Sample introduction method and sample introduction device

Abstract

A sample introduction method according to an aspect of the present invention is a sample introduction method for collecting and injecting a sample by an SPME method using an SPME Arrow, and comprises: an adsorption step (S3) for adsorbing a target component in a sample to an adsorption unit of an SPME Arrow; an exposure step (S4) for exposing the adsorption unit of the SPME Arrow after the adsorption step to a dry inert gas atmosphere for a predetermined time; and an injection step (S5) for heating the adsorption unit of the SPME Arrow after the exposure step to separate the target component from the adsorption unit and introducing the target component into an analysis device.　

Description

Sample introduction method and sample introduction device

[0001] The present invention relates to a sample introduction method and device for introducing a sample into an analytical device such as a gas chromatograph, and more particularly to a sample introduction method and device using solid-phase microextraction.

[0002] When analyzing low-concentration components in a sample using a gas chromatograph (hereinafter referred to as a "GC"), including a gas chromatograph mass spectrometer, the target components must be concentrated before being introduced into the GC. Solid phase microextraction (SPME) is one of the sample introduction methods widely used for this purpose.

[0003] In a typical SPME method, a thin, elongated fiber made of fused silica is first inserted into a container containing a sample (liquid or solid), and the target component in the gas phase volatilized from the sample is adsorbed onto an adsorbent (liquid phase) coated on the surface of the fiber. The fiber is then inserted into the vaporization chamber of a GC device and heated, causing the target component to desorb from the adsorbent and then be introduced into a column on the carrier gas for analysis (see Patent Document 1). However, with such conventional SPME fibers, it is difficult to increase the amount of components adsorbable to the adsorbent, posing a problem in terms of detection sensitivity. Another problem is the low mechanical durability of the fiber itself.

[0004] In response to this, a device called the SPME Arrow has been developed in recent years (see Non-Patent Document 1). The SPME Arrow uses a stainless steel rod with a larger outer diameter than conventional fibers, and a large amount of adsorbent is held on the surface of the rod. As a result, in the SPME method using the SPME Arrow, the amount of adsorption of the target component can be increased and the component can be concentrated to a high concentration compared to when conventional SPME fibers are used, enabling highly sensitive analysis.

[0005] Japanese Patent Application Laid-Open No. 2007-47156

[0006] Kawamura, "Analysis of Aroma Compound Profiles Using SPME Arrow-GC-MS Analysis," Journal of the Japan Society for Odor and Fragrance Environment, Vol. 52, No. 4, 2021

[0007] As disclosed in Non-Patent Document 1 and the like, the present inventors have been studying the use of SPME Arrow for GC analysis of odor components and the like in samples. Accurate odor analysis often requires highly quantitative detection of components present in very small amounts in a sample, and the SPME Arrow, which is capable of concentrating components to high concentrations, is a very useful device. However, through repeated experiments, it was found that, depending on the type of sample, the type of component, the GC analysis conditions, and the like, problems arise, such as the shape of the chromatographic peak being distorted, reducing the accuracy of quantification, or the retention time of the chromatographic peak being shifted, making accurate identification impossible.

[0008] The present invention has been made to solve these problems, and its main object is to provide a sample introduction method and device that can improve the quantitative performance and identification performance of target components in analysis that utilizes sample introduction by the SPME method using the SPME Arrow.

[0009] One aspect of the sample introduction method according to the present invention is a sample introduction method for collecting and injecting a sample by solid-phase microextraction using an SPME Arrow, comprising: an adsorption step of adsorbing a target component in the sample to the adsorption portion of the SPME Arrow; an exposure step of exposing the adsorption portion of the SPME Arrow after the adsorption step to a dry inert gas atmosphere for a predetermined time; and an injection step of heating the adsorption portion of the SPME Arrow after the exposure step to desorb the target component from the adsorption portion and introduce the target component into an analytical device.

[0010] One aspect of the sample introduction device according to the present invention is a sample introduction device that uses an SPME Arrow to collect a sample by solid-phase microextraction and inject it into an analytical device, and includes: an adsorption treatment section that inserts the adsorption section of the SPME Arrow into a container in which the sample is sealed and adsorbs a target component in the sample onto the adsorption section; an exposure treatment section that exposes the adsorption section of the SPME Arrow to a dry inert gas atmosphere for a predetermined period of time after component adsorption in the adsorption treatment section is completed; and a movement section that moves the SPME Arrow between the adsorption treatment section and the exposure treatment section, and between the exposure treatment section and a component introduction position where the target component adsorbed on the adsorption section is introduced into the analytical device.

[0011] The present inventors have repeatedly analyzed various samples and components under various analytical conditions, and have found that the main cause of the aforementioned chromatographic peak shape distortion and retention time shift is that a large amount of the solvent (aqueous solvent or organic solvent) contained in the sample is adsorbed to the adsorption section of the SPME Arrow and introduced into the analytical instrument (GC instrument). In contrast, the above-described sample introduction method and instrument according to the present invention can remove at least a portion of the solvent adsorbed simultaneously when the target component in the sample is adsorbed to the adsorption section of the SPME Arrow from the adsorption section before the analysis is performed.

[0012] As a result, the above-described sample introduction method and device according to the present invention can reduce the influence of solvents such as water and organic solvents derived from the sample during GC analysis, thereby suppressing distortion of the chromatographic peak shape of the target component and shifts in retention time, thereby improving the quantitative performance and identification performance of the target component.

[0013] 1 is a flowchart showing an example of the operation and processing procedure of the SPME method according to one embodiment of the present invention. 2 is a schematic diagram of an example of a sample introduction device for carrying out the SPME method according to this embodiment. 3 is a schematic diagram of the conditioning / solvent purging unit in FIG. 2. 4 is a diagram showing an example of a chromatogram obtained by GC analysis using a conventional SPME method.

[0014] [Causes of Problems Occurring in Conventional SPME Methods] As described above, the SPME Arrow holds a large amount of adsorbent (liquid phase) on the surface of the rod. Therefore, in the SPME method using the SPME Arrow, not only the target component contained in the sample but also a large amount of the solvent contained in the sample is adsorbed by the adsorbent. When the adsorption section of the SPME Arrow is heated in the vaporization chamber of the GC device, a large amount of the solvent is introduced into the column along with the high concentration of the target component. For example, when components in an aqueous sample are collected using the SPME Arrow, a large amount of water contained as a solvent in the sample is also collected by the adsorbent.

[0015] Figure 4 shows an example of a total ion chromatogram (TIC) obtained by GC / MS analysis of an aqueous sample using the conventional SPME method, along with an extracted ion chromatogram of m / z 18 for reference.

[0016] In mass spectra, the water-derived peak appears primarily at m / z 18. In typical GC / MS analysis, the lower limit of m / z (mass-to-charge ratio) is often set to around 35, so no water-derived peak is observed on the chromatogram. However, when the analysis is performed with the lower limit of m / z set to 17, a large water-derived peak is observed on the chromatogram (total ion chromatogram: TIC), as shown in Figure 4. The time range over which this water-derived peak is observed is wide, and peaks of components with retention times within this time range are placed on top of the water-derived peak curve, unavoidably distorting the peak waveform. Furthermore, peaks of other components that appear immediately after the large water-derived peak tend to have shifted retention times due to the large amount of water retained on the column.

[0017] The influence of solvents adsorbed in large amounts to the adsorbent of the SPME Arrow in GC analysis has not been generally known, and no measures have been taken to reduce this influence. In response to this, the present inventors have conceived of a method for reducing the influence of solvents by performing a step of removing the solvent without affecting the components adsorbed to the adsorbent as much as possible between the time when components are collected by the SPME Arrow and the time when the components are introduced into a GC system, and have thus completed the present invention. An SPME method, which is one embodiment of the sample introduction method according to the present invention, and an apparatus for carrying out the method will now be described with reference to the accompanying drawings.

[0018] [Configuration of an apparatus for carrying out the SPME method according to the present invention]

[0019] Fig. 1 is a flow chart showing an example of the operation and processing procedure in the SPME method of this embodiment. Fig. 2 is a schematic diagram of an example of a sample introduction device for carrying out this SPME method. Fig. 3 is a schematic diagram of the conditioning / solvent purging unit in Fig. 2.

[0020] The sample introduction device shown in Figure 2 corresponds to a device, such as the Shimadzu Corporation autosampler system "AOC-6000 Plus," that selectively collects multiple pre-prepared samples and automatically injects them into a GC system. This sample introduction device includes an SPME arrow 1, an SPME arrow drive unit 2, a conditioning / solvent purge unit 3, and a sample collection unit 4. The GC system 5 in Figure 2 includes a vaporization chamber 50, a column 51, and a detection unit 52. This GC system 5 itself is not included in the sample introduction device, but the vaporization chamber 50, together with the sample introduction device, functions to introduce the target component into the column 51.

[0021] SPME Arrow 1 is a commercially available product, such as that described in Non-Patent Document 1, and includes a holder 10, a plunger 11, a cylindrical needle 12, a rod 13 with an arrowhead-shaped tip, and an adsorption portion 14 formed on a portion of the surface of the rod 13. Fig. 2 is a diagram showing the rod 13 protruding from the needle 12, and the rod 13 can be retracted into the needle 12 by the plunger 11. The size of SPME Arrow 1 and the type of adsorbent (liquid phase) held in the adsorption portion 14 can be appropriately determined depending on the type of sample to be analyzed.

[0022] The SPME Arrow driving unit 2 includes a main body moving unit 20 and a plunger driving unit 21. The main body moving unit 20 moves the SPME Arrow 1 between the conditioning / solvent purging unit 3, the sample collection unit 4, and the vaporization chamber 50. The plunger driving unit 21 pushes or pulls the plunger 11 of the SPME Arrow 1 to advance or retract the rod 13 from or into the needle 12.

[0023] 3, the conditioning / solvent purging unit 3 includes a housing 30 having a recess 33 formed therein with a space sufficient to accommodate the rod 13 of the SPME Arrow 1, and a heating / cooling unit 34 for heating and cooling the housing 30. A gas supply opening 31 and a gas exhaust opening 32 are formed in the housing 30, and although not shown, a dry inert gas (He, N, etc.) is supplied to the recess 33 through a pipe connected to the gas supply opening 31, and the inert gas that has circulated inside the recess 33 is exhausted to the outside through a pipe connected to the gas exhaust opening 32.

[0024] [Operation and processing procedure of an example of the SPME method according to the present invention] The procedure from sample collection to analysis will be described with reference to Fig. 1. Note that the following description is based on the premise that the operations are performed automatically using the sample introduction device shown in Fig. 2, but it goes without saying that some of the operations can be performed manually by an operator.

[0025] Prior to the analysis, the operator prepares an SPME arrow of the type (size and adsorbent) appropriate for the analysis and attaches it to a predetermined position in the sample introduction device (Step S1). Note that if an SPME arrow used in a previous analysis is to be used subsequently, Step S1 is omitted.

[0026] Next, when an instruction to start analysis is given via an operation unit (not shown), the conditioning / solvent purge unit 3 conditions the SPME Arrow 1 (step S2). Specifically, the main body moving unit 20 moves the SPME Arrow 1 into the recess 33 of the conditioning / solvent purge unit 3, and the plunger driving unit 21 pushes the plunger 11 to expose the rod 13 (the adsorption unit 14). The heating / cooling unit 34 heats the adsorption unit 14 to a predetermined temperature (e.g., 200°C or higher) via the housing 30 and maintains that temperature for a certain period of time. As a result, the heated adsorption unit 14 is exposed to a dry inert gas atmosphere, and the various components adsorbed to the adsorption unit 14 are volatilized and removed. In other words, the adsorption unit 14 is purified. The components removed at this time are mainly components that were adsorbed to the adsorption section 14 during the previous analysis and were not desorbed by thermal desorption, and impurity components that adhered to the adsorption section 14 during storage of SPME Arrow 1.

[0027] After conditioning is complete, the sample is collected in the sample collection unit 4 (step S3). Specifically, the rod 13 of the SPME Arrow 1 is temporarily housed in the needle 12, and the main body movement unit 20 moves the SPME Arrow 1 to a predetermined position in the sample collection unit 4. The plunger drive unit 21 then pushes the plunger 11, inserting the tip of the rod 13 (the adsorption unit 14) into the headspace of one of the prepared vials. This vial contains a liquid or solid sample. The vial is heated to a moderate temperature (e.g., 60°C) and stirred at a predetermined rotation speed for a predetermined time. This promotes the volatilization of components from the sample, filling the headspace of the vial with the target component in a gaseous state. This target component in a gaseous state is adsorbed by the adsorption unit 14.

[0028] In step S3, since not only the target component but also a large amount of the solvent in the sample (in the case of a liquid sample) is present in the head space within the vial, this solvent is also adsorbed by the adsorption section 14. Therefore, in order to remove this solvent, a process is performed in which the adsorption section 14 of the SPME Arrow 1 is exposed for a predetermined time to an atmosphere in which a dry inert gas flows (step S4).

[0029] Specifically, the rod 13 of the SPME Arrow 1 is temporarily housed within the needle 12, and the main body moving unit 20 moves the SPME Arrow 1 into the recess 33 of the conditioning / solvent purging unit 3. The plunger driving unit 21 pushes in the plunger 11 to expose the rod 13 (adsorption unit 14). The heating / cooling unit 34 maintains the adsorption unit 14, via the housing 30, at an appropriate temperature (e.g., approximately 30 to 40°C) that will not volatilize the target component for a certain period of time. Because the adsorption unit 14 is exposed to an atmosphere of dry inert gas, the water and organic solvent adsorbed to the adsorption unit 14 are volatilized and removed.

[0030] Naturally, the temperature at this time is much lower than the temperature during conditioning in step S2, and is also sufficiently lower than the temperature for thermal desorption in step S5, which will be described later. Therefore, there is almost no effect on the target component adsorbed in the adsorption section 14. Note that, because the housing 33 and other components of the conditioning / solvent purge unit 3 are heated to a high temperature during conditioning, they will not drop to a temperature of approximately 30 to 40°C by natural heat dissipation during the processing of step S3. Therefore, the heating / cooling section 34 may cool the housing 33 and other components after conditioning is completed, thereby lowering the temperature to, for example, approximately 30 to 40°C. Of course, the heating / cooling section 34 may not perform cooling and may wait until the temperature drops by natural heat dissipation.

[0031] After the solvent removal process in step S4 has been performed for a predetermined time, thermal desorption is carried out in the vaporization chamber 50 of the GC device 5, and the target components adsorbed in the adsorption section 14 of the SPME Arrow 1 are carried by the flow of the carrier gas and introduced into the column 51. The various target components are separated in the time direction while passing through the column 51, and are each detected in the detection section 52 (step S5).

[0032] Specifically, the rod 13 of the SPME Arrow 1 is temporarily housed within the needle 12, and the main body moving unit 20 moves the SPME Arrow 1 to a component introduction position above the vaporization chamber 50 of the GC device 5. The plunger driving unit 21 pushes in the plunger 11, causing the tip of the rod 13 to pierce a septum at the top of the vaporization chamber 50 and insert the adsorption unit 14 into the vaporization chamber 50. At this time, since the vaporization chamber 50 is heated to a predetermined temperature (usually 200°C or higher), when the adsorption unit 14 is inserted into the vaporization chamber 50, the various target components adsorbed to the adsorption unit 14 volatilize in a short time. The volatilized target components are carried by the carrier gas and introduced into the column 51 almost simultaneously.

[0033] Because the flow rate of the carrier gas is small, the concentration of the target component in the gas is higher than when the sample was collected in step S3. That is, the target component is highly concentrated and introduced into column 51. This allows the target component to be detected with high sensitivity. Furthermore, because the solvent is removed from adsorption section 14 in step S4, the amount of solvent introduced into column 51 in step S5 is significantly reduced compared to the amount adsorbed in step S3. Therefore, peaks corresponding to the solvent hardly appear on the chromatogram created based on the detection signal from detection section 52. This reduces distortion of the waveform shape of the target component peak and shifts in retention time caused by the influence of a large amount of solvent introduced into column 51.

[0034] 2 is provided with unit 3 that performs both conditioning and solvent removal, it is also possible to provide separate units that perform conditioning and solvent removal. This configuration allows conditioning and solvent removal to be performed simultaneously in parallel, which may enable more efficient GC analysis of a large number of samples.

[0035] Furthermore, the ease (or difficulty) of volatilization of the solvent adsorbed in the adsorption section 14 varies depending on the type of adsorbent or liquid phase held in the adsorption section 14, the size of the SPME Arrow 1 (the size of the surface area of ​​the adsorption section 14), the type of solvent, etc. Therefore, it is desirable that the conditions for removing the solvent in step S4, such as the heating temperature, inert gas flow rate, and required time, be changed or adjusted as appropriate depending on the type of SPME Arrow 1 used and the type of solvent in the sample. If the type of SPME Arrow used is configured to be automatically determined, it is also possible to automatically control the conditions for removing the solvent, such as the heating temperature, inert gas flow rate, and required time, depending on the determination result.

[0036] The above embodiment is merely an example of the present invention, and it is clear that any modifications, changes, or additions made within the spirit and scope of the present invention will fall within the scope of the claims of the present application.

[0037] For example, although the SPME method is primarily used for sample introduction in GC analysis, it is also possible to use the SPME method for other analytical techniques, such as liquid chromatography (LC) analysis. Therefore, the sample introduction method and apparatus according to the present invention are not necessarily applicable only to GC analysis. However, in general, in LC analysis, water, organic solvents, etc. are unlikely to interfere with the analysis of the target component. In this respect, the sample introduction method and apparatus according to the present invention can be said to be particularly useful in GC analysis.

[0038] Various Aspects It will be apparent to those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

[0039] (Item 1) One aspect of the sample introduction method according to the present invention is a sample introduction method for collecting and injecting a sample by solid-phase microextraction using an SPME Arrow, comprising: an adsorption step of adsorbing a target component in the sample to the adsorption portion of the SPME Arrow; an exposure step of exposing the adsorption portion of the SPME Arrow after the adsorption step to a dry inert gas atmosphere for a predetermined time; and an injection step of heating the adsorption portion of the SPME Arrow after the exposure step to desorb the target component from the adsorption portion and introduce the target component into an analytical device.

[0040] (Item 4) One aspect of the sample introduction device according to the present invention is a device for carrying out the sample introduction method described in Item 1, and is a sample introduction device that uses an SPME Arrow to collect a sample by solid-phase microextraction and inject it into an analytical device, and includes: an adsorption treatment section that inserts the adsorption section of the SPME Arrow into a container in which the sample is sealed, and adsorbs a target component in the sample onto the adsorption section; an exposure treatment section that exposes the adsorption section of the SPME Arrow to a dry inert gas atmosphere for a predetermined time after component adsorption in the adsorption treatment section is completed; and a movement section that moves the SPME Arrow between the adsorption treatment section and the exposure treatment section, and between the exposure treatment section and a component introduction position where the target component adsorbed on the adsorption section is introduced into the analytical device.

[0041] In the sample introduction method described in paragraph 1, which is carried out using the sample introduction device described in paragraph 4, at least a portion of the solvent in the sample adsorbed to the adsorption section in the adsorption step is volatilized and removed from the adsorption section in the exposure step. This reduces the influence of solvents, such as water and organic solvents, derived from the sample during GC analysis, thereby preventing distortion of the chromatographic peak shape of the target component and shifts in retention time. This improves the quantification and identification performance of the target component.

[0042] (Item 2) In the sample introduction method described in item 1, the exposure step can involve heating the adsorption portion of the SPME Arrow to a temperature lower than the temperature at which it was heated in the injection step.

[0043] (Item 5) In the sample introduction device described in item 4, the exposure processing unit may include a heating unit that heats the adsorption unit of the SPME Arrow to a temperature at which the target component does not desorb.

[0044] According to the sample introduction method described in paragraph 2 and the sample introduction device described in paragraph 5, the removal of solvent from the adsorption section is promoted, thereby further reducing the influence of solvent derived from the sample during GC analysis and improving the accuracy of the analysis.

[0045] In the SPME method using SPME fiber or SPME arrow, conditioning is generally carried out prior to sample collection to remove impurities adhering to the adsorbent and residual components from the previous analysis.

[0046] (Item 3) Therefore, the sample introduction method described in Item 2 may further include a conditioning step of heating the adsorption portion of the SPME Arrow in an inert gas atmosphere prior to the adsorption step, and the heating temperature in the exposure step may be lower than the heating temperature in the conditioning step.

[0047] (Item 6) The sample introduction device described in Item 5 may further include a conditioning unit that cleans the adsorption unit of the SPME Arrow by heating the adsorption unit in an inert gas atmosphere, and the conditioning unit may also be used as the exposure treatment unit.

[0048] The sample introduction method described in paragraph 3 prevents impurities and residual components other than the target component from being introduced into the GC system, further improving the accuracy of analysis. Furthermore, the sample introduction device described in paragraph 6 can also remove the solvent using a conditioning unit, eliminating the need to add new components for solvent removal, thereby reducing the cost of the device. Furthermore, increases in the size and weight of the device can also be reduced.

[0049] REFERENCE SIGNS LIST 1 SPME Arrow 10 Holder 11 Plunger 12 Needle 13 Rod 14 Adsorption section 2 SPME Arrow drive section 20 Main body moving section 21 Plunger drive section 3 Conditioning / solvent purge unit 30 Housing 31 Gas supply opening 32 Gas exhaust opening 33 Recess 34 Heating / cooling section 4 Sample collection unit 5 GC device 50 Vaporization chamber 51 Column 52 Detection section

Claims

1. A sample introduction method for collecting and injecting a sample by solid-phase microextraction using an SPME Arrow, comprising: an adsorption step of adsorbing a target component in a sample to the adsorption portion of the SPME Arrow; an exposure step of exposing the adsorption portion of the SPME Arrow after the adsorption step to an atmosphere of dry inert gas for a predetermined period of time; and an injection step of heating the adsorption portion of the SPME Arrow after the exposure step to remove the target component from the adsorption portion and introduce it into an analytical device.

2. The sample introduction method according to claim 1, wherein in the exposure step, the adsorption portion of the SPME Arrow is heated to a temperature lower than the temperature at which it was heated in the injection step.

3. The sample introduction method according to claim 2, further comprising a conditioning step of heating the adsorption portion of the SPME Arrow in an inert gas atmosphere prior to the adsorption step, wherein the heating temperature in the exposure step is lower than the heating temperature in the conditioning step.

4. A sample introduction device that uses an SPME Arrow to collect samples by solid-phase microextraction and inject them into an analytical device, comprising: an adsorption processing unit that inserts the adsorption part of the SPME Arrow into a container in which a sample is sealed, and adsorbs a target component in the sample to the adsorption part; an exposure processing unit that exposes the adsorption part of the SPME Arrow to a dry inert gas atmosphere for a predetermined period of time after component adsorption in the adsorption processing unit is completed; and a moving unit that moves the SPME Arrow between the adsorption processing unit and the exposure processing unit, and between the exposure processing unit and a component introduction position where the target component adsorbed to the adsorption part is introduced into an analytical device.

5. The sample introduction device according to claim 4, wherein the exposure processing section includes a heating section for heating the adsorption section of the SPME Arrow to a temperature at which the target component is not released.

6. The sample introduction device according to claim 5, further comprising a conditioning section for cleaning the adsorption section of the SPME Arrow by heating the adsorption section in an inert gas atmosphere, the conditioning section also being used as the exposure treatment section.

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