JP2800621B2 - Gas chromatograph - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas chromatograph for analyzing components of exhaust gas and other sample gases discharged from automobiles, combustion equipment and the like with high sensitivity (up to the order of ppb).

[0002]

2. Description of the Related Art For example, exhaust gas from automobiles (gasoline and diesel internal combustion engines) is, for example, from C1 (methane) to C1 (methane).
Conventionally, all components must be measured with a single gas chromatograph, because they contain a wide range of compounds up to about 2 (dodecane) and the other is that the content of each component is very small. Was impossible. for that reason,
Conventionally, four types of analysis, methane (C1) -based analysis, ethane and ethylene (C2) -based analysis, C3 and C4-based analysis, and C5-C12-based analysis, are separately performed. I was doing.

[0003]

As described above, the conventional one
In order to measure the types of exhaust gas, it was necessary to repeat the same measurement four times while exchanging columns and the like, and the operation was very complicated. The analysis limit of each component is also 100 ppb.
This was not enough for the analysis of trace components.

The present invention has been made to solve such a problem, and an object of the present invention is to analyze a sample gas containing a wide range of components by a simple operation at a time and to achieve a high level of analysis. It is an object of the present invention to provide a gas chromatograph device capable of performing with high sensitivity.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a gas chromatograph apparatus according to the present invention comprises: a) a sample gas measuring section provided with a measuring pipe having a predetermined volume; b) a precolumn and a flow column. A component separation unit that includes a channel switching valve and separates only the analyte from the sample gas that has passed through the precolumn before the channel switching valve is switched.c) A concentration column that includes a concentration column, a cooler, and a heater and is cooled by a cooler. A gas concentrating unit that adsorbs the analyte to be analyzed in the sample gas and desorbs the adsorbed component by heating the concentration column with a heater to concentrate the sample gas.d) Each of the analysis unit equipped with a main column and a detector. E) controlling the switching timing of the flow path switching valve of the component separation section of each flow path to provide a different analysis target component for each flow path. It is characterized in that it comprises a control unit for concentrating the sample gas by was circulated to control the cooler and the heater of the gas concentration of each flow channel that the.

[0006]

The control section limits the sample gas flowing through each flow path to an arbitrary range by changing the switching timing of the flow path switching valve of the component separation section of each flow path. For this reason, even a sample gas containing a wide range of components is automatically divided into a plurality of sample gases containing different analytes (separated components to be analyzed) without any complicated operation, and each component is separated. Perform analysis for each range. Further, the control unit controls the cooler and the heater of the gas concentrating unit provided in each flow path, thereby concentrating the sample gas in each flow path. For this reason,
Trace components can also be measured with high accuracy in the analysis unit.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A gas chromatograph for exhaust gas analysis according to one embodiment of the present invention will be described with reference to FIGS. The gas chromatograph apparatus of the present embodiment is roughly composed of a pre-processing unit 11, a concentration unit 12, a focusing unit 15, an analysis unit 16, and a control unit 17, as shown in FIG. In the pre-processing unit 11, the sample gas (exhaust gas from an automobile or the like) sucked from the sample inlet 14 by the pump P is measured and supplied to two flow paths, and the sample gas flowing through one of the flow paths is C1 to C1. The sample gas flowing through the other flow path contains only the components C1 to C6. The concentrating unit 12 is used in the course of the processing in the pre-processing unit 11, and condenses the sample gas in each flow path to increase the concentration of the hydrocarbon component to be analyzed in the sample gas. The focusing unit 15 further narrows the width of the peak of each analysis target component in each concentrated sample gas and increases the height. The analysis unit 16 detects each component contained in each concentrated sample gas using a column (main column) and a detector. The control unit 17 performs switching of a switching valve, control of a cooler and a heater, and the like in order to realize the operation of each unit.

Next, the structure of the gas chromatograph for exhaust gas analysis of this embodiment will be described in detail with reference to the detailed system diagram of FIG.

(1) Pretreatment unit 11 A first switching valve RV1 and a second switching valve RV2 are connected between the sample inlet 14 and the pump P. The first and second switching valves RV1, RV2 are both octagonal valves, and measuring pipes 30, 31 are respectively connected between two ports of each valve. The sample gas taken into the gas chromatograph device of the present embodiment from the sample inlet 14 is measured and collected by the measuring tubes 30 and 31 of the first and second switching valves RV1 and RV2, respectively. Thereafter, the sample gas sampled by each of the measuring tubes 30 and 31 is supplied to a flow path (hereinafter, referred to as a first switching valve RV) provided in parallel in the gas chromatograph apparatus of the present embodiment.
1 pass through the first flow path, and the flow path corresponding to the second switching valve RV2 passes through the second flow path). In the pre-processing unit 11, a third switching valve RV3 and a fourth switching valve RV4 are provided in the first and second flow paths, respectively. Third and fourth switching valves R
V3 and RV4 are both 10-way valves.
The pre-columns 32 and 35, the choke columns 33 and 36, and the dummy columns 34 and 37 are connected,
37 are connected to pressure controllers PC1 and PC2. Further, the first and second switching valves RV
1. Mass flow controller MFC1 via RV2,
Each of them is also connected to the MFC2.

(2) Concentrating Unit 12 As shown in FIG. 1, the concentrating unit 12 is composed of two columns 40 and 41 filled with a usual packing material.
1 is connected to two ports of the third switching valve RV3 and the fourth switching valve RV4, respectively. As shown in FIG. 4, an insulated closed space is provided around both the columns 40 and 41 of the concentration unit 12. The valve LNV <b> 1 is opened to allow liquid nitrogen (LN ₂ ) to flow therethrough. 4
0 and 41 can be cooled to about -170 ° C.
The columns 40 and 41 are made of metal, and can be heated by power supply HT1.

(3) Focusing section 15 One focusing column 51, 52 is provided for each of the first and second flow paths. As shown in FIG. 5, the focusing columns 51 and 52 are configured by capillary columns, and a heat-insulated space 53 and a heater HT3 are provided around the focusing columns 51 and 52. As in the case of the concentrating unit 12, by opening the valve LNV2 and flowing liquid nitrogen (LN ₂ ) into the heat insulating space 53, the focusing columns 51 and 52 can be cooled, and by supplying a current to the heater 56 by the power supply HT2. , Heating can be performed. Both columns 51, 52
Can be heated by another heater HT3, and the columns 51 and 52 can be heated.
The internal temperature can be changed from about 40 to 180 ° C. in accordance with the temperature.

(4) Analyzer 16 Main columns 61 and 62 and detectors 63 and 64 are provided for the first and second flow paths, respectively. In this embodiment, a capillary column is used for the main columns 61 and 62, but this may be a packed column.
Generally, a flame ion detector (FID) is used as the detector, but another detector may be used. Like the focusing unit 15, the analysis unit 16 also has a heater HT4 for heating the entire room, and can change the temperature from about 40 to 180 ° C.

(5) Controller 17 As shown in FIG. 3, the controller 17 includes the pump P, the switching valves RV1 to RV4, the mass flow controller MFC
1, MFC2, pressure controller PC1, PC
2. Connected to the liquid nitrogen valves LNV1, LNV2, heaters (or heater power supplies) HT1 to HT4, etc., and drive them at each timing described later. The control unit 17 may be configured by a microcomputer, or may be configured by a sequencer and a relay.

Next, the procedure of analyzing the exhaust gas by the gas chromatograph of this embodiment will be described step by step.

(1) Measurement First, the flow paths of the first and second switching valves RV1, RV2 are set to the positions indicated by the solid lines in FIG. The sample gas (e.g., exhaust gas from an automobile) sucked from the inlet 14 is supplied to the first switching valve R
The gas is discharged by the pump P through a path of V1-measuring pipe 30-first switching valve RV1-second switching valve RV2-measuring pipe 31-second switching valve RV2-valve 28.

When the sample gas has been sufficiently introduced into the two measuring pipes 30 and 31, the control unit 17 controls the two switching valves RV1 and RV2.
Is rotated by 45 ° to set the flow path to the position indicated by the dotted line, and the mass flow controllers MFC1 and MFC2 are activated to supply the carrier gas to the first and second switching valves RV1 and RV2. Thereby, the mass flow controller MFC1-the first switching valve RV1-the measuring pipe 30-the first switching valve RV
1—The flow path of the third switching valve RV3 is configured, and the measuring pipe 3
A predetermined amount (for example, 50 ml) of the sample gas stored in 0 is pushed by the carrier gas from the mass flow controller MFC1 and sent to the third switching valve RV3. Similarly, the sample gas in the measuring pipe 31 is sent to the fourth switching valve RV4 by the mass flow controller MFC2.

(2) Concentration The flow paths of the third and fourth switching valves RV3 and RV4 are initially located at the positions indicated by the dotted lines in FIG.
Is supplied from the third switching valve RV3 to the column 40 of the concentration unit 12. In the concentrating unit 12, the control unit 17 opens the valve LNV1 before that, and the column 40 is cooled by liquid nitrogen (LN ₂ ). The sample gas from the third switching valve RV3 is flowed from the end A to the end B of the column 40, during which the hydrocarbon component in the sample gas is adsorbed on the surface of the cooled filler. The sample gas that has passed through the column 40 of the concentrating unit 12 (which does not already contain a hydrocarbon component to be analyzed) returns to the third switching valve RV3 and is discharged to the outside (VENT on the left side in FIG. 1). The same applies to the second flow path (the fourth switching valve RV4 and the column 41).

After a predetermined amount of carrier gas has been sent out by the mass flow controller MFC1, the control unit 17 rotates the third switching valve RV3 by 36 ° to set the flow path to the position indicated by the solid line. Then, the liquid nitrogen valve LNV1 of the concentrating unit 12 is closed, and a current is supplied from the power supply HT1 to each of the columns 40 and 41, thereby heating the columns 40 and 41 and simultaneously activating the pressure controller PC1 to activate the carrier gas having a predetermined pressure. Through the third switching valve RV3.
Send to 2. At this time, contrary to the above, the carrier gas flows from the end B of the column 40 to the end A. Thereby, each component previously adsorbed to the packing material of the column 40 in the low temperature state is desorbed from the packing material. However, since the temperature of the column 40 is sufficiently high, each component is desorbed at a high speed and the sample is removed. Gas concentration is performed. The same applies to the second flow path (the fourth switching valve RV4 and the column 41).

(3) Separation The concentrated sample gas returned to the third switching valve RV3 passes through the pre-column 32. In the pre-column 32, the concentrated sample gas is separated in accordance with the number of carbon atoms.
Sent to The control unit 17 sets the third switching valve RV3 to 3 when the components up to C12 have just passed through the pre-column 32.
Rotate 6 ° to switch the flow path to the position indicated by the dotted line. At this time, the high carbon number component of C13 or more is in the pre-column 32 or in the flow path before it. The carrier gas from the pressure controller PC1 flows through the pre-column 32 through the third switching valve RV3 in the direction opposite to the previous direction, and pushes back those high-carbon components (C13 or more) to the outside (from the choke column 33). VENT). Choke column 33
Is a kind of dummy column having the same flow path resistance as a main column 61 described later.

The concentrated sample gas returned from the concentrating unit 12 to the fourth switching valve RV4 is basically subjected to the same separation as described above, but in this case (second flow path), the fourth switching valve is used. The RV4 flow path switching timing is set to the third
By making the switching valve RV3 earlier than the switching valve RV3, only the low carbon number component below C6 is sent to the focusing unit 15, and the higher carbon number component (more than C7) is discharged from the precolumn 35 to the outside. Thus, in the first channel, C1 to C12
In the second flow path, only the components from C1 to C6 are sent to the focusing unit 15. The switching timing of the third switching valve RV3 and the fourth switching valve RV4 is determined in advance by performing preliminary measurement.

(4) Focusing The focusing section 15 further concentrates the concentrated sample gas by a method similar to the above-described concentration section 12. That is,
The first flow path will be described. First, the liquid nitrogen valve L
The column 51 is cooled to a low temperature with liquid nitrogen by opening the NV2 (FIG. 5), and the concentrated sample gas is passed through the column. As a result, the analysis target component in the sample gas is adsorbed on the inner wall of the column (capillary column) 51. Thereafter, by heating the column 51 by the heater 56, the adsorbed components are desorbed at a high speed. The same applies to the second flow path.

(5) Analysis The sample gas in the first flow path containing only the component of C12 or less sent from the focusing unit 15 via the connector 60 passes through the main column 61, where each component is separated. . The detector 63 mainly measures the slow separated component, that is, the C6 to C12 component among the separated components. In the second flow path, the sample gas contains only components of C6 or less, and the components separated through the main column 62 are measured by the detector 64 from the beginning with high accuracy. Thereby, the low carbon number components of C1 to C6 are measured with high accuracy by the detector 64 in the second flow path, and the high carbon number components of C6 to C12 are measured with high accuracy by the detector 63 in the first flow path. Done.

FIG. 6 shows a chromatogram of a standard gas containing only the C1 to C12 components measured by the gas chromatograph of this embodiment, and FIG. 7 shows a chromatogram obtained by measuring the exhaust gas of an actual automobile. As a result of analyzing the area of each peak in the graph of FIG. 7 by comparing it with the area of the corresponding peak in the graph of FIG. 6, in the gas chromatograph apparatus of this example, 2.5 ppb (* 1 peak in the upper center of FIG. 7) was obtained. ) And
As little as 0.5ppb (* 2 peak) can be measured.

[0024]

In the gas chromatograph apparatus according to the present invention, since the control unit automatically separates the sample gas in each arbitrary range, complicated operations can be performed even for a sample gas containing a wide range of components. The analysis for each component range can be performed without necessity. Further, since the sample gas in each flow path is concentrated, trace components can be measured with high accuracy.

[Brief description of the drawings]

FIG. 1 is a flow chart of a high-sensitivity gas chromatograph for exhaust gas analysis according to one embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a gas chromatograph device of an embodiment.

FIG. 3 is a control system diagram of the gas chromatograph device of the embodiment.

FIG. 4 is a sectional view showing a configuration of a gas concentrating unit.

FIG. 5 is a configuration diagram of a focusing unit.

FIG. 6 is a chromatogram of a standard gas prepared by the gas chromatograph of the example.

FIG. 7 is a chromatogram of an exhaust gas of an automobile created by the gas chromatograph device of the embodiment.

[Explanation of symbols]

11: Pretreatment unit 12: Concentration unit 14: Sample introduction port 15: Focusing unit 16: Analysis unit 17: Control unit RV1, RV2: Switching valve (eight-way valve) RV3, RV4: Switching valve (ten-way valve) MFC1, MFC2 ... Mass flow controller PC1, PC2 ... Pressure controller HT1, HT2 ... Power supply for heater HT3, HT4
... heaters LNV1, LNV2 ... liquid nitrogen valves 30, 31 ... measuring tubes 32, 35 ... pre-columns 33, 36 ... choke columns 34, 37 ... dummy columns 40, 41 ... concentration columns 51, 52 ... focusing columns 61, 62 ... main columns 63, 64 ... detector

Claims (1)

(57) [Claims] 1. a) a sample gas measuring section having a measuring tube having a predetermined volume; b) a precolumn and a flow path switching valve, wherein the sample gas passes through the precolumn before the flow path switching valve is switched. A component separation section for separating only the component to be analyzed c) A concentration column, a cooler and a heater are provided, and the component to be analyzed in the sample gas is adsorbed by the concentration column cooled by the cooler and adsorbed by heating the concentration column with the heater. A gas concentrating unit for desorbing components and condensing the sample gas d) A capillary column, a cooler, and a heater are provided. The capillary column cooled by the cooler adsorbs the target component in the sample gas, and the capillary column is heated by the heater. Focusing unit that desorbs the adsorbed target component and sharpens the peak of the target component in the sample gas. E) Main column and A plurality of analysis channels each having an element of the analysis unit having a detector are provided. F) By controlling the switching timing of the channel switching valve of the component separation unit of each channel, a different analysis channel is provided for each channel. A gas chromatograph apparatus comprising: a control unit for circulating a target component and concentrating a sample gas by controlling a cooler and a heater of a gas concentrating unit in each flow path.