high-pressure sample vaporization chamber side, when injecting the sample gas into the sample vaporization chamber from the syringe. SOLUTION: A cock 26 is installed on a communication part between the barrel 23 and a needle 24, to roughly seal the inside of the barrel 23 by the cock 26. The sample gas is sucked from an upper space in a vial 16 by pulling a plunger 25, and then the cock 26 is closed, and the plunger 25 is thrust, to heighten the pressure of the sample gas up to roughly the same pressure as the gas pressure in the sample vaporization chamber 41. Thereafter, the needle 24 is allowed to penetrate a septum 42 on the upper part of the sample vaporization chamber 41, and the cock 26 is opened, and the plunger 25 is thrust, to inject the sample gas into the sample vaporization chamber 41.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a headspace sample introducing apparatus for collecting a sample gas volatilized from a liquid sample or a solid sample by a headspace method and introducing the sample gas into a gas chromatograph or the like.

[0002]

2. Description of the Related Art In a headspace analysis method, components having a relatively low boiling point are volatilized by heating a liquid sample or a solid sample contained in a container to a constant temperature for a certain period of time, and the components are removed from the upper space in the container. A certain amount of the contained gas is sampled and introduced into a gas chromatograph or the like for analysis. Chromatographic analysis using these methods
For example, it is suitable for measuring flavors in foods, measuring volatile organic compounds in water, and the like.

[0003] A syringe is most simply used to collect gas from the upper space in the container and introduce the gas into the gas chromatograph. In the syringe, a plunger is inserted into the other open end surface of a substantially cylindrical barrel having a needle on one closed end surface, and a sample gas is sucked into the barrel via a needle by reciprocation of the plunger. Or the sample gas stored in the barrel is discharged through a needle.

[0004]

When a sample gas is sucked from a container, the gas collected inside the barrel of the syringe is substantially at atmospheric pressure. On the other hand, the inside of the sample vaporization chamber of the gas chromatograph into which the sample gas is injected has a gas pressure considerably higher than the atmospheric pressure in order to send the carrier gas to the column. Therefore, when the needle of the syringe penetrates the septum provided above the sample vaporization chamber, the carrier gas flows into the barrel of the syringe via the needle, and the sample gas in the barrel is diluted. Even if the absolute amount of the analyte is the same, comparing the case of injecting a large amount of low-concentration sample gas with the case of injecting only a small amount of high-concentration sample gas shows that the former peaks on the chromatogram. Are spread in the time direction, and the peak top is lowered, and the detection sensitivity is lowered.

The present invention has been made in view of the above points, and an object of the present invention is to prevent dilution of a sample gas as described above and maintain high detection sensitivity in a gas chromatograph. It is an object of the present invention to provide a headspace sample introduction device capable of performing the above-described steps.

[0006]

Means for Solving the Problems and Embodiments of the Invention
The present invention has been made to solve the above problems, a barrel,
A headspace sample introduction device that includes a syringe including a needle and a plunger, and uses the syringe to collect a sample gas from an upper space in a sample container and inject the sample gas into a sample vaporization chamber of a gas chromatograph device. a) barrel sealing means for making the inside of the barrel substantially sealed; and b) between the sampling of the sample gas in the barrel and the injection into the sample vaporization chamber, the barrel inside is substantially sealed by the barrel sealing means. Pressurizing control means for pressing the plunger to a predetermined position in that state to pressurize the sample gas.

[0007] In a gas chromatograph, in order to feed a carrier gas at a substantially constant flow rate into a column connected to a sample vaporization chamber, the interior of the sample vaporization chamber is usually set to have a gas pressure higher than the atmospheric pressure. I have. In the headspace sample introduction device according to the present invention, at the time when the sample gas is sucked into the barrel of the syringe, the gas pressure of the sample gas in the barrel is substantially at the atmospheric pressure. The pressure of the sample gas is increased by pushing the plunger while the inside of the barrel is substantially sealed by the barrel sealing means. Then, a needle is inserted into the sample vaporization chamber while the sample gas is pressurized, and the sealing of the barrel is released.
If the gas pressure is increased to the same level as the gas pressure in the sample vaporization chamber when pressurizing the sample gas, there is almost no pressure difference between the inside of the barrel and the sample vaporization chamber even when the sealing of the barrel is released. Therefore, it is possible to prevent the carrier gas from flowing into the barrel from the sample vaporization chamber side.

When the sample gas is pressurized so long as the gas pressure is at least higher than the atmospheric pressure, the pressure difference between the sample gas and the sample vaporization chamber is reduced. When the sealing of the barrel is released, gas inflow from the sample vaporization chamber side can be reduced.

One embodiment of the barrel sealing means may be a flow passage opening / closing mechanism for opening / closing an internal flow passage communicating between the barrel and the needle. In this configuration,
After the sample gas is sucked into the barrel with the flow path opened by the flow path opening / closing mechanism, the flow path is closed, and in this state, the plunger is pushed in to pressurize the sample gas. Then, the needle is passed through the septum in the upper part of the sample vaporization chamber as it is, and the flow path is opened to inject the sample gas.

In another embodiment of the barrel sealing means, an opening / closing member that closes or opens a hole provided in the needle from the outside according to the vertical movement of the syringe can be provided. Specifically, the opening / closing member can use a needle guide for protecting the needle, and it is preferable that the opening / closing member be made of an elastic body in order to reliably close the hole. In this configuration, after the sample gas is sucked into the barrel, the needle hole is closed by the opening / closing member, and in this state, the plunger is pushed in to pressurize the sample gas. Then, the syringe is lowered so that the lower surface of the opening / closing member is in close contact with the upper surface of the septum above the sample vaporization chamber, and the syringe is further lowered to expose the needle hole into the sample vaporization chamber.

[0011]

According to the headspace sample introducing apparatus according to the present invention, when a sample gas is injected into a sample vaporizing chamber of a gas chromatograph, there is no difference in gas pressure between the sample vaporizing chamber and the barrel. Since it is small, it is possible to prevent the carrier gas from flowing into the barrel from the sample vaporization chamber. Therefore, the sample gas is not diluted in the barrel before the sample is injected, and the sample gas can be sent to the column in a short time, so that a sharp peak can be obtained on the chromatogram. Thereby, the minimum detectable amount of the target component can be reduced, and the detection sensitivity is improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a headspace sample introducing apparatus according to the present invention (hereinafter referred to as "embodiment 1") will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of the headspace sample introduction device of the present embodiment. This headspace sample introduction device is a device for introducing a sample into a gas chromatograph device, and FIG. 1 also shows a sample vaporization chamber and a column which are a part of the gas chromatograph device.

First, the configuration of this device will be described with reference to FIG. The sample exchange unit 10 includes a turntable 11 on which a plurality of vials 16 storing samples are placed, and a motor 12 that rotates the turntable 11 (in the direction of arrow E in the figure).
And an air cylinder 13 which is provided below the turntable 11 and has an arm which extends and contracts substantially vertically upward (in the direction of arrow D in the figure). Above the air cylinder 13, a vial heat retaining block 15 for housing and heating the vial 16 therein is disposed. Above the vial heat retaining block 15, a gas chromatograph 40
The injector unit 20 is provided so as to be movable between and above the sample vaporization chamber 41. The injector unit 20 includes a syringe heat retaining block 21 for accommodating a syringe 22 therein. The injector horizontal drive unit 30 moves in the horizontal direction (the direction of arrow A in the figure), and the syringe vertical drive unit 31 moves in the vertical direction (arrow B in the figure). Direction).

The syringe 22 has a substantially cylindrical barrel 23.
And a needle 24 attached to the tip of the barrel 23
And a plunger 25 fitted into the barrel 23, and the plunger 25 is pushed or pulled into the barrel 23 by the plunger drive unit 32 (in the direction of arrow C in the figure). As one of the features of this embodiment,
The syringe 22 has a cock 26.

FIG. 2 is a partial sectional view of the syringe 22 showing the structure of the cock 26. Cock 26 is barrel 23
261 attached between needle and needle 24
And a tubular flow path 26 inside and inside the connecting body 261
And a rotating body 262 having a substantially columnar shape having a rotating member 4. The rotating body 262 rotates in conjunction with the rotation of the lever 263. That is, as shown in FIG. 2B, when the lever 263 is positioned substantially perpendicular to the extension direction of the syringe 22, the flow path 26
4 connects the inside of the barrel 23 with the needle 24. When the lever 263 is rotated as shown in FIG. 2A, the inside of the barrel 23 and the needle 24 are shut off, and the inside of the barrel 23 is substantially closed.

Returning to FIG. 1, the lever 263 is rotatably driven by the cock driving unit 33. Syringe horizontal drive unit 30, syringe vertical drive unit 3
1. The operations of the plunger drive unit 32, the cock drive unit 33, the motor 12, the air cylinder 13, and the like are totally controlled by a control unit 34 including a CPU. The operation unit 35 is used for setting various conditions.
Syringe temperature, vial temperature, vial warming time, analysis cycle, sampled amount, etc. can be set.

Next, a series of operations in the above configuration from collecting the sample gas volatilized from the sample solution to injecting the sample gas into the sample vaporizing chamber 41 of the gas chromatograph device 40 will be described with reference to the flowchart of FIG.

The operator puts the sample liquid into the vial 16, seals it with a rubber septum 17, and turns the turntable 1.
1 (step S1). When the operator sets an appropriate condition using the operation unit 35 and instructs the start of the operation, or when instructed to start the analysis according to a predetermined time schedule, the motor 12 is controlled by the motor under the control of the control unit. The turntable 11 is rotated. Then, the desired vial 16 is placed in the heat retaining block 1.
When the pressure reaches just below 5, the vial 16 is pushed up by the air cylinder 13 and accommodated in the heat retaining block 15 (step S2). The heat retaining block 15 is maintained at a predetermined temperature by a heater (not shown), and the vial 16 is maintained here for a predetermined time, during which time the volatilization of components from the sample liquid is promoted (step S3). On the other hand, the syringe 22 is also maintained at a predetermined temperature by the syringe heat retaining block 21.

After the vial 16 is held in the heat retaining block 15 for a predetermined time, the syringe 22 is operated as follows.
Sample gas is collected. At this time, the syringe 22
The plunger 25 is located at the position where it is most pushed into the barrel 23, and the cock 26 is open. The injector unit 20 is moved by the syringe vertical drive unit 31 to a position where the needle 24 penetrates the septum 17 of the vial 16 (strictly speaking, the hole of the needle 24 is
(Step S4). Next, the plunger 25 is pulled out by the plunger drive unit 32, whereby the sample gas in the upper space in the vial 16 is collected in the barrel 23 (Step S5). At this time, the withdrawal amount of the plunger 25 depends on the amount of the sample gas collected. The gas pressure of the sample gas in the barrel 23 immediately after the sampling is approximately atmospheric pressure.

Thereafter, the cock 26 is closed by the cock driving unit 33 (step S6). As a result, the inside of the barrel 23 is stored in a substantially sealed state in which the sample gas is stored. The injector unit 20 is raised by the syringe vertical drive unit 31 (step S7), and is further moved to a position immediately above the sample vaporization chamber 41 (the position indicated by the two-dot chain line in FIG. 1) by the syringe horizontal drive unit 30 (step S8). . Subsequently, the plunger 25 is driven by the plunger driving unit 32.
Is pushed to a predetermined position (step S9). As described above, since the barrel 23 is in a substantially sealed state, there is no inflow of air from the outside, and the gas pressure is increased by the reduced volume of the sample gas. The gas pressure of the sample gas after pressurization is determined by the amount of plunger 25 pushed in at this time. For example, the pushing amount may be determined based on the set gas pressure in the sample vaporization chamber 41 so that the gas pressure of the sample gas is equal to or slightly lower than the set gas pressure. The operator may be allowed to set the gas pressure of the sample gas from the operation unit 35. In any case, it is preferable that the upper limit of the gas pressure of the sample gas is limited in consideration of the pressure resistance of the barrel 23.

Next, while the plunger 25 is being pushed in, the injector unit 20 is driven by the syringe vertical drive unit 31.
Is lowered until the needle 24 passes through the septum 42 above the sample vaporizing chamber 41 and the needle hole is exposed in the internal space of the sample vaporizing chamber 41 (step S10). Thereafter, the cock 26 is opened by the cock driving unit 33 (step S11). At this time, since the gas pressures in the sample vaporization chamber 41 and the barrel 23 are almost the same, there is almost no gas movement between the two. If the gas pressure in the barrel 23 is higher than the gas pressure in the sample vaporization chamber 41, the sample gas leaks into the sample vaporization chamber 41 before injecting the sample. Therefore, it is safer to set the gas pressure in the barrel 23 when the sample gas is pressurized to be slightly lower than the gas pressure in the sample vaporization chamber 41.

After the cock 26 is opened as described above, the plunger 25 is pushed into the barrel 23 by the plunger driving unit 32 at a predetermined timing (step S12). As a result, the sample gas sucked into the barrel 23 is instantaneously injected into the sample vaporization chamber 41. The carrier gas flows into the column 43 in the sample vaporization chamber 41. Since the sample gas is not diluted by the carrier gas, it is sent into the column 43 in a short time. Therefore, even after being separated into each component while passing through the column 43, the same component does not spread much in the time axis direction and appears as a sharp and high peak when creating a chromatogram.

In the above series of operations, the processing relating to some of the steps can be performed in a different order or at the same time. In short, after the sample gas is sucked into the barrel 23, the needle 24 is inserted into the sample vaporization chamber 41.
At any time before the holes are exposed, the cock 26 is closed, the plunger 25 is pushed to a predetermined position to pressurize the sample gas, and while the cock 26 is closed,
That is, the needle 24 may be passed through the septum 42 while maintaining the gas pressure of the sample gas.

Next, another embodiment according to the present invention (hereinafter referred to as "embodiment 2") will be described. The overall configuration of the headspace sample introduction device of the second embodiment is the same as that of the first embodiment.
The description is omitted here. The feature of the second embodiment is that the second embodiment has a configuration different from that of the first embodiment in order to seal the inside of the barrel 23 to increase the pressure of the sample gas.

FIG. 3 is a diagram showing the configuration and operation of the main part of the injector unit according to the second embodiment. Conventionally, in this type of device, a needle guide is provided along with a syringe. The needle guide is provided for the purpose of protecting the needle, more specifically, for preventing the needle from being bent due to resistance received from the septum when penetrating the septum, and is generally made of metal. In this embodiment, the needle guide 27 is connected to the septum 17, 42.
It is formed of the same elastic material such as rubber. The holder 28 holding the needle guide 27 is fitted with a vertical movement mechanism of the syringe 22 by a predetermined lock mechanism, and basically moves up and down in conjunction with the vertical movement of the injector unit 20, but descends. In this case, when the position is restricted downward, the lock is released and only the syringe 22 can be lowered.

Other than during sample suction and sample injection, the positional relationship between the syringe 22 and the needle guide 27 is shown in FIG.
In the state shown in FIG. That is, the needle 24 is partially penetrated through the needle guide 27, and at this time, the hole 241 opened on the side surface of the needle 24 is inside the needle guide 27 and is closed. Needle guide 2
Since 7 is made of rubber, it has good adhesion, and the inside of the barrel 23 is almost completely sealed. In other words, in the first embodiment, the cock 26 is in a closed state, and in this state, the sample gas in the barrel 23 can be pressurized by pushing the plunger 25 to a predetermined position in the barrel 23.

FIGS. 3B and 3C show the states when the sample gas is injected and when the sample gas is sucked, respectively. At the time of suction and injection of the sample gas, the injector unit 20 is lowered to a predetermined position.
The lower surface of the needle guide 27 which descends in conjunction with 2 abuts on the upper surfaces of the septa 17 and 42. Then, syringe 2
The lock of the needle guide 27 with respect to 2 is released,
The needle guide 27 stops at that position and the syringe 22
Only falls further. That is, the needle guide 27 stops at the upper part of the septum 17, 42, and only the needle 24 slides in the through hole of the needle guide 27, and the vial 16
Or, it is inserted into the sample vaporization chamber 41, and the hole 241 is exposed to the internal space. This is cock 2 in the first embodiment.
In a state in which the plunger 25 is opened, the sample gas is sucked into the barrel 23 or the sample gas is injected from the barrel 23 in accordance with the pulling or pushing of the plunger 25. Since the needle guide 27 is made of rubber, the needle guide 27 has good adhesion to the septum 17, 42, and a gap through which the sample gas flows is hard to be formed on the adhesion surface. Therefore, it is possible to prevent the sample gas from leaking from the gap.

It should be noted that the above embodiment is merely an example, and it is apparent that modifications and modifications can be made as appropriate in the spirit of the present invention.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part of a first embodiment of a headspace sample introduction device according to the present invention.

FIG. 2 is a partial cross-sectional view of a syringe showing a structure of the cock according to the first embodiment.

FIG. 3 is a diagram illustrating a configuration and operation of a main part of an injector unit according to a second embodiment.

FIG. 4 is a flowchart illustrating an operation from sampling gas injection to injection according to the first embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 16 ... Vial 17 ... Septum 20 ... Injector unit 21 ... Syringe heat retaining block 22 ... Syringe 23 ... Barrel 24 ... Needle 241 ... Hole 25 ... Plunger 26 ... Cock 261 ... Connected body 262 ... Rotating body 263 ... Lever 264 ... Flow path 27 ... Needle guide 28 Holder 30 Syringe horizontal drive unit 31 Syringe vertical drive unit 32 Plunger drive unit 33 Cock drive unit 34 Control unit 35 Operation unit 40 Gas chromatograph device 41 Sample vaporization chamber 42 Septum 43 column

Claims (3)

[Claims] A syringe including a barrel, a needle and a plunger is provided. A sample gas is collected from an upper space in a sample container using the syringe, and the sample gas is injected into a sample vaporization chamber of a gas chromatograph device. In the headspace sample introduction device, a) barrel sealing means for making the inside of the barrel substantially sealed; and b) said barrel sealing means between the time when the sample gas is collected in the barrel and the time when it is injected into the sample vaporization chamber. And a pressurizing control means for pressurizing the sample gas by pushing the plunger to a predetermined position in this state. 2. The headspace sample introduction device according to claim 1, wherein the barrel sealing means is a flow passage opening / closing mechanism that opens and closes an internal flow passage communicating between the barrel and the needle. 3. The headspace sample introduction according to claim 1, wherein the barrel sealing means is an opening / closing member that closes or opens a hole provided in the needle from outside according to the vertical movement of the syringe. apparatus.