JP6394426B2 - Gas chromatograph - Google Patents

Description

  The present invention relates to a gas chromatograph used for gas chromatography (GC).

  As a detector used for gas chromatography, a thermal conductivity detector (TCD) is known. The thermal conductivity detector uses heat transfer between a heating element (filament) and a fluid (gas) flowing around the heating element. After the gas is introduced into the space in which the heating element is accommodated, the gas is discharged from the space.

  Usually, a thermal conductivity detector is provided with at least two cell spaces in which filament elements are arranged. A filament element is arranged in each cell space.

  A reference gas flows in one cell space. A carrier gas is flowed into the other cell space, and the sample gas to be analyzed is introduced. Then, the electrical outputs of the two filament elements enter the detection circuit. In the detection circuit, a correction current flows according to the difference in thermal conductivity caused by the introduction of the sample gas. In the thermal conductivity detector, the sample is detected by detecting this correction current.

  Also, a signal is obtained by controlling whether the sample gas separated by the column is introduced into the detector or only the carrier gas is introduced into the detector due to the pressure difference caused by changing the inflow location of the carrier gas. There is known a gas chromatograph equipped with a detector (see, for example, Patent Document 1).

FIG. 4 is a block diagram showing the entire conventional gas chromatograph.
A carrier gas is stored in the storage tank 102. The flow controller 104 is connected between the column 106 and the storage tank 102. A sample introduction unit 108 is connected to one end of the column 106. Here, the column 106 has a function of separating each component of the sample with time.

  The gas sent out from the column 106 is sent to one of the pipes 112 and 114 via the connecting portion 110. That is, the gas that has flowed into the pipe 112 is sent to the exhaust port 118 via the coiled pipe 116 and is discarded there.

  On the other hand, the gas flowing into the pipe 114 is sent to the detector 122 via the coiled pipe 120. Which pipe (112 or 114) the gas exhausted from the column 106 is switched to flow into is determined by the method described below.

  The carrier gas stored in the storage tank 102 is sent to the pressure regulators 126 and 128 via the pipe 124. The gas sent out from the pressure regulator 126 is sent to the pipe 112 through the valve 130. Here, the connecting portion 132 between the valve 130 and the pipe 112 is positioned between the coiled pipe 116 and the connecting portion 110.

  In addition, the gas sent out from the pressure regulator 128 is sent to the pipe 114 through the valve 134. Here, the connecting portion 136 between the valve 134 and the pipe 114 is positioned between the coiled pipe 120 and the connecting portion 110.

  As shown in FIG. 1, when the valve 130 is open and the valve 134 is closed, the pressure of the carrier gas at the connecting portion 132 is set to a predetermined pressure value by the pressure regulator 126. Here, the predetermined pressure value means a pressure sufficient to send the gas discharged from the column 106 (mixed gas of carrier gas and sample gas) to the detector 122 via the coiled pipe 120.

  On the other hand, when the valve 130 is closed and the valve 134 is open, the pressure of the carrier gas at the connecting portion 136 is set to a predetermined value by the pressure regulator 128. Here, the predetermined pressure means a pressure sufficient to send the gas discharged from the column 106 to the exhaust port 26 via the coiled pipe 116. Therefore, in this case (valve 130: closed, valve 134: open), only the carrier gas is introduced into the detector 122.

  With the switching means described above, it is possible to select whether to introduce only the carrier gas into the detector 122 or to introduce the sample gas from the column 106. Note that the valve drive circuit 138 controls the opening and closing of the valves 130 and 134.

  The exhaust gas from the column 106 and the carrier gas alone are alternately introduced into the detector 122. Therefore, the bridge output signal 140 of the detector 122 appears as an AC signal. That is, the level difference between the bridge output signal 140 due to the gas discharged from the column 106 and the bridge output signal 140 due to the carrier gas alone is caused by each component of the sample. Therefore, when the sample gas is not included, these two output signal levels are equal.

  Note that although the output voltage of the bridge output signal 140 gradually changes in level, this affects both the two signals described above. Therefore, the drift over time of the detector 122 can be eliminated by subtracting the bridge output signal level due to the carrier gas alone.

JP 53-046091 A

In Patent Literature 1, whether the sample gas is introduced into the detection unit or only the carrier gas is introduced into the detection unit is controlled by a pressure difference caused by changing the inflow location of the carrier gas.
In this method, when the sample gas is introduced into the detection unit, the sample gas is pushed to the detection unit side by the carrier gas, so that the sample gas is diluted by the carrier gas and the minimum detection amount is reduced.

The thinning of the sample gas increases when the flow rate of the carrier gas is increased (that is, when the pressure is increased), and decreases when the flow rate of the carrier gas is decreased (when the pressure is decreased). Therefore, it is preferable to reduce the carrier gas flow rate.
However, if the carrier gas flow rate is reduced too much, the sample gas cannot be switched and the sample cannot be measured. For this reason, it is important to specify an appropriate carrier gas flow rate (pressure).

  However, until now, it has been necessary to designate the carrier gas flow rate by the operator himself, and thus an appropriate carrier gas flow rate has not been designated. Therefore, there is a problem that the sample gas is thinned by the carrier gas and the minimum detection amount is lowered.

  An object of the present invention is to provide an operator with an appropriate carrier gas flow rate.

  In the gas chromatograph of the embodiment of the present invention, a column for separating a sample, and a carrier gas containing a sample component separated by the column and only the carrier gas are alternately introduced into the detection unit by changing the inflow location of the carrier gas. A detector for acquiring a signal, an analysis information input unit for inputting analysis information, a data holding unit holding data indicating a relationship between a column flow rate and a carrier gas flow rate obtained in advance, and the analysis information input The column flow rate is calculated based on the analysis information input from the unit, and the carrier gas flow rate corresponding to the calculated column flow rate is calculated using the calculated column flow rate and the data held by the data holding unit. And a calculation unit for calculating.

  The gas chromatograph of the embodiment of the present invention can calculate an appropriate carrier gas flow rate and provide it to the operator.

It is a schematic block diagram for demonstrating one Embodiment of a gas chromatograph. It is a schematic block diagram for demonstrating the carrier gas flow rate calculation function of the control part of the embodiment. It is a flowchart for demonstrating the carrier gas flow rate calculation operation | movement of the embodiment. It is the block diagram which showed the conventional gas chromatograph whole.

  In the gas chromatograph of the embodiment of the present invention, the analysis information is, for example, at least one of an inner diameter of the column, a length of the column, a temperature, and a pressure applied to the column. The analysis information is not limited to the information listed here.

  In the gas chromatograph of the embodiment of the present invention, the calculated carrier gas flow rate is displayed on the display unit, the carrier gas is input at the calculated carrier gas flow rate, or both are performed. Good.

  An appropriate carrier gas flow rate (pressure) is determined by the shape of the gas flow path and the flow rate of the sample gas. An appropriate relationship between the carrier gas flow rate and the sample gas flow rate is obtained in advance by numerical calculation such as experiment or simulation, and held in the internal memory (data holding unit) of the gas chromatograph of the embodiment of the present invention.

  Here, the appropriate relationship between the column flow rate and the carrier gas flow rate is a previously obtained relationship that represents the carrier gas flow rate at which the detection signal is larger than the column flow rate when the column flow rate is a variable. The carrier gas flow rate at which the detection signal is larger than the column flow rate is preferably a carrier gas flow rate at which the detection signal is maximized, but is not limited thereto. For example, the carrier gas flow rate in the relationship between the column flow rate and the carrier gas flow rate is a carrier gas flow rate at which the detection signal has a certain level or more, for example, a detection signal of 90% or more is obtained with respect to the maximum value of the detection signal. Any value is acceptable.

  In analysis using a gas chromatograph, an operator always inputs analysis information, that is, information on the column to be used (inner diameter and length), temperature conditions, pressure of a gas applied to the column, etc. manually or automatically. The gas chromatograph of the embodiment of the present invention automatically calculates the sample gas flow rate (column flow rate) at the column outlet using these values, and the calculated column flow rate and the value held in the internal memory (data holding unit). To determine the appropriate carrier gas flow rate. By automatically displaying the obtained carrier gas flow rate on the display unit, an appropriate carrier gas flow rate can be provided to the operator. Thereby, thinning of the sample gas due to the carrier gas can be suppressed, and the minimum detection amount can be improved.

FIG. 1 is a schematic configuration diagram for explaining an embodiment of a gas chromatograph.
The analysis channel of this gas chromatograph includes a column 4 and a detector 16. One end of the column 4 is connected to the sample vaporizing chamber 2. The column 4 is introduced from the injector 1 into the sample vaporizing chamber 2 and is vaporized to separate the sample sent by the carrier gas. The column 4 is disposed in the thermostat 3. The other end of the column 4 is connected to the detector 16.

  The detector 16 detects the sample component separated by the column 4. The detector 16 is manufactured by, for example, a MEMS (Micro Electro Mechanical Systems) process. Thereby, a small thermal conductivity detector can be realized. However, the detector 16 may be formed by a technique other than the MEMS technique such as a metal block.

  The sample gas separated in the column 4 passes through the flow path 12 and the flow path 18 in the detector 16 and the flow path 13 in which the detection unit (filament) 17 is disposed or the flow path without the detection unit (filament). 14 is sent in one direction. The gas introduced into the flow path 13 or the flow path 14 is released to the outside of the detector 16, for example, into the atmosphere via the flow path 15. One end of the channel 18 is connected to the channel 13. The other end of the flow path 18 is connected to the flow path 14. The channel 12 is connected to the channel 18 at a position between the channel 13 and the channel 14.

  A flow path to which the pipe 10 is connected and a flow path to which the pipe 11 is connected are also connected to the flow path 18. The flow path to which the pipe 10 is connected is connected to the flow path 18 at a position between the flow path 12 and the flow path 14. The flow path to which the pipe 11 is connected is connected to the flow path 18 at a position between the flow path 12 and the flow path 13.

  The carrier gas stored in the tank 6 is sent to the pressure regulator 20 through the pipe 9 and the pipe 19. The carrier gas sent out from the pressure regulator 20 is sent to the sample vaporizing chamber 2. The sample gas obtained by vaporizing the sample introduced from the injector 1 into the sample vaporizing chamber 2 is sent to the column 4 by the carrier gas and separated. The separated sample gas is sent to the detector 16 by the carrier gas.

In the detector 16, whether the sample gas flows into the flow path 13 or the flow path 14 is determined by the following method.
The carrier gas stored in the tank 6 is also sent to the pressure regulator 7 through the pipe 9. The carrier gas sent out from the pressure regulator 7 is sent to either the pipe 10 or the pipe 11 via the switching valve 8.

  When the carrier gas is sent to the pipe 10, the sample gas flowing out from the flow path 12 to the flow path 18 is pushed by the carrier gas sent from the pipe 10 and flows into the flow path 13 where the detection unit 17 is arranged. To do. Only the carrier gas flows into the flow path 14 without the detection part (filament).

  Conversely, when the carrier gas is sent to the pipe 11, the sample gas is pushed by the carrier gas sent from the pipe 11 and flows into the flow path 14 without the detection part (filament). Only the carrier gas flows into the flow path 13 where the detection unit 17 is arranged.

  It is possible to select whether to introduce the sample gas from the column 4 or only the carrier gas into the flow path 13 where the detection unit 17 is arranged by the gas switching means using the pressure difference described above. For example, by operating the switching valve 8 at a constant cycle of about 100 milliseconds, the detection unit 17 can acquire the signals of the sample gas and the carrier gas. And the chromatogram of sample gas can be obtained by taking the difference of each signal.

  A control unit 5 is provided to control the column flow rate and the carrier gas flow rate. The control unit 5 includes, for example, a microcomputer including a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), an EPROM (Erasable Programmable ROM) and the like provided in the gas chromatograph body. It is structured in the center. The control unit 5 can be realized by a workstation other than the gas chromatograph dedicated CPU or the like, for example, a workstation outside the gas chromatograph or a personal computer. The control unit 5 may be configured by a plurality of CPUs, a plurality of workstations, a plurality of personal computers, or a combination thereof.

  An analysis information input unit 23 for inputting analysis information and the like to the control unit 5 is provided. For example, a display unit 24 that displays analysis information, a carrier gas flow rate calculated by the control unit 5, and the like is provided.

  The control unit 5 controls, for example, the operations of the injector 1, the thermostatic chamber 3, the pressure regulator 7, the switching valve 8, the detector 16, and the pressure regulator 20.

FIG. 2 is a schematic block diagram for explaining the carrier gas flow rate calculation function of the control unit of this embodiment.
The configuration of the control unit 5 is, for example, a function executed by a program installed in a microcomputer and data held in the EPROM. Instead of the EPROM, an electrically erasable EEPROM (Electrically Erasable Programmable ROM) or a flash memory can be used.

The control unit 5 includes a data holding unit 21 and a calculation unit 22.
The data holding unit 21 holds data indicating the relationship between an appropriate column flow rate and carrier gas flow rate. The data holding unit 21 is configured by a part of a memory 5a made of, for example, EPROM. The data holding unit 21 may be stored in a storage medium outside the microcomputer. The storage medium may be any storage medium that can hold data indicating the relationship between an appropriate column flow rate and carrier gas flow rate. For example, a hard disk drive (HDD), a solid state drive (SSD), a flexible disk (FD), and an optical disk. , Magneto-optical disk, CD-ROM, DVD-ROM, DVD-RAM, nonvolatile memory card, and the like.

  The calculation unit 22 calculates the column flow rate based on the analysis information input from the analysis information input unit 23. In addition, the calculation unit 22 calculates an appropriate carrier gas flow rate according to the calculated column flow rate from the calculated column flow rate and the value held in the data holding unit 21.

  The analysis information input unit 23 is for inputting analysis information including the inner diameter, length, and temperature of the column 4 and the pressure applied to the column 4. For example, the analysis information input from the analysis information input unit 23 is displayed on the display unit 24 by the calculation unit 22. The analysis information input unit 23 can also input information other than the analysis information, for example, a carrier gas flow rate.

The relationship between the appropriate column flow rate and carrier gas flow rate held in the data holding unit 21 may be a value obtained in advance by experiments, or a value obtained in advance by numerical calculation such as theoretical calculation or simulation.
Further, when calculating an appropriate carrier gas flow rate by the calculation unit 22, only one value held in the data holding unit 21 may be used, or a plurality of values may be used.

  The calculation of the column flow rate and the appropriate carrier gas flow rate by the calculation unit 22 is realized by, for example, a CPU program. The data holding unit 21 is data stored in the memory 5a connected to the CPU. The analysis information input unit 23 is an input device such as a keyboard or a touch panel connected to the CPU. The display unit 24 is a display device such as a monitor or a digital display connected to the CPU.

FIG. 3 is a flowchart for explaining the carrier gas flow rate calculating operation of this embodiment.
When analysis information used in the gas chromatograph is input to the analysis information input unit 23 such as a keyboard (step S1), the column flow rate is calculated by the calculation unit 22 (step S2).

  The calculation unit 22 refers to data indicating an appropriate column flow rate and carrier gas flow rate held in the data holding unit 21 (step S3). The calculation unit 22 calculates an appropriate carrier gas flow rate from the calculated column flow rate and the value held in the data holding unit 21 (step S4).

  The calculated appropriate carrier gas flow rate is displayed on the display unit 24, or is provided to the operator by voice from a speaker, or both are provided to the operator (step S5). Further, the calculated appropriate carrier gas flow rate may be automatically input at a location where the carrier gas flow rate is input.

  The control unit 5 controls the pressure regulator 7 based on the value of the carrier gas flow rate displayed on the display unit 24.

  Thus, the chromatograph of this embodiment automatically calculates an appropriate carrier gas flow rate and provides it to the operator. Thereby, thinning of the sample gas due to the carrier gas can be suppressed, and the minimum detection amount can be improved.

  As mentioned above, although embodiment of this invention was described, the structure, arrangement | positioning, a numerical value, material, etc. in embodiment are examples, This invention is not limited to this, This invention described in the claim Various changes can be made within the range.

4 column 16 detector 21 data holding unit 22 calculation unit 23 analysis information input unit 24 display unit

Claims (3)

A column for separating the sample;
A detector for acquiring a signal by alternately introducing a carrier gas containing a sample component separated by the column and only the carrier gas into the detector by changing the inflow location of the carrier gas;
An analysis information input unit for inputting analysis information;
A data holding unit holding data indicating the relationship between the column flow rate and the carrier gas flow rate obtained in advance;
A column flow rate is calculated based on the analysis information input from the analysis information input unit, and the calculated column flow rate and the data held by the data holding unit are used according to the calculated column flow rate. A gas chromatograph comprising: a calculation unit that calculates a carrier gas flow rate.   The gas chromatograph according to claim 1, wherein the analysis information is at least one of an inner diameter of the column, a length of the column, a temperature, and a pressure applied to the column. On the display unit of the carrier gas flow rate the calculated gas chromatograph according to 請 Motomeko 1 or 2.

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