Gas chromatographic analysis method and gas chromatographic analysis program

Abstract

One embodiment of a gas chromatograph (GC) analysis method according to the present invention, which employs a column to separate and detect components contained in sample gas, includes: a sample collecting step (S1-S3) for collecting the sample gas using a headspace method from a solution containing n-alkanes, which are reference compounds for a retention index; a reference compound analysis step (S3) for introducing the sample gas collected in the sample collecting step into the column to perform GC analysis; and a retention time calculating step (S4-S5) for obtaining actual measured retention times for the n-alkanes on the basis of a chromatogram obtained by the GC analysis, and estimating the retention time of a compound being analyzed, from said actual measured retention times and the known retention index of the compound being analyzed. In this way, in a GC analysis method in which sample introduction is performed using the headspace method, it is possible to perform highly accurate compound identification employing retention times corresponding to various compounds in the sample.

Description

[Technical Field]

[0001] The present invention relates to an analytical method using a gas chromatograph (GC) and a computer program for carrying out the analytical method, and more particularly to a GC analytical method and a GC analytical program that utilizes the headspace method for introducing a sample into a column. Note that the GC analysis referred to here includes gas chromatography / mass spectrometry (GC / MS) that uses a mass spectrometer as a detector. [Background technology]

[0002] In GC analysis, retention time (RT) is typically used to identify peaks observed in a chromatogram. However, retention time is not a compound-specific value; it varies depending on various separation conditions, such as carrier gas flow rate, column temperature, and column length. Therefore, accurate peak identification using retention time is impossible unless the separation conditions used to measure the target sample are identical to those used to measure the standard substance when the retention time used for identification was obtained. In many cases, this is practically impossible. Therefore, in GC analysis, the retention index (RI), which is less dependent on separation conditions and inter-instrumental differences, is often used instead of retention time. The retention index is an index of the retention times of various compounds using the retention times of the peaks of n-alkanes, which are reference compounds. Retention index values ​​are widely known for many compounds.

[0003] As described in Non-Patent Document 1, conventional GC instruments are equipped with a function that estimates the retention time of an analyte compound from the known retention index of the analyte compound, the retention index of the reference compound, and the retention time obtained by actually measuring the reference compound, and then uses the estimated value to correct the retention time of the analyte compound previously registered in the instrument. In the instrument described in Non-Patent Document 1, this function is called AART (Automatic Adjustment of Retention Time). This allows for accurate correction of the retention time of the analyte compound before the change in separation conditions to the appropriate value after the change, even if the separation conditions are changed, for example, when a portion of the column is cut due to column contamination. This improves the accuracy of identification of analyte compounds using retention times.

[0004] To utilize the automatic retention time correction function described above, users must actually measure the reference compounds on their own instrument. Typically, when measuring a reference compound, a predetermined amount of a standard reagent containing the reference compound is injected manually or using an autoinjector into the sample vaporization chamber at the inlet end of the column. The n-alkane standard reagent, which is the basis for the retention index, contains a wide variety of normal alkanes, ranging in carbon number from a few to over 30, and has a fairly wide range of boiling points. However, the sample components are vaporized in the sample vaporization chamber at high temperatures of approximately 200°C or higher, allowing a wide variety of normal alkanes to be efficiently vaporized and delivered to the column. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] "Automatic correction of retention time, input of retention index", [Online], [Retrieved December 23, 2021], Shimadzu Corporation, Internet<URL: https: / / www.an.shimadzu.co.jp / gcms / support / faq / gcmssol / faq12.htm> [Non-patent document 2] "Headspace Sampler HS-20 NX Series," [Online], [Retrieved December 23, 2021], Shimadzu Corporation, Internet<URL: https: / / www.an.shimadzu.co.jp / gc / hs-20nx / c180-0214.pdf> (First published: June 2021) Summary of the Invention [Problem to be solved by the invention]

[0006] Headspace (HS) is one of the sample introduction methods for GC analysis. In HS, a liquid or solid sample placed in a sealed sample container is heated to a constant temperature for a fixed period of time to volatilize the components in the sample. A fixed amount of sample gas containing these components is then collected from the headspace within the sample container and introduced into the column. Unlike sample introduction methods using a sample vaporizer, the HS method allows components to be volatilized and collected at relatively low temperatures, close to room temperature. For example, many of the aroma components in food and beverages and the odor components in chemical products are compounds with low boiling points, i.e., highly volatile compounds. By introducing these samples using the HS method, the aroma components of interest can be efficiently introduced into the column, while high-boiling-point impurities that are not of interest are less likely to be introduced into the column, allowing for a more accurate analysis without impurities.

[0007] For example, when analyzing odor components in a sample by combining a headspace sampler described in Non-Patent Document 2 with a GC device, the target sample is measured using the HS method, while a standard reagent containing n-alkanes is measured by injecting the reagent into a sample vaporization chamber installed at the inlet of the column. The measurement results for the standard reagent are used to correct the retention time of the target compound (odor component). However, different sample introduction methods can result in different retention times for the same compound even if other separation conditions are exactly the same, raising concerns about reduced accuracy in retention time correction. Reduced accuracy in retention time correction can reduce the accuracy of peak identification, i.e., compound identification. There is also a risk of missing unknown compounds contained in the sample.

[0008] The present invention was made in consideration of these problems, and one of its objectives is to identify compounds in a sample with high accuracy by utilizing the retention times corresponding to various compounds in the sample in a GC analysis method in which the sample is introduced by the HS method. [Means for solving the problem]

[0009] One aspect of the GC analysis method according to the present invention, which has been made to solve the above problems, is a GC analysis method for separating and detecting components contained in a sample gas using a column, comprising: a sampling step of collecting a sample gas from a solution containing an n-alkane, which is a reference compound for the retention index, using a headspace method; a reference compound analysis step in which the sample gas collected in the sample collection step is introduced into a column and analyzed by GC; a retention time calculation step of determining an actual retention time for an n-alkane based on a chromatogram obtained by the GC analysis in the reference compound analysis step, and estimating a retention time of the target compound from the actual retention time and a known retention index of the target compound; It has.

[0010] One aspect of the GC analysis program according to the present invention, which has been made to solve the above-mentioned problems, is a GC analysis program for controlling a system including a headspace sampler and a measurement unit that separates and detects components contained in a sample gas using a GC column, the program being programmed on a computer to: a reference compound measurement condition setting step of displaying a screen for setting measurement conditions including a vial oven temperature for measuring n-alkane, which is a reference compound for the retention index, in response to a user operation and accepting settings made by the user on the screen; a reference compound measurement step of controlling the headspace sampler and the measurement unit according to the measurement conditions set in the reference compound measurement condition setting step, and performing GC analysis of n-alkanes in a prepared vial; a retention time correction step of determining an actual retention time for an n-alkane based on a chromatogram obtained by GC analysis in the reference compound measurement step, estimating a retention time of the target compound from the actual retention time and a known retention index of the target compound, and correcting the retention time in a compound table that describes information about the target compound; This is what causes the following to be executed. [Effects of the Invention]

[0011] According to the above-described aspects of the GC analysis method and GC analysis program of the present invention, n-alkanes, which are reference compounds, are analyzed by GC using the HS method, as well as target compounds. This allows the retention times of the target compounds to be acquired or corrected with high accuracy. This allows for highly accurate identification of target compounds using retention times. Furthermore, unlike conventional methods, the task of changing the system configuration between measuring the reference compounds and measuring the target compounds—specifically, the task of attaching and detaching a headspace sampler or a sample vaporization chamber—is no longer necessary. Therefore, the measurement of the reference compounds and the measurement of the target compounds can be performed using a system with the same configuration. This reduces the user's workload and improves measurement efficiency. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic block diagram showing an example of a GC-MS system for carrying out a GC analysis method according to one embodiment of the present invention. [Figure 2] 2 is a flowchart showing the procedure for identifying a target compound for analysis, including automatic correction processing of retention times, in the GC-MS system shown in FIG. 1. [Figure 3] 1 is a flowchart showing the procedure for measuring a reference compound. DETAILED DESCRIPTION OF THE INVENTION

[0013] An embodiment of a GC analysis method and a computer program for implementing the method according to the present invention will be described with reference to the accompanying drawings.

[0014] [GC-MS system configuration] FIG. 1 is a schematic block diagram showing an example of a GC-MS system for carrying out the GC analysis method of this embodiment.

[0015] This GC-MS system includes a headspace sampler (sometimes abbreviated as HSS) 1, a measurement unit 2 including a gas chromatograph unit (GC unit) 3 and a mass spectrometer unit (MS unit) 4, a control and processing unit 5 that controls the headspace sampler 1 and the measurement unit 2 and processes the data (mass spectrum data, chromatogram data) obtained by the measurement unit 2, a main control unit 6 that controls the entire system, and an input unit 7 and display unit 8 that serve as user interfaces.

[0016] Although not shown, the headspace sampler 1 includes a vial oven that heats a vial containing a liquid (or solid) and a sample collection unit that includes a syringe that draws in and discharges a predetermined amount of sample gas from the headspace inside the vial. The headspace sampler 1 may also include a changer mechanism that selects a number of pre-prepared vials in a predetermined (programmed) order and sets them in the vial oven. For example, the Shimadzu Corporation "HS-20 NX Series" headspace sampler (see Non-Patent Document 2) can be used as the headspace sampler 1.

[0017] Although not shown, the GC section 3 in the measurement section 2 includes a column that separates components in the sample gas, a column oven that controls the temperature of the column, and a gas supply section that supplies a constant flow rate of carrier gas to the column.

[0018] The MS unit 4 includes an ion source that continuously ionizes components in the sample gas sent from the GC unit 3, a mass separator such as a quadrupole mass filter that separates ions according to their mass-to-charge ratio (m / z), and a detector that detects the ions. Instead of a single-type quadrupole mass spectrometer, the MS unit 4 may be a mass spectrometer capable of MS / MS analysis, such as a triple quadrupole mass spectrometer or a quadrupole-time-of-flight mass spectrometer. Since the important point here is that GC analysis is performed, the measurement unit 2 may not be a GC-MS, but may be a GC device using various detectors other than a mass spectrometer.

[0019] The control and processing unit 5 includes functional blocks such as a measurement control unit 51, a method creation and editing unit 52, a method storage unit 53, a retention time correction processing unit 54, an identification processing unit 55, and a data storage unit 56. The method storage unit 53 stores at least a reference compound measurement method and an analyte compound measurement method. The data storage unit 56 stores at least reference compound measurement data and analyte compound measurement data.

[0020] The control / processing unit 5 and the main control unit 6 can realize their respective functions by using a personal computer as a hardware resource and running dedicated control / processing software (computer program) installed on the computer.

[0021] This computer program may be a single piece of software that is integrated into one package, but it can usually consist of multiple pieces of software, such as basic control and processing software that controls the headspace sampler 1 and measurement unit 2 and processes the data obtained by measurement unit 2, and a method package, which is software that includes a compound table containing information about various compounds for specific purposes, such as for pesticide residue testing or metabolite testing, and methods such as measurement and analysis conditions for measuring and analyzing these compounds.

[0022] The computer program may be provided to the user by being stored on a non-transitory computer-readable recording medium such as a CD-ROM, DVD-ROM, memory card, or USB memory (dongle). The program may also be provided to the user in the form of data transfer via a communication line such as the Internet. Furthermore, the program may be pre-installed on a computer that is part of the system (strictly speaking, a storage device that is part of the computer) when the user purchases the system.

[0023] The GC-MS system described above is capable of identifying (qualitatively) and quantifying various compounds in a sample, but as an example, we will explain the series of steps and processing performed in the system when identifying various odor-related compounds to evaluate the odor of a sample such as food or drink. Note that the term "odor" here refers to odor in a broad sense, including aroma and odor.

[0024] Compounds related to odors (hereinafter referred to as "odor-related compounds") are often compounds that easily volatilize at relatively low temperatures (room temperature or slightly higher). However, samples usually contain not only odor-related compounds but also compounds that are completely unrelated to odors. To accurately evaluate odors, it is desirable to qualitatively and quantitatively analyze odor-related compounds while eliminating as many unrelated compounds as possible. The HS method allows heating over a wide temperature range, from relatively low to high temperatures, making it a sampling method that meets the above-mentioned objectives and is suitable for detecting trace amounts of odor-related compounds in samples with high sensitivity.

[0025] Here, in order to comprehensively analyze odor-related compounds, a compound table containing information about various odor-related compounds and a method package containing methods such as analytical conditions for the analysis are used. The reference compound measurement method and the analyte compound measurement method stored in the method storage unit 53 are provided as part of the method package. Furthermore, the compound table included in the analyte compound measurement method contains information necessary for compound measurement and identification, such as mass, retention time, retention index, and m / z value, for each of the various analyte compounds (here, odor-related compounds).

[0026] When identifying odor-related compounds in a target sample, for example, prior to measuring the target sample, automatic retention time correction processing is performed as follows: Figure 2 is a flowchart showing the identification procedure, including automatic correction processing of the retention time of the target compound, in the above-mentioned GC-MS system.

[0027] To measure a reference compound, the user first creates a measurement method for the reference compound (step S1). Here, the reference compound measurement method is stored in the method storage unit 53 as part of the method package, so the user's only task is to modify some of the measurement conditions, etc., as necessary, as described below. Then, the user prepares a vial containing a solution containing an n-alkane, the reference compound, as a sample for measurement, according to the measurement conditions (step S2).

[0028] The user loads the prepared vial into the headspace sampler 1 and performs a predetermined operation on the input unit 7. This causes the measurement control unit 51 to control the headspace sampler 1 and the measurement unit 2 according to the reference compound measurement method stored in the method storage unit 53, and performs measurement (GC / MS analysis) of the n-alkane, which is the reference compound (step S3).

[0029] 3 is a flowchart showing the detailed procedure of the processes corresponding to the above steps S1 to S3. An example of the procedure of steps S1 to S3 will be described in detail with reference to FIG. When performing measurements by the HS method using the headspace sampler 1, the user selects one of two sample introduction methods in the reference compound measurement method. The two sample introduction methods are the standard method and the high-precision method, and the differences between them will be explained later.

[0030] The user performs a predetermined operation on the input unit 7 to open the headspace sampler (HSS) setting screen (step S21). If the user wishes to perform retention time correction processing with standard accuracy using the measurement results of the reference compound (Yes in step S22), the user selects the standard method on the setting screen (step S23). On the other hand, if the user wishes to correct the retention time of the target compound with high accuracy using the measurement results of the reference compound (No in step S22), the user selects the high-precision method on the setting screen (step S26).

[0031] If the standard method is selected, the user sets the vial oven temperature, one of the important measurement conditions for the headspace sampler 1, to an appropriate temperature value within the range of 10 to 99°C, often within the range of 40 to 80°C, and more preferably within the range of 40 to 60°C (step S24). The method creation / editing unit 52 accepts the set temperature value as part of the reference compound measurement method and stores it within or in association with the method. The user then prepares a measurement sample by dissolving a predetermined amount of n-alkane standard reagent in a predetermined amount of water and sealing the solution in a vial (step S25). In other words, in this case, the measurement sample prepared in step S2 above is a standard reagent dissolved in water.

[0032] On the other hand, if the high-precision method is selected instead of the standard method, the user sets the vial oven temperature to an appropriate temperature value within the range of 150 to 220°C (step S27). The method creation / editing unit 52 accepts the set temperature value as part of the reference compound measurement method and stores it within or in association with the method. The user then prepares a measurement sample by sealing a trace amount (e.g., about 1 to 2 μL) of n-alkane standard reagent into a vial (step S28). In other words, in this case, the measurement sample prepared in step S2 above is not a sample dissolved in water, but a trace amount of pure standard reagent.

[0033] Next, the user issues an instruction to start measurement execution, for example, via the input unit 7. Under the control of the measurement control unit 51 that receives this instruction, the headspace sampler 1 heats the vial to the specified vial oven temperature and maintains that temperature for a predetermined period of time. A portion of the sample gas containing n-alkanes that fills the internal space of the vial is introduced into the GC unit 3 via the carrier gas flow. As the sample gas passes through the column of the GC unit 3, the n-alkanes in the gas are separated over time according to their carbon number. The MS unit 4 sequentially detects the n-alkanes separated over time in the GC unit 3 and outputs a detection signal corresponding to their concentration. The measurement data obtained for the n-alkanes is stored in the data storage unit 56 in the control and processing unit 5.

[0034] Here, the difference between the standard method and the high precision method will be explained. n-alkane standard reagents contain a wide variety of straight-chain alkanes, ranging in carbon number from a few to over 30. As an example, the "Qualitative Retention Time Index Standard" sold by GL Sciences Inc. contains n-alkanes with different carbon numbers, from C7 to C33. The boiling point of straight-chain alkanes increases with the number of carbon atoms, and temperatures of 200°C or higher are required to volatilize all of the straight-chain alkanes contained in the standard reagent.

[0035] Many of the odor-related compounds analyzed in this example are low-boiling compounds that readily volatilize at room temperature. On the other hand, samples containing odor-related compounds also contain many impurities with relatively high boiling points. Therefore, to measure odor-related compounds with high sensitivity and accuracy, it is desirable to use the HS method at a relatively low temperature, specifically, a temperature of approximately 10 to 99°C (typically approximately 40 to 60°C), at which odor-related compounds volatilize while most impurities do not.

[0036] If the HS method is used at a high temperature of 200°C or higher when measuring a standard reagent containing n-alkanes, then when attempting to measure a target sample following the measurement of the standard reagent, it is necessary to wait until the temperature of the vial oven of the headspace sampler 1 drops, resulting in wasted waiting time and reduced analytical efficiency. In contrast, if the HS method is used at a temperature similar to that used when measuring the target sample when measuring a standard reagent containing n-alkanes, such wasted waiting time is eliminated, and analytical efficiency can be improved.

[0037] In other words, when analytical efficiency is important, it is preferable to perform measurements using the standard method, which uses a low vial oven temperature, rather than the high-precision method. In this case, to facilitate the vaporization of n-alkanes even at low temperatures, it is desirable to dissolve the standard reagent in water rather than using it as is. Because only linear alkanes with carbon numbers lower than the C16 in the standard reagent volatilize in the standard method, the chromatographic peaks of linear alkanes with higher carbon numbers, which have longer retention times than these linear alkanes, cannot be used for retention time correction. Therefore, although the accuracy of the retention time estimation for analyte compounds with relatively long retention times may be slightly lower, in most cases, this decrease in accuracy is not a practical problem.

[0038] On the other hand, for example, when analyte compounds with relatively long retention times are important, it may be necessary to precisely correct the retention times of these compounds in order to accurately identify them. In such cases, measurement using the high-precision method can be selected instead of the standard method. When the vial is heated to approximately 200°C in the HS method, bumping may occur if a certain amount of water is contained in the vial. Therefore, in the high-precision method, it is desirable to place a small amount of standard reagent directly in the vial without dissolving it in water.

[0039] As mentioned above, the high-precision method has the disadvantage that unnecessary waiting time is required to lower the temperature of the vial oven in the headspace sampler 1, because the vial heating temperature in the HS method differs significantly between n-alkane measurement and target sample measurement. On the other hand, the high-precision method has the advantage that the chromatographic peaks derived from almost all of the normal alkanes contained in the standard reagent can be used to estimate the retention times of the analyte compounds, allowing the retention times of the analyte compounds to be estimated and corrected with high accuracy.

[0040] Returning to FIG. 2 , the explanation will continue from step S4. As described above, once the measurement of the n-alkane reference compound is completed and the measurement data is stored in the data storage unit 56, the retention time correction processor 54 creates a chromatogram based on the reference compound measurement data and detects peaks in the chromatogram. Then, using a compound table of the reference compound included in the reference compound measurement method, the retention time correction processor 54 identifies chromatographic peaks corresponding to the n-alkane (step S4). Furthermore, the retention time correction processor 54 acquires the retention times of each identified chromatographic peak and corrects the retention times of each n-alkane in the compound table of the reference compound to their actual measured values ​​(step S5). As a result, the retention times in the compound table of the reference compound reflect the latest measurement conditions. Even if the column length has changed since the previous measurement due to, for example, column disconnection, the retention times are corrected to reflect the new column length.

[0041] Next, the retention time correction processing unit 54 reads out the compound table of the analyte compounds included in the analyte compound measurement method stored in the method storage unit 53, and estimates the retention time of each analyte compound using the retention index of each analyte compound in the compound table and the measured retention index and retention time of each reference compound in the compound table of the reference compounds (step S6).Then, based on the estimation result, the retention time of each analyte compound in the compound table of the analyte compounds is corrected (step S7).

[0042] The method for calculating the retention time is the same as the conventional automatic correction process for retention time described in Non-Patent Document 1 and the like. Specifically, if the peak of the target compound is between the peak of the nth linear alkane and the peak of the (n+1)th linear alkane on the chromatogram, the retention time of the target compound can be calculated using the following formula (1). RT T =RT vn +(RT vn+1 -RT vn )×{(RI T -RI vn ) / (RI vn+1 -RIvn )} …(1) RT T : Retention time of the analyte RI T : Retention index of the analyte RT vn : Retention time of the nth reference compound (actual value) RI vn : Retention index of the nth reference compound RT vn+1 : Retention time of the n+1th reference compound (actual value) RI vn+1 : Retention index of the n+1th reference compound

[0043] For example, when the above-mentioned standard method is used in measuring the reference compounds, chromatographic peaks of some of the reference compounds are not detected, and therefore, there are no peaks of the reference compounds sandwiching the analyte compound therebetween. In this case, the retention time can be calculated by assuming that the peaks of the reference compounds exist at the intervals corresponding to the retention times and retention indices of the two reference compounds that are closest in time to the analyte compound.

[0044] If necessary, the user can check the retention times automatically corrected as described above on the screen of the display unit 8 (step S8). In response to a user instruction via the input unit 7, the method creation / editing unit 52 stores a file of the analyte compound measurement method including the compound table with the corrected retention times in the method storage unit 53 (step S9).

[0045] Next, in response to a predetermined operation performed by the user, the measurement control unit 51 performs measurement (GC / MS analysis) of the target sample by controlling the headspace sampler 1 and the measurement unit 2 according to the analyte compound measurement method stored in the method storage unit 53 (step S10). In this measurement, the temperature of the vial oven in the headspace sampler 1 is set within the range of 10 to 99°C. The measurement data obtained by the GC / MS analysis of the target sample is stored in the data storage unit 56.

[0046] Thereafter, the identification processing unit 55 creates a chromatogram based on the analyte compound measurement data stored in the data storage unit 56, detects peaks in the chromatogram, and identifies the analyte compounds by identifying the chromatographic peaks derived from each analyte compound using the analyte compound table with the corrected retention times (step S11).

[0047] In this identification process, the retention times corrected using the measurement results of the reference compounds obtained by the HS method, the same as when measuring the target sample, are used, so each compound can be identified with higher accuracy than when using retention times calculated based on the measurement results of the reference compounds obtained by the sample introduction method using a sample vaporization chamber. This makes it possible to avoid situations where compounds cannot be identified even though they are detected, or where identification errors occur.

[0048] It should be noted that the GC analysis method and GC analysis program described above are merely examples of the present invention, and it is clear that any modifications, changes, or additions made within the spirit of the present invention will also fall within the scope of the claims of the present application.

[0049] [Various aspects] It will be apparent to those skilled in the art that the above-described exemplary embodiments are examples of the following aspects.

[0050] (Item 1) One aspect of the GC analysis method according to the present invention is a GC analysis method for separating and detecting components contained in a sample gas using a column, comprising: a sampling step of collecting a sample gas from a solution containing an n-alkane, which is a reference compound for the retention index, using a headspace method; a reference compound analysis step in which the sample gas collected in the sample collection step is introduced into a column and analyzed by GC; a retention time calculation step of determining an actual retention time for n-alkanes based on a chromatogram obtained by GC analysis, and estimating a retention time of the target compound from the actual retention time and a known retention index of the target compound; It has.

[0051] (Item 9) One aspect of the GC analysis program according to the present invention is a GC analysis program for controlling a system including a headspace sampler and a measurement unit that separates and detects components contained in a sample gas using a GC column, the program being configured on a computer to: a reference compound measurement condition setting step of displaying a screen for setting measurement conditions including a vial oven temperature for measuring n-alkane, which is a reference compound for the retention index, in response to a user operation and accepting settings made by the user on the screen; a reference compound measurement step of controlling the headspace sampler and the measurement unit according to the measurement conditions set in the reference compound measurement condition setting step, and performing GC analysis of n-alkanes in a prepared vial; a retention time correction step of determining an actual retention time for an n-alkane based on a chromatogram obtained by GC analysis, estimating a retention time of the target compound from the actual retention time and a known retention index of the target compound, and correcting the retention time in a compound table containing information about the target compound; This is what causes the following to be executed.

[0052] According to the GC analysis method described in paragraph 1 and the GC analysis program described in paragraph 9, n-alkanes are also analyzed by GC using the headspace method in the same way as target compounds, so the retention times of the target compounds are obtained or corrected with high accuracy. This allows for highly accurate identification of target compounds using retention times. Furthermore, unlike conventional methods, the task of changing the system configuration between measuring reference compounds and target compounds—specifically, the task of attaching and detaching a headspace sampler or a sample vaporization chamber in a GC instrument—is no longer necessary. Therefore, the measurement of reference compounds and target compounds can be performed using a system with the same configuration. This reduces the user's workload and improves measurement efficiency.

[0053] (Item 2) In the GC analysis method described in item 1, the retention time calculation step may be configured to use the estimated retention time of the target compound to correct the retention time in a compound table that contains information about the target compound.

[0054] According to the GC analysis method described in paragraph 2, the retention times of each analyte compound set based on actual measurements before a change in separation conditions, such as before column disconnection, can be corrected to accurate retention times that reflect the latest instrument conditions after column disconnection.

[0055] (Item 3) The GC analysis method according to item 1 or 2, an analyte component analysis step of performing gas chromatographic analysis on the sample gas collected from the target sample using a headspace method; a peak identification step of identifying peaks detected in the chromatogram obtained by the analysis step using the retention times estimated or corrected in the retention time calculation step; The above structure may further include:

[0056] (Item 10) The GC analysis program according to item 9 is also installed on a computer. an analysis target component analysis step of performing gas chromatographic analysis on sample gas collected from a target sample using a headspace method by controlling the headspace sampler and the measurement unit; a peak identification step of identifying peaks detected in the chromatogram obtained by the analyte component analysis step, using the retention times corrected in the retention time correction step; The above may be further executed.

[0057] According to the GC analysis method described in item 3 and the GC analysis program described in item 10, accurate retention time information reflecting the latest instrument status can be used to accurately identify target compounds in a target sample. In other words, identification errors, inability to identify, or missed identifications can be reduced, enabling highly accurate compound identification.

[0058] (Item 4) In the GC analysis method according to any one of Items 1 to 3, the sample collection step can involve heating a container containing a solution of n-alkane dissolved in water to a temperature within a range of 10 to 99°C.

[0059] Dissolving n-alkanes in water can facilitate volatilization of n-alkanes even at relatively low temperatures. For food and beverages, sampling using the headspace method is often performed at temperatures ranging from approximately 10 to 99°C (usually ranging from approximately 40 to 60°C). However, the GC analysis method described in Section 4 allows sampling of n-alkanes using the headspace method at approximately the same temperature as that of the target sample. This allows GC analysis of the target sample and GC analysis of n-alkanes to be performed without any time delay, allowing efficient identification and quantification of the target compounds in the target sample.

[0060] (Item 5) In the GC analysis method described in any one of Items 1 to 3, the sample collection step can involve heating a container containing a trace amount of n-alkane to a temperature within a range of 150 to 220°C.

[0061] (Item 6) In the GC analysis method described in Item 5, the sample collection step can involve heating a container containing a trace amount of n-alkane to a temperature within a range of 190 to 210°C.

[0062] According to the GC analysis method described in items 5 or 6, n-alkanes of C20 or higher contained in general n-alkane mixed solutions can be detected with sufficient sensitivity, and the identification results of such n-alkanes can be used to accurately estimate the retention times of analyte compounds having retention times similar to those of the n-alkanes.

[0063] (Item 7) The GC analysis method according to item 5 or 6, An analyte component analysis step in which a sample gas collected from a target sample using a headspace method at a temperature in the range of 10 to 99 ° C is subjected to gas chromatographic analysis; a peak identification step of identifying peaks detected in the chromatogram obtained by the analysis step using the retention times estimated or corrected in the retention time calculation step; The above structure may further include:

[0064] In the GC analysis method described in Section 7, as described above, the GC analysis of the target sample and the GC analysis of n-alkanes are carried out by the headspace method at approximately the same temperature. This allows these GC analyses to be carried out substantially consecutively without any time interval, allowing for efficient identification and quantification of the target compounds in the target sample.

[0065] (Item 11) The GC analysis program according to item 9 or 10 may be configured such that, in the step of setting reference compound measurement conditions, a first sampling mode in which the heating temperature in the headspace sampler is within a range of 10 to 99°C and a second sampling mode in which the heating temperature is within a range of 150 to 220°C can be selected.

[0066] As mentioned above, when the heating temperature of the headspace sampler is within the range of 10 to 99 °C, the heating temperature is approximately the same as that of the target sample, allowing for efficient operation. However, in this case, n-alkanes with a large carbon number (generally C17 or higher) in the n-alkane mixed solution are not detected with sufficient sensitivity, resulting in relatively low accuracy in estimating the retention times of analyte compounds with long retention times. In contrast, when the heating temperature of the headspace sampler is within the range of 150 to 220 °C, n-alkanes with a large carbon number in the n-alkane mixed solution can be detected with sufficient sensitivity, allowing for accurate estimation of the retention times of analyte compounds with long retention times. However, in this case, the heating temperatures of the headspace sampler are significantly different between n-alkanes and the target sample, making it difficult to perform continuous GC analysis of both, which is disadvantageous in terms of analytical efficiency.

[0067] In the GC analysis program described in paragraph 11, the user can select the first sampling mode when prioritizing analytical efficiency, or the second sampling mode when prioritizing identification accuracy over analytical efficiency, depending on the purpose of analysis, the type of target sample, etc. This allows for easy analysis that meets the user's needs.

[0068] (Item 8) In the GC analysis method according to any one of items 1 to 7, the compound to be analyzed may be a compound related to an odor.

[0069] (Item 12) Similarly, in the GC analysis program according to any one of Items 9 to 11, the target compound to be analyzed can be a compound related to an odor.

[0070] According to the GC analysis method described in item 8 and the GC analysis program described in item 12, odor-related compounds that are generally highly volatile (i.e., have low boiling points) can be accurately identified. [Explanation of symbols]

[0071] 1. Headspace sampler 2...Measuring part 3...Gas chromatograph section (GC section) 4...Mass spectrometry section (MS section) 5...Control and processing section 51...Measurement control section 52...Method Creation / Editorial Department 53...Method storage section 54...Retention time correction processing section 55...Identification processing unit 56...Data storage unit 6...Main control unit 7...Input section 8…Display section

Claims

1. A gas chromatographic analysis method for separating and detecting components contained in a sample gas using a column, comprising: a sampling step of collecting a sample gas from a solution containing an n-alkane, which is a reference compound for the retention index, using a headspace method; a reference compound analysis step in which the sample gas collected in the sample collection step is introduced into a column and analyzed by gas chromatography; a retention time calculation step of determining an actual retention time for an n-alkane based on a chromatogram obtained by the gas chromatographic analysis in the reference compound analysis step, and estimating a retention time of the target compound in gas chromatographic analysis using a headspace method for sample introduction from the actual retention time and a known retention index of the target compound; A gas chromatographic analysis method comprising:

2. 2. The gas chromatographic analysis method according to claim 1, wherein the retention time calculation step uses the estimated retention time of the target compound to correct the retention time in a compound table that describes information about the target compound.

3. an analyte component analysis step of performing gas chromatographic analysis on the sample gas collected from the target sample using a headspace method; a peak identification step of identifying peaks detected in the chromatogram obtained by the analysis step using the retention times estimated or corrected in the retention time calculation step; 10. The gas chromatography analysis method of claim 1, further comprising:

4. 2. The gas chromatography analysis method according to claim 1, wherein in the sample collection step, a container containing a solution of n-alkane dissolved in water is heated to a temperature within a range of 10 to 99°C.

5. 2. The gas chromatography analysis method according to claim 1, wherein in the sample collection step, a container containing a trace amount of n-alkane is heated to a temperature within a range of 150 to 220°C.

6. 6. The gas chromatography analysis method according to claim 5, wherein in the sample collection step, a container containing a trace amount of n-alkane is heated to a temperature within a range of 190 to 210°C.

7. an analyte component analysis step in which sample gas collected from a target sample using a headspace method at a temperature in the range of 10 to 99°C is subjected to gas chromatographic analysis; a peak identification step of identifying peaks detected in the chromatogram obtained by the analysis step using the retention times estimated or corrected in the retention time calculation step; 6. The gas chromatographic analysis method of claim 5, further comprising:

8. 2. The gas chromatographic analysis method according to claim 1, wherein the compound to be analyzed is a compound related to an odor.

9. A gas chromatograph analysis program for controlling a system including a headspace sampler and a measurement unit that separates and detects components contained in a sample gas using a gas chromatograph column, the program comprising: a reference compound measurement condition setting step of displaying a screen for setting measurement conditions including a vial oven temperature for measuring n-alkane, which is a reference compound for the retention index, in response to a user operation and accepting settings made by the user on the screen; a reference compound measurement step of controlling the headspace sampler and the measurement unit in accordance with the measurement conditions set in the reference compound measurement condition setting step, and performing gas chromatographic analysis of n-alkanes in the prepared vial; a retention time correction step of determining an actual retention time for an n-alkane based on a chromatogram obtained by the gas chromatographic analysis in the reference compound measurement step, estimating a retention time of the target compound in a gas chromatographic analysis using a headspace method for sample introduction from the actual retention time and a known retention index of the target compound, and correcting the retention time in a compound table describing information about the target compound; A gas chromatograph analysis program that executes the above.

10. On the computer, an analyte component analysis step of performing gas chromatographic analysis on sample gas collected from a target sample using a headspace method by controlling the headspace sampler and the measurement unit; a peak identification step of identifying peaks detected in the chromatogram obtained by the analyte component analysis step, using the retention times corrected in the retention time correction step; 10. The gas chromatograph analysis program according to claim 9, further comprising:

11. 10. The gas chromatograph analysis program according to claim 9, wherein in the reference compound measurement condition setting step, a first sampling mode in which the heating temperature in the headspace sampler is within a range of 10 to 99°C and a second sampling mode in which the heating temperature is within a range of 150 to 220°C can be selected.

12. 10. The gas chromatographic analysis program according to claim 9, wherein the target compound is a compound related to an odor.

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