JP4507962B2 - Gas chromatograph - Google Patents

Description

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

  In general, in gas chromatographic analysis, in order to identify a peak appearing in a chromatogram, a retention time (retention time) that is a time required for a compound to pass through a column is used. However, the retention time is not a value intrinsic to the compound, but is a value that varies depending on various analysis conditions such as the carrier gas flow rate, the column temperature, the column size, and the column liquid phase thickness. Therefore, unless these various analysis conditions are the same, the peak identification using the retention time cannot be performed accurately. Therefore, for example, a retention time is obtained in advance by analyzing a sample of the analysis target compound under a desired analysis condition, and the sample containing the analysis target compound is analyzed under the desired analysis condition using the retention time. Data processing such as identifying peaks appearing in the chromatogram obtained by analyzing in step (b) is performed.

  However, in order to perform such peak identification, it is necessary to prepare preparations for all the compounds to be analyzed and analyze them in advance. If there are many compounds to be analyzed, preparation is troublesome and takes time and effort. .

  On the other hand, unlike the above-described holding time, a holding index (retention index) has been conventionally used as a parameter that does not depend on analysis conditions or instrument differences (see, for example, Patent Document 1). The retention index in the 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, based on the appearance position of the methane (CH ₄ ) peak in the chromatogram shown in FIG. 10, the retention times of the adjacent C _n and C _{n + 1} peaks of the _n -alkane are t ₁ and t ₂ , respectively. To do. 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.

  When using this retention index database to identify peaks of unknown compounds appearing in chromatograms, the retention index has little dependency on the instrument and analysis conditions, so there is no need to worry about these factors. There is. However, on the other hand, the reference substance (n-alkane in the above example) is analyzed together with the analysis target compound under the same conditions to determine the retention time of the reference substance, and the retention time of the reference substance and the retention index of the analysis target compound From this, it is necessary to estimate the retention time of the analysis target compound. Therefore, it is necessary to prepare a reference material standard, and it is necessary to perform a gas chromatographic analysis of the reference material standard at least once.

JP-A-11-201960

  As described above, in the peak identification method in the conventional gas chromatograph apparatus, it is necessary to analyze a predetermined standard such as a standard of a target compound to be analyzed and a standard of a reference material, and it is troublesome to prepare such standard. . Moreover, even if there was a sample that was not an analysis target compound or a reference material, such a sample could not be used.

  The present invention has been made in view of the above problems, and the object of the present invention is to eliminate the need to prepare and analyze the preparation of the analysis target compound and the reference substance of the retention index. It is an object of the present invention to provide a gas chromatograph apparatus that can reduce the troublesomeness of aligning and the labor of analysts.

Gas chromatograph according to the present invention was made in order to solve the above SL problem,
a) an analysis execution means for performing a gas chromatographic analysis on a plurality of compounds having a known retention index based on a predetermined reference substance and obtaining a retention time of each compound;
b) first retention time estimation means for estimating the retention time of the reference substance based on the relationship between the retention times of the plurality of compounds and the known retention index of each substance;
c) second retention time estimation means for estimating the retention time of the analyte compound from the retention time of the reference substance obtained by the first retention time estimation means and the known retention index of the analyte compound;
d) an identification processing means for identifying a peak appearing in a chromatogram created by gas chromatographic analysis of a sample containing the analysis target compound using the retention time estimated by the second retention time estimation means;
It is characterized by having.

Here, examples of the reference substance include n-alkanes, polycyclic aromatics, and fatty acids derivatized with PFB-Br (pentafluorobenzyl bromide) .

The gas chromatograph apparatus according to the present invention is obtained by gas chromatographic analysis of a compound that is not an analysis target (of course, may be an analysis target) with a known retention index based on a predetermined reference substance. time and holding of the compound, based on the relationship between the retention indices of the compounds, the retention index is that to estimate the retention time of the different compounds are known. "Another compound" of that is a reference material, you estimate the retention time of the analytes after temporarily determined retention time of the reference material from the estimated value of the retention time.

Therefore, Oite gas chromatograph equipment according to the present invention, the analysis rather than the preparation of the subject compounds or reference substance, retention index at hand is by performing an analysis of a preparation of any compound which is known, analysis Information necessary for identifying the target compound can be obtained. As a result, it is not necessary to prepare the analysis target compound or the reference material and analyze it, thereby improving the efficiency and cost of the analysis work.

[ Reference Example 1]
Before explaining an embodiment of a gas chromatograph apparatus according to the present invention, reference example relating 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 reference example.

  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.

As a characteristic configuration of the present reference example, the data processing unit 10 includes a retention index database 13, a retention time estimation unit 12, and a peak identification processing unit 11. In the retention index database 13, as an example, retention indices of various compounds using n-alkane as a reference substance are recorded corresponding to the compound names. Of course, a retention index database in which the reference substance is another compound such as polycyclic aromatic benzene may be used.

Next, characteristic peak identification processing in the gas chromatograph apparatus of this reference example will be described with reference to the flowchart of FIG. 2 and FIGS. 3 and 4.

First, under the control of the control unit 7, predetermined analysis conditions (here, arbitrary two kinds of compounds α and β having a known retention index based on n-alkane recorded in the retention index database 13 are known. In this case, the GC analysis is executed. By this analysis, a chromatogram as shown in FIG. 3 is acquired, and the retention time estimation unit 12 obtains retention times (RT) a and b of the respective compounds α and β (step S1). Since the retention index (RI) of the compounds α and β is given from the retention index database 13, combinations (RT, RI) of the retention time (RT) and the retention index (RI) are (a, A), (b, B).

  When plotting (RT, RI) of the compounds α and β on the graph with the retention index (RI) on the horizontal axis and the retention time (RT) on the vertical axis, points Pa and Pb in FIG. As shown in Therefore, a line passing through these two points Pa and Pb is drawn. In FIG. 4, a line for linearly interpolating the two points Pa and Pb is drawn. The line drawn here represents the relationship between the retention index and the retention time under the above analysis conditions, and represents a conversion formula from the retention index to the retention time.

Therefore, the holding time estimation unit 12 creates and holds the following equation (3) as a conversion equation from the holding index (RI) to the holding time (RT) (step S3).
RT = [(ba) / (BA)] * (RI-A) + a (3)
Note that the holding time can be calculated by extrapolating the straight line determined by the expression (3) in a range other than the section between A and B. Then, the retention time estimation unit 12 estimates the retention time for each compound whose retention index is known and whose retention time is unknown from the retention index database 13 based on the above conversion formula. The peak identification processing unit 11 identifies the peak on the chromatogram obtained by the GC analysis for the unknown sample, using the estimated retention time given from the retention time estimation unit 12 (step S4).

For example, when the retention indices of the analysis target compounds Un ₁ and Un ₂ are RI ₁ and RI ₂ , the retention times RT ₁ and RT ₂ are obtained from the equation (3), respectively (see FIG. 4), and this retention time is the central value. RT ₁ ± Δt and RT ₂ ± Δt having a margin of a predetermined time width are set as the peak identification windows of the analysis target compounds Un ₁ and Un ₂ . Then, when there are peaks in the two windows in the chromatogram obtained by GC analysis of the unknown sample, for example, as shown by the dotted line in FIG. 3, these are analyzed compounds Un ₁ and Un ₂ , respectively. Is identified as a peak. For all compounds for which the retention index is known, that is, recorded in the retention index database 13, the retention time can be estimated as described above, and peak identification can be performed accordingly.

[Modification of the above reference example]
The gas chromatograph apparatus according to the above Reference Example, two compounds alpha, created a conversion formula between retention index and the retention time as a result of analyzing the using (3) for β, but the compound to be analyzed The accuracy of the conversion formula can be increased by increasing the number of types. For example, when GC analysis is performed on four types of compounds α, β, γ, and δ whose retention indices are known, and a chromatogram as shown in FIG. 5 is obtained, retention time (RT) and retention index (RI) The combinations (RT, RI) are (a, A), (b, B), (c, C), and (d, D).

When the (RT, RI) based on the above analysis results for these four types of compounds α, β, γ, and δ are plotted on a graph with the horizontal axis representing the retention index and the vertical axis representing the retention time, point Pa in FIG. , Pb, Pc, Pd. Therefore, a line that linearly interpolates between two adjacent points is drawn, and a conversion formula representing this line is created.
Then, in the A to B section,
RT = [(ba) / (BA)] * (RI-A) + a (4)
In the B-C section,
RT = [(c−b) / (C−B)] × (RI−B) + b (5)
In section C to D,
RT = [(dc) / (DC)] * (RI-C) + c (6)
And the conversion formula is obtained. In the section below A, the line determined by equation (4) is extrapolated outside the point Pa, and in the section above D, the line determined by equation (6) is extrapolated as it is outside the point Pd.

According to the above conversion formula, the accuracy of estimating the retention time from the retention index is improved as compared with the case of the above reference example, so that the accuracy of peak identification can be improved, and erroneous identification or oversight of peaks can be reduced. . Of course, instead of the conversion formula obtained by performing the linear interpolation as described above, the coefficient may be calculated on the assumption that the nth order polynomial passes through each point, and this polynomial may be used as the conversion formula.

[ Example]
In the above reference example, the retention times of any of a plurality of compounds recorded in the retention index database 13 were measured, and the retention time of the compound to be analyzed was estimated from the relationship between the retention times and the retention indices. However, in the examples according to the present invention, the retention time of the n-alkane which is the reference substance of the retention index is estimated, and the retention time is estimated from the retention time of the n-alkane and the retention index of the analysis target compound. The For gas chromatograph apparatus according to the embodiment performs such processing operations, it will be described.

The basic configuration of a gas chromatograph apparatus according to this embodiment is the same as the reference example, description of the structure since the peak identification processing method in the data processing unit 10 is different only omitted.

First, under the control of the control unit 7, predetermined analysis conditions (here, three compounds α, β, and γ, which are recorded in the retention index database and whose retention indices based on n-alkanes are known, are described. The GC analysis is executed with the temperature rising analysis). Here, as the compounds α, β, and γ, those that satisfy the following conditions are selected for the _n -alkanes C _n , C _{n + 1} , and C _{n + 2} that are the reference materials for the retention index.
C _n <RI (α), RI (β) <C _{n + 1} where RI (α) ≠ RI (β)
C _{n + 1} <RI (γ) <C _{n + 2}
By the above analysis, a chromatogram as shown in FIG. 7 is obtained, and retention times (RT) a, b, and c of the respective compounds α, β, and γ are obtained. The combinations (RT, RI) of the retention times (RT) and retention indices (RI) of the compounds α, β, γ are (a, A), (b, B), (c, C).

Next, the retention times of C _n and C _{n + 1} are estimated from the retention times and retention indices of the compounds α and β, that is, (a, A) and (b, B). In temperature rising analysis, from equation (2):
RI = {[RT−RT (C _n )] / [RT (C _{n + 1} ) −RT (C _n )]} × 100 + 100 × n (7)
And when this is transformed,
(RI-100 × n) × RT (C n + 1) + (100 × n + 100-RI) × RT (C n) = RT ... (8)
It becomes. By substituting RI and RT of the compounds α and β into the equation (8) and solving the equation, RT (C _n ) and RT (C _{n + 1} ) are obtained.

Further, the retention times of C _{n + 1} and C _{n + 2} can be obtained by the same equation as the equation (8), and the retention time and retention index of compound γ are known, and the retention time RT of C _{n + 1} is known from the above calculation. Since (C _{n + 1} ) is also obtained, the retention time of C _{n + 2} is obtained by substituting these into the equation. Furthermore, when the retention time of n + alkane of n + 3 or more is required, the retention time can be estimated by repeating the same process as described above.

Thereafter, from the n-alkane retention time estimated as described above and the retention index of the analysis target compound, the retention time of the analysis target compound can be estimated by the equation (8). When the retention time of the analysis target compound is obtained, the peak appearing in the chromatograph obtained by chromatographic analysis of the sample is identified using this as in the above Reference Example . This makes it possible to identify any analysis target compound as in the reference example .

[Modification Example]
Or it may be as follows as a data processing according to the modification of the gas chromatograph apparatus according to the aforementioned embodiments. That is, under the control of the control unit 7, predetermined analysis conditions (here, three compounds α, β, and γ, which are recorded in the retention index database and whose retention index based on n-alkane is known, are described here. In this case, the GC analysis is executed. Here, as the compounds α, β, and γ, those satisfying the following conditions are selected with respect to the _n -alkanes C _n and C _{n + 1} that are the reference materials of the retention index.
RI (α) <C _n <RI (β)
C _{n + 1} <RI (γ) <C _{n + 2}
By the above analysis, a chromatogram as shown in FIG. 8 is obtained, and the combination (a, A) of the retention time (RT) and retention index (RI) of the compounds α, β, γ as in Example 2 above. , (B, B), (c, C) are acquired.

Next, the retention times of C _n and C _{n + 1} are estimated from the retention times and retention indices of the compounds α and β, that is, (a, A) and (b, B). C _n retention time RT _{(C n)} is represented by the following equation (9).
RT (C _n ) = [(b−a) / (BA)] × [RI (C _n ) −A] + a (9)
That is, the equation (9) is obtained by linearly interpolating two points (a, A) and (b, B) in a graph in which the horizontal axis is the holding index and the vertical axis is the holding time as shown in FIG. This is the expression that represents the line. Similarly, the holding time of C _{n + 1} can be obtained. Thereafter is the same as the above embodiment.

In the temperature rising analysis, since the entropy per methylene unit is substantially equal, the retention time of one methylene unit interval is substantially equal. Therefore, for example, even when a plurality of n-alkanes C _n , C _{n + 1} ,... Are included between the retention index A of the compound α and the retention index B of the compound β, these C _n , C _{n + 1} ,. It is possible.

As in the reference example, since the relationship between the retention time and the retention index becomes almost linear during the temperature rise analysis, the accuracy of the estimated value using a conversion equation such as the equation (9) is improved. high. On the other hand, in the case of constant temperature analysis instead of temperature rise analysis, a shift of logarithm log occurs as can be seen from comparison between the equations (1) and (2). However, since the difference is not so large depending on the analysis conditions, the above-mentioned conversion may be applicable even in the constant temperature analysis.

  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. In the case of a gas chromatograph mass spectrometer, the peaks appearing in the total ion chromatogram and the mass chromatogram focusing on a specific mass number are identified based on the retention time, and the peaks appearing in the mass spectrum are also identified. In some cases, a process for finally identifying the correct component is performed together with the identification results, but it is easy to apply the data processing as in the present invention to achieve the same effect even in such a process. I can think of it.

The whole block diagram of the gas chromatograph apparatus by the reference example of this invention. The flowchart of the peak identification process in the gas chromatograph apparatus of a reference example . Explanatory drawing of the peak identification process operation | movement in the gas chromatograph apparatus of a reference example . Explanatory drawing of the peak identification process operation | movement in the gas chromatograph apparatus of a reference example . Explanatory drawing of the peak identification processing operation in the gas chromatograph apparatus by the modification of a reference example . Explanatory drawing of the peak identification processing operation in the gas chromatograph apparatus by the modification of a reference example . Illustration of peak identification process operation in a gas chromatograph apparatus according to the embodiment of the present invention. Explanatory drawing of the peak identification process operation | movement in the gas chromatograph apparatus by the modification of an Example. Explanatory drawing of the peak identification process operation | movement in the gas chromatograph apparatus by the modification of an Example. Explanatory drawing about 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 ... Peak identification process part 12 ... Holding time estimation unit 13 ... holding index database

Claims (2)

a) an analysis execution means for performing a gas chromatographic analysis on a plurality of compounds having a known retention index based on a predetermined reference substance and obtaining a retention time of each compound;
b) first retention time estimation means for estimating the retention time of the reference substance based on the relationship between the retention times of the plurality of compounds and the known retention index of each substance;
c) second retention time estimation means for estimating the retention time of the analyte compound from the retention time of the reference substance obtained by the first retention time estimation means and the known retention index of the analyte compound;
d) an identification processing means for identifying a peak appearing in a chromatogram created by gas chromatographic analysis of a sample containing the analysis target compound using the retention time estimated by the second retention time estimation means;
A gas chromatograph apparatus comprising: The gas chromatograph according to claim 1, wherein the reference substance is a fatty acid derivatized with n-alkane, polycyclic aromatic, or PFB-Br (pentafluorobenzyl bromide) .

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