JP2903454B2 - Chromatogram calculation method - Google Patents

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 configuration of an atmospheric component concentration measuring device using the gas chromatograph (hereinafter, simply referred to as an atmospheric component concentration measuring device). The flow path switching device is composed of, for example, a well-known ten-way valve provided with ten ports (indicated by ten reference numerals a to j in the clockwise direction in the figure). Reference numeral 2 denotes a sample cylinder, one end of which is connected to a port a via a pipe 4 having a three-way solenoid valve 3, and the other end of which is connected to a port a through a three-way solenoid valve 5, and is provided with a driving air introducing filter 6. Connected to mouth 7. Reference numeral 8 denotes a five-way solenoid valve, 9 denotes a ten-way valve diaphragm, and 10 denotes a capillary.

A port b adjacent to the port a is connected to an inlet 13 of the sample S via a tube 11 and a filter 12. Reference numeral 14 denotes a concentration tube connected between the port c adjacent to the port b and the port j adjacent to the port a via the tubes 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. Also, an appropriate filler for concentration is provided in the inside. In some cases, the concentration tube 14 is not provided with a filler for concentration.

[0004] Reference numerals 17 and 18 denote a separation column and an analysis column, respectively. The separation column 17 is connected between ports d adjacent to port c and port h adjacent to one port j via tubes 19 and 20. Connected and 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 composed of, for example, a photoionization detector. The other end of the analyzer 22 is connected to the outlet 23.

A port e adjacent to the port d is connected to a back flash port 25 via a needle valve 24. The port f adjacent to the port e is connected to a carrier gas (for example, N ₂ gas) inlet 30 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 via a pipe 31 to a portion of the pipe 28 between the needle valve 26 and the pressure regulator 26. Reference numeral 32 denotes a pump provided in a pipe 33 which branches off from the pipe 11 and is connected to an air cooling device (not shown) provided in the vicinity of the concentrating pipe 14. Reference numeral 34 denotes a thermostat.

In the case of quantitatively analyzing, for example, benzene, toluene, and xylene in the atmosphere using the apparatus for measuring the concentration of components in the atmosphere having the above structure, the following operation is performed.

[0007] With the ports a to j of the ten-way valve 1 connected as shown by solid lines in the figure, the sample cylinder 2 is operated to suck. As a result, a certain amount of the sample (atmosphere) S is supplied to the sample inlet 13 and the filter 1.
2. It enters the concentration tube 14 via the ports b and c and the tube 15, and further enters the tube 4 via the tube 16 and the ports j and a. At this time, benzene, toluene, and xylene in the sample S are adsorbed in the concentration tube 14.

[0008] The ten-way valve 1 is switched to the state shown by the dotted line in the figure, and the concentrating tube 14 is heated to a predetermined temperature while the carrier gas is introduced from the inlet 30. By this heating, benzene, toluene and xylene adsorbed in the concentration tube 14 are desorbed, and a concentrated sample is obtained. Then, the carrier gas introduced from the inlet 30 enters the concentration tube 14 via the ports i and j and the tube 16,
Further, it enters the separation column 17 via the tube 15, the ports c and d, and the tube 19. By this flow of the carrier gas, benzene, toluene, and xylene in the sample S and components after xylene are substantially separated.

[0009] Benzene, toluene, and xylene separated from the other components further exit the separation column 17 and form a tube 2
0, the ten-way valve 1 is switched to the solid line state in FIG. As a result, benzene, toluene, and xylene that have exited port g are supplied to the needle valve 2
6. Carrier gas passing through ports f and g passes through tube 21 and is further sent to analysis column 18. At the same time, the sample S containing components remaining after xylene remaining in the separation column 17 is supplied to the tube 19, ports d and e by the carrier gas flowing into the separation column 17 via the ports i and h and the tube 20. And is backflushed through the 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 outlet 23.

[0011]

However, benzene,
To obtain the concentrations of toluene and xylene, it is necessary to determine the area of each peak in the chromatogram shown in FIG. 8, but in the conventional chromatogram calculation method,
As shown in FIG. 9A, the peak start time and the peak end time, which are the basis of the area calculation, are calculated for each component.
For example, it is 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 must be set for each component, the number of setting items at the time of calibration becomes very large, and the peak value of the peak is calculated. 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 device, deterioration of the columns 17, 18 and temperature change,
A peak shift may occur in the chromatogram due to a change in the flow rate of the carrier gas or the like. FIG.
(B) shows a peak shift in, for example, benzene. The area in the case where no peak shift occurs is the shaded area R in the figure, whereas the area where the peak shift occurs is indicated by 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 on which the component concentration was calculated could not be correctly obtained, and therefore, it was inevitable that an error would occur in the quantitative results.

The present invention has been made in consideration of the above-mentioned matters, and its object is to eliminate the troublesome setting of the integration time in the integration of the peak area and to reduce the calculation error due to the peak shift as much as possible. It is another object of the present invention to provide a method for calculating a chromatogram.

[0015]

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

[0016]

According to the above-described method for calculating a chromatogram, the integration time is automatically set not only when a predetermined peak is recognized in the chromatogram but also when a predetermined peak is not recognized. In addition, the cumbersome setting of the integration time in the integration of the peak area is eliminated. Then, even if a peak shift occurs, the peak area can be accurately obtained without being affected by the peak shift.

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

[0018]

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

First, in the apparatus shown in FIG. 7, a span gas is introduced from the sample introduction port 13 into the apparatus.
Calibration is performed as shown in the flowchart of FIG. As can be understood from this flowchart, when there is no peak in the component, that is, when there is no rise and fall in the peak, all the processing is performed as an error. Then, only when there are peaks, the area of each peak is calculated. When each component (benzene, toluene, xylene in this case) has a peak as shown in FIG. 4, the peak times A, B, and C of each component are stored. Hereinafter, this peak time (retention time) is referred to as t _n for convenience of explanation.

Next, a case will be described in which, for example, the atmosphere shown in FIG. Figure 3 shows an example of a chromatogram obtained by the measurement, this figure shows the peaks of the obtained such as benzene during calibration, t _n is the peak time for calibration. 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 )]. Then, when there is a peak P in the chromatogram within the set time t _S, chromatogram within the set time t _S
BR> ram slope (rate of change) seeking L _n, the time when equal to or greater than the set value has positive slope L _n of the chromatogram (absolute value increases) as the peak accumulation start time t _nS, negative slope The point in time at which −L _n falls below a certain set value (the absolute value becomes smaller) is defined as the peak integration end time t _nE, and the peak area from the peak integration start time t _nS to the peak integration end time t _nE is determined. .

By doing so, it is not necessary to set the conventional peak start time and peak end time, and the peak area can be automatically obtained. 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 shown by a virtual line (broken line) in FIG. 3, the total area within the set time t _S is obtained. It is. By doing this,
Even when the peak P within 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, not only when there is a remarkable peak within a predetermined set time width t _S , but also when the remarkable peak P does not exist, the peak area is reduced. It can be determined automatically and the component concentration can be obtained.

By the way, in 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 (= have set up dead zone of 2t _f), during the time width t _F is also the slope L _n of the chromatogram becomes below the set value or more or set value,
It is possible not to judge the integration start time or the integration end time, thereby effectively avoiding integration mistakes.

In the above embodiment, benzene, toluene and xylene contained in the atmosphere were quantitatively measured. However, the present invention is not limited to this. Needless to say, the present invention can be applied to the case where the quantification target is single.

[0027]

As described above, according to the present invention,
In addition to the case where a predetermined peak is recognized in the chromatogram obtained in the actual measurement, as well as the case where the predetermined peak is not recognized, the integration time is automatically set. The cumbersome setting of the integration time in is eliminated. 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 even a component having an isomer can be obtained. And the peak area can be accurately obtained.

Therefore, according to the present invention, quantitative analysis of components can be accurately performed, for example, when measuring the concentration of components in the atmosphere using a gas chromatograph.

[Brief description of the drawings]

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

FIG. 2 is a flowchart illustrating an example of an operation procedure when performing calibration using a span gas for performing 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 peak times of respective components in a chromatogram obtained at the time of 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 certain component of 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.

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

[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 : slope of chromatogram, t _F : dead band.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01N 30/86

Claims (2)

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