JP2006292446A - Gas chromatograph device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide precisely information on necessity of partial removal or replacement of a column by evaluating deterioration of the column simply and objectively. <P>SOLUTION: A retention index is determined and stored in a storage part 12 on the basis of data acquired by performing GC analysis of a prescribed material in the normal state having no column 5 deterioration. When evaluating the column deterioration after repeating analysis thereafter, a reference material having the retention index and the prescribed material are subjected to GC analysis, and the retention index at that time is calculated thereby. A column deterioration evaluation processing part 11 determines the difference between the retention index at the present time and the reference retention index stored in the storage part 12. When the difference exceeds a tolerance set beforehand, the column 5 is determined to be deteriorated, and the effect is displayed on a display part 9. Since the column deterioration is evaluated on the basis of the retention index, accurate evaluation can be performed without being influenced by the difference of an analysis condition. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a gas chromatograph apparatus that separates and analyzes sample components using a column.

  In gas chromatograph (GC) analysis, columns of various types and sizes are used depending on the type of sample and the purpose of analysis. These columns become contaminated with solvents and high-concentration samples while they are used for analysis, and gradually deteriorate. When the column deteriorates, the separation performance of the sample deteriorates, and peaks of a plurality of compounds overlap and cannot be separated, or the retention time may deviate more than the time assumed in advance, thereby hindering component identification. is there. Further, when the column deteriorates, the sample tends to remain on the inner wall of the column, and there is a concern that the residue is eluted and detected as a kind of impurity during the next analysis. For this reason, when the column is deteriorated so as to affect the analysis, it is necessary to cut a predetermined length of the inlet portion having a particularly large deterioration, or to discard the column and replace it with a new one.

  The degree of deterioration of the column can be obtained by calculating the resolution, but since such calculation is quite complicated and troublesome, it is actually not performed. In general, it is a method of managing usage history information such as usage time and usage frequency for each column, and partially cutting or replacing the column if it is used for a predetermined time or number of times. . A method of strictly managing the use history information of such a column is conventionally known from, for example, Patent Document 1.

  However, since the degree of deterioration of the column varies depending on the use conditions (analysis conditions) and the like, even if the use history is completely managed, for example, the degree of deterioration of two columns used for the same time is not necessarily the same. In addition, since the required resolution varies depending on the purpose of analysis, a column that can still be used by a certain user (analyst) cannot be used because sufficient performance cannot be obtained for other users. There is. Therefore, the determination as to whether or not a column that has been used for a certain period of time or a certain number of times can still be used is largely dependent on the experience and intuition of the analyst.

  Therefore, if the analyst's experience is inadequate, accurate judgment cannot be made. Actually, even when the column can still be used without problems, the column may be cut or replaced, or the column may deteriorate so that the analysis will be hindered. However, there is a problem that analysis is performed using a column as it is, and inappropriate analysis results are collected.

  On the other hand, when determining whether or not a column can be used as it is by uniformly determining the column usage time and the number of times used, etc. Even if it can withstand the use sufficiently, there is a high possibility that the column will be cut or replaced, and the running cost will increase accordingly.

JP 2004-163339 A

  If the degree of deterioration of the column can be evaluated simply and objectively, the above-described problems can be solved. The present invention has been made in view of the above points, and an object of the present invention is to provide a gas chromatograph apparatus that can evaluate the deterioration of a column more objectively and with high accuracy. .

  In order to solve the above problems, the gas chromatograph apparatus according to the present invention is almost independent of analysis conditions such as column size, column liquid phase film thickness, carrier gas flow rate, column temperature, and individual differences between apparatuses, Deterioration of the column is evaluated using a retention index (retention index) that depends mainly on the properties of the stationary phase of the column (for example, the liquid phase on the inner wall of the column).

That is, the gas chromatograph apparatus according to the present invention is
a) storage means for storing, as a reference holding index, a holding index of a predetermined substance related to a reference substance, which is obtained by gas chromatographic analysis using a normal column;
b) a retention index calculating means for calculating a retention index of the predetermined substance at the present time based on data obtained by performing a gas chromatographic analysis on the predetermined substance and the reference substance by the apparatus;
c) column evaluation means for evaluating the degree of deterioration of the column based on the difference or ratio between the reference holding index stored in the storage means and the current holding index calculated by the holding index calculation means;
d) Information providing means for providing the analyst with information based on the evaluation result by the column evaluation means;
It is characterized by having.

  Here, the “normal column” refers to a column that can be regarded as having no deterioration since the stationary phase (liquid phase) is the same as or equivalent to the column to be evaluated by the apparatus.

  In the gas chromatograph apparatus according to the present invention, the reference substance and the predetermined substance can be appropriately selected. Preferably, the predetermined substance is a substance having a property different from that of the reference substance with respect to the interaction with the stationary phase of the column. It is good to do. As a specific embodiment, the reference substance may be n-alkane, and the predetermined substance may be a substance having properties different from those of the n-alkane with respect to the interaction with the stationary phase of the column, for example, a polycyclic aromatic compound.

  As described above, the retention index mainly depends on the nature of the stationary phase of the column. Since the deterioration of the column can be understood as a change in the properties of the stationary phase, the retention index changes as the column deteriorates. Therefore, in the gas chromatograph apparatus according to the present invention, when the column is normal (that is, when it is not degraded), the reference retention index is retained in the storage means, and when it is necessary to evaluate the degradation of the column, The retention index calculation means calculates a retention index of the predetermined substance at the present time based on data obtained by performing gas chromatographic analysis on the predetermined substance and the reference substance. Since the retention index is hardly affected by the difference in the analysis conditions except for the change of the stationary phase of the column, the setting of the analysis conditions may not be exact.

  Since the retention index changes as the deterioration of the column progresses, the column evaluation means calculates the difference or ratio between the reference retention index stored in the storage means and the current retention index. For example, the calculated value is When the value is larger than a preset value, it is determined that the column has deteriorated so much that it interferes with the analysis. In this case, the information providing means performs a display on the screen of the display unit that recommends, for example, cutting the column inlet end or replacing the column.

  As described above, according to the gas chromatograph apparatus of the present invention, it is not an indirect indicator such as the column usage time and the number of times of use as in the prior art, but information on the column more accurately reflecting the deterioration state of the column. The degree of deterioration can be determined easily and accurately. As a result, it is possible to prevent the column from being cut or exchanged even though the column is not deteriorated so much and it is not necessary to cut or exchange, and the running cost can be reduced by effectively using the column. Conversely, when the column is considerably deteriorated and there is a possibility that the analysis may be hindered, it is possible to reliably cut or replace the column in advance, thereby avoiding unnecessary analysis.

  The reference retention index may be obtained from data obtained by actually performing gas chromatographic analysis. For example, if n-alkane is used as a reference substance, a huge database has already been widely provided. Therefore, the retention index recorded in such a database may be used as it is.

  In addition, when the difference between the reference retention index and the current retention index is large, the deterioration of the column is often the cause, but other causes are not unthinkable. For example, if the gas flow rate fluctuates during analysis due to gas leakage from a carrier gas flow path or the like, or a malfunction of a control unit (for example, a pressure valve) that controls the carrier gas flow rate, the retention index may change. Therefore, the information providing means may be configured to provide information indicating the possibility of fluctuation in the flow rate of the carrier gas flowing through the column, in addition to information indicating the possibility of malfunction of the column, based on the evaluation result by the column evaluating means. .

  According to this configuration, the analyst's attention is alerted, for example, first, it is checked whether there is a problem that may lead to fluctuations in the flow rate of the carrier gas. In conclusion, appropriate measures such as cutting the inlet end of the column or replacing the column with a new one can be taken.

  First, before describing this embodiment, a retention index (sometimes referred to as a retention index) in GC analysis will be briefly described with reference to FIG. Here, consider the case where the most common n-alkane homologue series is the reference substance.

Now, with reference to the appearance position of the peak of methane (CH ₄ ), which is a substance having little interaction with the column, in the chromatogram shown in FIG. 4, the retention time of the adjacent C _n and C _{n + 1} peaks of the _n -alkane. Are t ₁ and t ₂ , respectively. When the retention time of the substance X existing between C _n and C _{n + 1} is t _x , the retention index RIx of the substance X is defined by the following equation (1) in the isothermal analysis.
RIx = [(logt _x -logt ₁ ) / (logt ₂ -logt ₁ )] × 100 + 100 × n (1)
Further, in the temperature rising analysis (for example, the temperature rising rate: 20 ° C./min), the retention index RIx of the substance X is defined by the following equation (2).
RIx = [(t _x −t ₁ ) / (t ₂ −t ₁ )] × 100 + 100 × n (2)
A retention index database is obtained by performing GC analysis on various compounds together with n-alkanes to obtain respective retention times, calculating retention indices based on the formula (1) or (2), and collecting the retention indices.

  Next, an embodiment of a gas chromatograph apparatus according to the present invention will be described with reference to FIGS. FIG. 1 is an overall configuration diagram of a gas chromatograph apparatus according to this embodiment.

  A sample vaporizing chamber 2 is provided at the inlet of the column 5 installed in the column oven 4, and a carrier gas is sent into the column 5 through the sample vaporizing chamber 2 from the carrier gas introduction tube 3 at a constant flow rate. When a small amount of liquid sample is injected into the sample vaporizing chamber 2 from the injector 1 at a predetermined timing, the liquid sample is vaporized in a short time and is carried into the column 5 on the carrier gas. The column 5 is maintained at a constant temperature by the column oven 4 (constant temperature analysis), or the temperature rise is controlled according to a predetermined temperature rise program (temperature rise analysis). While passing through the column 5, various compounds contained in the sample are separated in the longitudinal direction of the column 5, and are eluted from the column 5 with a time shift and detected by the detector 6.

  The detection signal of the detector 6 is sent to the data processing unit 10, where a chromatogram is created, and further, predetermined data processing is executed to perform qualitative analysis and quantitative analysis. The control unit 7 achieves the GC analysis operation by controlling the operation of the data processing unit 10 and each of the above units. Connected to the control unit 7 are an input unit 8 for an analyzer to give various instructions and set conditions, and a display unit 9 for displaying analysis results and the like. Many of the functions of the control unit 7 and the data processing unit 10 are realized, for example, by operating a predetermined control / processing program on a personal computer. In addition, as a configuration characteristic of the present embodiment, the data processing unit 10 includes a column deterioration evaluation processing unit 11 and a reference holding index storage unit 12.

  In this apparatus, a predetermined compound A is subjected to GC analysis using a normal column that has not deteriorated, and a retention index of compound A is calculated using a retention index database using n-alkane as a reference substance. The reference holding index storage unit 12 stores the reference holding index RIr. This reference retention index is a reference for evaluating column deterioration. As the compound A, a polycyclic aromatic having a property different from that of the n-alkane in terms of interaction with the column, such as benzene, may be selected.

  In addition, when the compound A is recorded in the retention index database in the same or equivalent column liquid phase as the column used in this apparatus, it is described in the database without performing the actual analysis as described above. The holding index can be used as the reference holding index RIr as it is. In the GC analysis, since the retention index database for a huge number of compounds is published in various public institutions and papers, the labor of analysis can be saved by using such an existing database successfully.

Actually, when the deterioration of the column 5 is evaluated, the process is executed according to the procedure shown in FIG. That is, when the column deterioration evaluation is executed at an arbitrary time point, the GC analysis of the predetermined compound A and the reference substance (n-alkane) is executed under the control of the control unit 7 (step S1). For example, when a sample containing both substances is analyzed, for example, a chromatogram as shown in part of FIG. 3B is obtained. Therefore, the retention time at which peaks of compound A and the reference substance (here, C _n , C _{n + 1} ) appear is obtained, and based on the above formula (1) or (2), the present retention index of compound A RIp is calculated (step S2). The compound A and the reference substance may be subjected to GC analysis separately rather than simultaneously.

  Next, the column deterioration evaluation processing unit 11 calculates a difference ΔRI between the reference holding index RIr held in the reference holding index storage unit 12 and the current holding index RIp previously obtained (step S3), and the difference ΔRI. Is greater than or equal to a preset allowable value (step S4). For example, when the column end is changed by cutting the inlet end of the column 5 or when the analysis conditions such as the column temperature are changed, for example, the chromatogram shown in FIG. The absolute value of the retention time changes to be gram. However, if the properties of the liquid phase of the column do not change, as shown in FIG. 3B, the relative positional relationship of the peak of compound A with respect to the peak of the reference substance is maintained as it is. In that case, the retention index difference ΔRI is a value close to zero. That is, while the column 5 can maintain substantially the same resolution without deterioration, the retention index difference ΔRI is maintained at a value close to zero.

  However, as the deterioration of the column 5 progresses, the interaction of the liquid phase of the column 5 with the reference substance and the compound A changes. For example, as shown in FIG. 3C, the peak of the reference substance on the chromatogram The relative positional relationship of the peak of compound A with respect to changes. In this case, since the retention index of compound A changes, the retention index difference ΔRI is not a value near zero. Since the absolute value of the retention index difference ΔRI increases as the degradation of the column 5 progresses, if it is determined in step S4 that the retention index difference ΔRI is greater than or equal to the allowable value, there is a possibility of column degradation. Judgment is made, and the display unit 9 is displayed as column maintenance recommendation information, for example, to prompt the column inspection (step S5). Here, it is preferable that the allowable value is appropriately determined according to the required resolution, for example, the device manufacturer provides the user with information indicating the relationship between the resolution and the allowable value, and the user refers to this. Alternatively, it may be set appropriately based on experience or experimental values.

  This display allows the analyst to recognize that the deterioration of the column 5 has become severe enough to affect the analysis. For example, the column 5 may be cut at a particularly contaminated portion at the inlet end, or the column 5 itself may be replaced with a new one. Appropriate measures can be taken.

  Actually, the cause of the change in the retention index is not only due to deterioration of the column 5, but also due to, for example, a gas leak in the carrier gas flow path or a malfunction of a device that controls the gas flow rate (for example, a pressure valve or a flow controller). The same can happen when the gas flow rate fluctuates. Therefore, when providing column maintenance recommendation information as described above, it is also preferable to provide information that indicates that there may be some abnormality in the apparatus, such as gas leakage or gas pressure. .

  In the apparatus of the above embodiment, the holding index difference ΔRI and the set allowable value are set so that the analyst can check how much the holding index difference ΔRI exceeds the allowable value (or how low). May be displayed numerically. The retention index is an appropriate parameter for evaluating column degradation, but is difficult for an analyst to understand intuitively. Therefore, instead of displaying the holding index difference ΔRI and the allowable value, this may be converted into the holding time and displayed.

  As described above, in the gas chromatograph apparatus of the present embodiment, the degree of deterioration of the column is evaluated using the retention index. For example, the temperature rising program of the column oven 4 is changed, or a part of the column is changed. Even when the column length is changed by removing the column or other analysis conditions are changed, the degree of deterioration of the column can be evaluated with substantially the same criteria. Therefore, the analyst does not have to worry much about such a difference in analysis conditions and the like, and even in that case, the deterioration of the column can be evaluated with high accuracy.

  It should be noted that the above embodiment is merely an example of the present invention, and it is apparent that modifications and corrections can be made as appropriate within the scope of the present invention. For example, since various detectors can be used in the present invention, for example, the present invention can be applied to a gas chromatograph mass spectrometer combining a gas chromatograph and a mass spectrometer.

BRIEF DESCRIPTION OF THE DRAWINGS The whole block diagram of the gas chromatograph apparatus by one Example of this invention. The flowchart which shows the process sequence at the time of column deterioration evaluation in the gas chromatograph apparatus of a present Example. The wave form diagram for demonstrating the method of column deterioration evaluation in the gas chromatograph apparatus of a present Example. The figure for demonstrating a holding | maintenance parameter | index.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Injector 2 ... Sample vaporization chamber 3 ... Carrier gas introduction tube 4 ... Column oven 5 ... Column 6 ... Detector 7 ... Control part 8 ... Input part 9 ... Display part 10 ... Data processing part 11 ... Column deterioration evaluation processing part 12 ... Reference retention index storage unit

Claims (4)

a) storage means for storing, as a reference holding index, a holding index of a predetermined substance related to a reference substance, which is obtained by gas chromatographic analysis using a normal column;
b) a retention index calculating means for calculating a retention index of the predetermined substance at the present time based on data obtained by performing a gas chromatographic analysis on the predetermined substance and the reference substance by the apparatus;
c) column evaluation means for evaluating the degree of deterioration of the column based on the difference or ratio between the reference holding index stored in the storage means and the current holding index calculated by the holding index calculation means;
d) Information providing means for providing the analyst with information based on the evaluation result by the column evaluation means;
A gas chromatograph apparatus comprising:   The gas chromatograph apparatus according to claim 1, wherein the reference substance is an n-alkane, and the predetermined substance is a substance having a property different from that of the n-alkane with respect to an interaction with a stationary phase of a column.   The gas chromatograph apparatus according to claim 1 or 2, wherein the storage means is an existing retention index database, and the predetermined substance is a substance recorded in the retention index database. The information providing means provides information indicating the possibility of fluctuation in the flow rate of the carrier gas flowing through the column, in addition to information indicating the possibility of a malfunction of the column, based on the evaluation result by the column evaluating means. The gas chromatograph apparatus in any one of Claims 1-3.

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