JPH0783904A - Chromatogram operation method - Google Patents

Abstract

PURPOSE:To provide a chromatogram operation method where the trouble for setting an integration time when operating a peak area is eliminated and at the same time the operation error due to peak shift is reduced as much as possible. CONSTITUTION:A peak time tn of a target constituent to be measured in chromatogram is obtained on calibration and a time width which is equal to an allowable tailing time tnT before and after the peak time tn is set on measurement. When rising n and trailing in a peak P of chromatogram is located within the setting time width ts. an area from the time when a positive inclination Ln of chromatogram is equal to or more than a set value before the peak time tn to the time when a negative inclination -Ln, of chromatogram is equal to or less than a set value after the peak time t is obtained. When there are no rising and trailing in the peak P of chromatogram within the setting time width ts, the area within the setting time width ts is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for calculating a chromatogram in an atmospheric component concentration measuring apparatus using a gas chromatograph capable of measuring specific components such as benzene, toluene and xylene contained in the atmosphere. .

[0002]

2. Description of the Related Art FIG. 7 is a diagram showing a general structure of an atmospheric component concentration measuring apparatus using the above-mentioned gas chromatograph (hereinafter, simply referred to as an atmospheric component concentration measuring apparatus). The flow path switching device is composed of a well-known ten-way valve having, for example, 10 ports (indicated by 10 symbols a to j provided in the clockwise direction in the drawing). Reference numeral 2 is a sample cylinder, one end of which is connected to the port a through a pipe 4 having a three-way solenoid valve 3 and the other end of which is provided with a filter 6 through a three-way solenoid valve 5. It is connected to the mouth 7. In addition, 8 is a five-way solenoid valve, 9 is a ten-way valve diaphragm, and 10 is a capillary.

A port b adjacent to the port a is connected to an inlet 13 for the sample S via a tube 11 and a filter 12. Reference numeral 14 is a concentrating pipe connected between a port c adjacent to the port b and a port j adjacent to the port a via pipes 15 and 16. Although not shown in detail, the concentrating tube 14 is configured to generate heat when energized by itself and to raise the temperature. In addition, an appropriate concentration filler is provided inside thereof. Note that the concentration tube 14 may not be provided with a concentration filler.

Reference numerals 17 and 18 denote a separation column and an analysis column, respectively. The separation column 17 is provided with pipes 19 and 20 between a port d adjacent to the port c and a port h adjacent to one port j. Connected, analytical column 18
Has one end connected to a port g adjacent to the port h via a tube 21, and the other end connected to an analysis unit 22 including, for example, a photoionization detector. The other end of the analysis unit 22 is connected to the outlet 23.

The port e adjacent to the port d is connected to the back flush port 25 via the needle valve 24. A port f adjacent to the port e is connected to an inlet 30 for a carrier gas (for example, N ₂ gas) having a filter 29 via a pipe 28 having a needle valve 26 and a pressure regulator 27. The port i adjacent to the port h is connected to the portion of the pipe 28 between the needle valve 26 and the pressure regulator 26 via the pipe 31. In addition, 32 is a pump provided in a pipe 33 branched from the pipe 11 and connected to an air cooling device (not shown) provided in the vicinity of the concentration pipe 14, and 34 is a constant temperature bath.

When quantitatively analyzing benzene, toluene, and xylene in the atmosphere using the atmospheric component concentration measuring apparatus having the above-described structure, the following operation is performed.

The sample cylinder 2 is suctioned while the ports a to j of the ten-way valve 1 are connected as shown by the solid lines in the figure. As a result, a certain amount of sample (atmosphere) S is transferred to the sample inlet 13 and the filter 1.
2, the ports b and c, and the pipe 15 to enter the concentrating pipe 14, and the pipe 16 and the ports j and a to enter the pipe 4. At this time, benzene, toluene, and xylene in the sample S are adsorbed in the concentration tube 14.

The ten-way valve 1 is switched to the state shown by the dotted line in the figure, and the carrier gas is introduced from the inlet 30 and, at the same time, the concentrating tube 14 is heated to a predetermined temperature. By this heating, benzene, toluene, and xylene adsorbed in the concentrating tube 14 are desorbed to obtain a concentrated sample. Then, the carrier gas introduced from the inlet 30 enters the concentrating pipe 14 through the ports i, j and the pipe 16,
Further, it enters the separation column 17 through the pipe 15, the ports c and d, and the pipe 19. By the flow of the carrier gas, benzene, toluene, and xylene in the sample S are almost separated from the components after xylene.

The benzene, toluene, and xylene separated from the other components further leave the separation column 17, and the pipe 2
At the time of passing 0, ports h, g, the ten-way valve 1 is switched to the solid line state in the figure. As a result, the benzene, toluene, and xylene exiting the port g will be removed by the needle valve 2
The carrier gas having passed through the ports 6, f and g passes through the pipe 21 and is further sent to the analysis column 18. At the same time, the sample S containing the components after xylene remaining in the separation column 17 is supplied to the tubes 19, ports d, e by the carrier gas flowing into the separation column 17 through the ports i, h and the tube 20. And backflush via needle valve 24.

Benzene sent to the analytical column 18,
Toluene and xylene are further introduced into the analysis unit 22,
For example, a chromatogram as shown in FIG. 8 is obtained. In this figure, B, T and X represent benzene, toluene and xylene, respectively. The benzene, toluene, and xylene after the analysis are discharged from the discharge port 23.

[0011]

By the way, benzene,
In order to obtain the concentrations of toluene and xylene, it is necessary to find the area of each peak in the chromatogram shown in FIG. 8, but in the conventional chromatogram calculation method,
As shown in FIG. 9 (A), the peak start time and the peak end time, which are the basis of the area calculation, are calculated as follows.
For example, it has been set for each of benzene (X), toluene (T), and xylene (X). This Figure 9
In (A), A, C and E are peak start times,
B, D, and F indicate peak end times, respectively.

However, in the above-described conventional chromatogram calculation method, since the peak start time and the peak end time have to be set for each component, the number of setting items at the time of calibration becomes very large, and the peak In addition to the inconvenience that automatic determination is difficult, there are the following problems.

That is, in this type of atmospheric component concentration measuring apparatus, deterioration of the columns 17 and 18, temperature change,
A peak shift may occur in the chromatogram due to a change in the flow rate of the carrier gas. Figure 9
(B) shows the peak shift in benzene, for example, and the area when no peak shift occurs is the shaded area R in the figure, whereas when peak shift occurs, the area is the shaded area. R '. This is because the peak start time shifts from A to A'and the peak end time shifts from B to B'with the peak shift. As a result, the peak area, which is the basis for the component concentration calculation, could not be obtained correctly, so that it was unavoidable that an error occurred in the quantitative result.

The present invention has been made in consideration of the above matters, and an object thereof is to eliminate the trouble of setting the integration time in the integration of peak areas and to minimize the calculation error due to the peak shift. Another object of the present invention is to provide a chromatogram calculation method.

[0015]

In order to achieve the above object, the method of computing a chromatogram of the present invention obtains the peak time of a component to be measured in a chromatogram during calibration, and at the time of measurement, before and after the peak time, respectively. If a time width equal to the allowable tailing time is set and there is a rise and fall at the peak of the chromatogram within this set time width, the positive slope of the chromatogram will be above the set value before the peak time. After the peak time, the area from the time when the negative slope of the chromatogram becomes equal to or less than the set value is obtained, and when there is no rise and fall at the peak of the chromatogram within the set time width, The area within the set time width is calculated.

[0016]

According to the above chromatogram calculation method, not only when a predetermined peak is recognized in the chromatogram but also when the predetermined peak is not recognized, the integration time is automatically set. Therefore, the trouble of setting the integration time for integrating the peak areas is eliminated. Then, even if the peak shift occurs, the peak area can be accurately obtained without being affected by the influence.

In particular, when a predetermined peak is recognized in the chromatogram, a dead zone having a predetermined time width may be set before and after the peak time at the time of calibration. By doing so, even if there is a valley portion based on an isomer in the peak as shown in the chromatogram, for example, as shown in FIG. 6, that portion should not be the integration start time point or the integration end time point. As a result, the peak area can be accurately obtained.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

First, in the apparatus shown in FIG. 7, the span gas is introduced into the apparatus through the sample inlet 13.
Calibration is performed as shown in the flowchart of FIG. As can be seen from this flowchart, when there is no peak in the component, that is, when there is no rising or falling in the peak, all processing is performed as an error. Then, the area of each peak is measured only when there is a peak. If each component (in this case, benzene, toluene, xylene) has a peak as shown in FIG. 4, the peak times A, B, C of each component are stored. Hereinafter, for convenience of explanation, this peak time (retention time) is referred to as t _n .

Next, a case will be described in which, for example, the atmosphere shown in FIG. 7 is introduced as sample S into the sample introduction port 13 for measurement. FIG. 3 shows an example of a chromatogram obtained by this measurement. This figure shows, for example, a benzene peak obtained at the time of calibration, and t _n is a peak time at the time of calibration. Further, P indicates a peak (actual peak) obtained at the time of measurement.

In the present invention, upon calibration of the peak, respectively permissible tailing time t _nT equal duration before and after the time t _n, that is, setting a time width 2t _nT around the peak time t _n during calibration [Hereinafter, this time is referred to as a set time width t _S (= 2t _nT )]. When the chromatogram within the set time t _S has a peak P, the slope (rate of change) L _n of the chromatogram within the set time t _S is calculated, and the set value with the positive slope L _n of the chromatogram is set. The time point above (the absolute value increases) is defined as the peak integration start time point t _nS , and the negative slope −
The time when L _n is below a certain set value (the absolute value becomes small) is set as the peak integration end time t _nE, and the peak area from these peak integration start time t _nS to the peak integration end time t _nE is obtained.

By doing so, it becomes unnecessary to set the conventional peak start time and peak end time, the peak area can be automatically obtained, and as shown in FIG. even if t _n peak shift as shifted in t _n ', without being affected, it is possible to obtain the peak area accurately.

When there is no remarkable peak P in the chromatogram within the set time width t _S as indicated by a virtual line (broken line) in FIG. 3, the total area within the set time t _S is obtained. Of. By doing this,
Even if the peak P in the set time width t _S is low, the peak area can be automatically obtained.

FIG. 1 shows an example of a flowchart showing the above operation. As can be understood from this figure, according to the method of the present invention, the peak area can be calculated not only when the remarkable peak exists within the predetermined set time width t _S but also when the remarkable peak P does not exist. It can be automatically determined, and the component concentration can be obtained.

By the way, in the case of a component having an isomer such as xylene, the peak P is cut off halfway as shown in FIG. In such a case, the portion indicated by x may be determined as the integration start time or the integration end time. In order to eliminate such errors, at the time when the prominent peak P exists within the predetermined set time width t _S is around the peak time t _n during calibration, a predetermined time width t _F (= 2t _f ) dead zone is set, and during this time width t _F , even if the slope L _{n of the} chromatogram becomes equal to or more than the set value or less than the set value,
It is possible not to judge the time point as the integration start time point or the integration end time point, whereby the integration error can be effectively avoided.

In the above-mentioned embodiment, benzene, toluene and xylene contained in the atmosphere were quantitatively measured. However, the present invention is not limited to this, and simultaneous quantification of a plurality of other components is possible. It goes without saying that the present invention can be applied to the case where a single quantitative object is used.

[0027]

As described above, according to the present invention,
Not only when the specified peak is observed in the chromatogram obtained in actual measurement, but also when the specified peak is not recognized, the integration time is automatically set. There is no need to worry about setting the integration time in. And even if a peak shift occurs,
The peak area can be accurately obtained without being affected by the influence.

In particular, when a predetermined peak is recognized in the chromatogram, a dead band having a predetermined time width is set before and after the peak time at the time of calibration, so that a component having an isomer is also detected. , The peak area can be obtained with high accuracy.

Therefore, according to the present invention, the quantitative analysis of the components can be performed with high accuracy, for example, when the concentration of the components in the atmosphere is measured by using a gas chromatograph.

[Brief description of drawings]

FIG. 1 is a flowchart showing an example of an operation procedure at the time of measurement for carrying out the chromatogram calculation method of the present invention.

FIG. 2 is a flowchart showing an example of an operation procedure when performing calibration using a span gas for carrying out the chromatogram calculation method of the present invention.

FIG. 3 is a diagram showing an example of a chromatogram obtained by measurement.

FIG. 4 is a diagram showing the peak time of each component in a chromatogram obtained during calibration.

FIG. 5 is a diagram for explaining the operation of the present invention.

FIG. 6 is a diagram showing an example of a chromatogram of a component having an isomer.

FIG. 7 is a configuration diagram showing an example of an apparatus to which the method of the present invention is applied.

FIG. 8 is a diagram showing an example of a chromatogram containing benzene, toluene, and xylene.

9A and 9B are diagrams for explaining a conventional chromatogram calculation method and its drawbacks.

[Explanation of symbols]

P ... peak, t _n ... peak time at the time of calibration, t _nT ... acceptable tailing time, t _S ... set time width, L
_n ... chromatogram slope, t _F ... dead band.

Claims (2)

[Claims] 1. A peak time of a component to be measured in a chromatogram is obtained at the time of calibration, and a time width equal to an allowable tailing time is set before and after the peak time at the time of measurement, and the chromatogram of the chromatogram is set within the set time width. When there is a rising edge and a falling edge at the peak, the negative slope of the chromatogram after the peak time becomes less than the set value from the time when the positive slope of the chromatogram becomes more than the set value before the peak time. The chromatogram calculation method is characterized in that the area up to is set, and when there is no rising or falling at the peak of the chromatogram within the set time width, the area within the set time width is found. . 2. The dead band of a predetermined time width is set before and after the peak time of the calibration when there is a rise and a fall at the peak of the chromatogram within the set time width. Chromatogram calculation method.