JPH0783907A - Channel switching method - Google Patents

Abstract

PURPOSE:To compensate the deviation of retention time due to the deterioration, etc., of a column by obtaining the ratio between the retention time of a measurement target constituent first reaching an analysis part and that when the measurement target constituent last reaching the analysis part cannot be unloaded and than automatically adjusting the timing of unloading. CONSTITUTION:The ratio of retention times tA, tB, and tC of constituents to be measured in air, namely benzene A, toluene B, and xylene C, is always constant. Then, when a non-measurement target constituent appearing later than the latest xylene C is not introduced to an analysis part 22 and an optimum switching time tP of a + way valve 1 where xylene C is not back-flashed (unloaded) is obtained, the ratio between the time tP and the retention time tA of benzine A first reaching the analysis part is also always constant. Therefore, a ratio tP/tA) between the unloading time (switching of the valve 1) time tP using columns 17 and 18 and the retention time tA of benzine A is stored in advance and the retention time tA of the detected benzine A is operated by the valve 1, thus compensating the deviation of the retention time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flow path switching method 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. 2 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). In FIG. 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.

17 and 18 are separation columns (hereinafter,
The second column 17 includes a pipe 19 between a port d adjacent to the port c and a port h adjacent to the port j. Is connected via the first 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 27 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.

[0006] When the benzene, toluene, and xylene in the atmosphere are quantitatively analyzed by distinguishing them from the components after the xylene by using the atmospheric component concentration measuring apparatus having the above-mentioned configuration, 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. That is, as shown in FIG. 3 (A), the first column 18 connected to the analysis unit 22 is connected to the second column 17 via the ten-way valve 1. In this state, the carrier gas is introduced through 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 via the ports i and j and the pipe 16, and further enters the second column 17 via the pipe 15, 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 are further discharged from the second column 17 into 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. That is, as shown in FIG. 3B, the first column 18 connected to the analysis unit 22.
Are separated from the second column 17. by this,
The benzene, toluene, and xylene exiting the port g pass through the pipe 21 by the carrier gas passing through the needle valve 26 and the ports f and g, and are further sent to the first column 18. At this time, the first column 18 and the second column 17 are as shown in FIG. 4 (A), for example. In this figure, A, B and C represent benzene, toluene and xylene, respectively.

The benzene A, toluene B, and xylene C sent to the first column 18 are further introduced into the analysis unit 22, and the earliest benzene A is stored in the detection unit 22 as shown in FIG. 4B. Reached and toluene B and xylene C were first
The other components remain in the column 18 and the second column 17.

Further, in the first column 18, the benzene A, toluene B, and xylene C are finely separated, and as shown in FIG.
Reaches the detection unit 22 and reaches its retention time. At this time, xylene C is in the first column 18. At this time, the sample S containing the components after the xylene remaining in the second column 17 is the ports i, h and the tube 20.
The carrier gas flowing into the second column 17 via the back column is backflushed through the tube 19, the ports d and e and the needle valve 24.

[0012]

By the way, when a plurality of measurement target components are separated from other non-measurement target components and quantitative analysis is performed, the component of the measurement target components that reaches the detection unit 22 latest (as described above). In this example, the retention time of xylene) occupies a very important position. That is, the xylene retention time may shift due to deterioration of the columns 17 and 18 or flow rate change, but if the retention time shifts, the following problems occur.

That is, when the concentration is measured by a chromatogram, the timing of switching the flow path by the ten-way valve 1, that is, the timing of backflushing is an important point for shortening the measurement sequence time. This timing is related to the retention time shift of xylene, and if this timing is too long, there is the inconvenience that the non-measurement target component that appears after the latest xylene will interfere with the next measurement sequence. Further, if it is too short, there is a disadvantage that xylene, which is a component to be measured, is also backflushed.

The present invention has been made in consideration of the above matters, and an object thereof is to switch the flow paths even if the retention time of the component which reaches the detection section latest among the components to be measured deviates. It is an object of the present invention to provide a flow path switching method capable of automatically correcting the backflush timing by the device.

[0015]

In order to achieve the above-mentioned object, the flow path switching method of the present invention provides a retention time of a measurement target component which reaches the analysis section earliest among a plurality of measurement target components, and a plurality of measurements. Of the target components, the ratio of the time when the measurement target component that reaches the analysis unit latest is not backflushed is obtained, and during calibration, the retention time of the measurement target component that reaches the analysis unit earliest among the multiple measurement target components and , The ratio is used to adjust the backflush timing.

[0016]

According to the flow path switching method described above, the backflush timing is automatically optimized even if the retention time of the measurement target component that arrives at the analysis unit latest is deviated due to column deterioration or flow rate change. Can be adjusted to be

[0017]

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

First, FIG. 1 shows benzene A, toluene B,
The chromatogram containing each peak of xylene C is shown. Then, in FIG. 1, t _A , t _B , t
_C indicates the retention times of benzene A, toluene B, and xylene C, respectively. It is known that these retention times have the following relationships. That is, in this case, the ratio of the retention times t _B and t _C of toluene B and xylene C to the retention time t _A of benzene A, which is the earliest component to be measured, is always constant. That is, t _B / t _A = const t _C / t _A = const.

Next, the inventors changed the flow path switching timing by the ten-way valve 1 variously so that the non-measurement target component appearing after xylene was not introduced into the analysis section 22 and the xylene was backed up. The conditions under which the flash did not occur were determined by trial and error. If such an optimum timing is defined as the switching time t _D of the ten-way valve 1, the ratio between this time t _D and the retention time t _{A of} benzene which reaches the analysis unit 22 first is always constant, that is, , T _D / t _A = const.

Therefore, in the present invention, in the apparatus shown in FIG. 2, the ratio (= t _D / t _{A of the} backflush time t _D and the retention time t _{A of} benzene A when columns 17 and 18 are used. ) Is obtained in advance and stored in memory. Next, at the time of calibration, the retention time t _A of the benzene _A is read as the switching timing of the ten-way valve 1. Then, the ratio and the retention time t _{A of} benzene A obtained at the time of calibration
Thus, the switching timing (backflush time t _D ) of the ten-way valve 1 at the time of measurement is set.

Therefore, even if the retention time t _{C of} xylene C deviates due to deterioration of the columns 17 and 18 or flow rate change, the switching timing of the ten-way valve 1 is automatically adjusted so as to always be an appropriate value for each calibration. Can be adjusted to

Needless to say, the present invention is not limited to the above-mentioned embodiments, but can be applied to quantitative analysis of other plural components to be measured. Further, instead of the Jikata valve 1, another flow path switching device may be used.

[0023]

As described above, according to the present invention,
Even if the retention time of the measurement target component that arrives at the analysis unit latest is deviated due to deterioration of the column, flow rate change, or the like, the backflush timing can be automatically adjusted to the optimum state. Therefore, it is possible to effectively avoid the inconvenience that the non-measurement target component appearing after the latest measurement target component interferes with the next measurement sequence, or the measurement target component is backflushed. The measurement sequence time can be optimally shortened.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a chromatogram for explaining the basic principle of the method of the present invention.

FIG. 2 is a configuration diagram showing an example of an apparatus to which the method of the present invention is applied.

3A and 3B are diagrams showing a flow path switching state.

4 (A), (B), and (C) are diagrams showing a state of movement of a measurement target component and a non-measurement target component in a column and an analysis unit.

[Explanation of symbols]

1 ... flow path switching apparatus, 17 ... second column, 18 ... first column, 22 ... analyzer, t _A ... retention time of the measurement target component earliest reaches the analyzer, t _D ... backflush time.

Claims (1)

[Claims] 1. The second column is backflushed by a flow path switching device that connects or separates the first column and the second column provided in the preceding stage of the analysis section, and thereby,
In the flow path switching method for separating the plurality of measurement target components and the non-measurement target components, the retention time of the measurement target component that reaches the analysis unit earliest among the plurality of measurement target components, and the plurality of measurement target components Of the plurality of measurement target components, the retention time of the measurement target component that reaches the analysis unit earliest, and the ratio to the time when the measurement target component that reaches the analysis unit latest is not backflushed, and The flow path switching method is characterized in that the backflush timing is adjusted by using the ratio.