JPH0694693A - Method and apparatus for analyzing sample - Google Patents

Abstract

PURPOSE:To chromatographically separate the components to be measured of a sample by injecting a large quantity of the sample into a separation column within a short time by raising the head pressure of the separation column for a definite time to collect the sample and feeding the sample to the separation column before returning the head pressure of the column to the original pressure. CONSTITUTION:A suction pump 11 is operated to introduce a sample into a sample suction pipe 12. The sample flows through the connection ports 3e, 3f weighing tube 39 connection port 3c, 3d of a sample collecting valve 3. Therefore, the weighing tube 3g is filled with the sample. An electric pressure control valve 6 is operated in this state to raise the pressure of carrier gas to raise the head pressure of a separation column 5 and the collecting valve 3 is turned ON to bring the inner passage of the valve 3 to a broken line state. Therefore, the sample in the weighing tube 3g is fed by the carrier gas to enter the separation column 5 and the components to be measured in the sample are chromatographically separated. The fluid eluted from the separation column 5 is detected and a chromatogram showing the concns. of the respective components in the sample 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 highly sensitively analyzing a component to be measured in a sample by using a gas chromatograph and an apparatus therefor, and particularly, to a sample with a head pressure of a separation column kept high for a certain period of time. Is introduced into a separation column in a short time, and then the head pressure of the separation column is returned to the original pressure to optimize the chromatographic separation, and to a sample analysis method and apparatus.

[0002]

2. Description of the Related Art As is well known, a gas chromatograph is widely used as an apparatus for analyzing a component to be measured in a sample with high sensitivity. FIG. 6 is a diagram for explaining a conventional example of a method and an apparatus for analyzing a sample using a gas chromatograph, in which 1 is a carrier gas supply source, 2 is a mass flow meter, 3 is a sampling valve, 4 is an injection port, 5 is a separation column composed of, for example, a capillary column, 7a is a split vent, 7b is a septum purge vent, 13 is a septum purge controller for adjusting the flow rate of the fluid which is divided by the injection port 4 and flows to the septum purge vent 7b, 13a is the inlet of the septum purge controller 13, 13b is the septum purge controller 1
Exit 3 14 is a back pressure regulator that regulates the flow rate of the fluid that is divided by the inlet 4 and flows to the split vent 7a.
14a is the inlet of the back pressure regulator 14, and 14b is the back pressure regulator 1.
The outlet 4 and 14c are pressure gauges.

In the conventional example having such a structure,
Initially, the sampling valve 3 is off, and its internal flow path is in a solid line connection state. In this state, the carrier gas supply source 1
The carrier gas supplied from the mass flowmeter 2 → passes through the first and second connection ports 3a and 3b of the sampling valve 3 and the injection port 4
Is divided into three directions. The carrier gas as the first divided stream divided in this way is separated by the septum purge controller 13
After the flow rate is adjusted by (1), it is discharged through the septum purge vent 7b. Further, the carrier gas as the second split stream divided at the inlet 4 is discharged through the split vent 7a after the pressure is adjusted by the back pressure adjuster 14. Further, the carrier gas as the third split stream divided at the inlet 4 is guided to the separation column 5, passed through a detector (not shown), and then discharged.

When the suction pump 11 is operated, a sample such as ambient air is introduced from the sample suction pipe 12,
The sample is the fifth and sixth connection ports 3e, 3f of the sampling valve 3.
→ 3 g of measuring pipe → 3rd and 4th connection ports 3c of the sampling valve 3
3d → flows through the flow path of the suction pump 11. Therefore, the inside of the measuring tube 3g is filled with the sample. When the sample collection valve 3 is turned on in this state, the internal flow path is in a broken line connection state. Therefore, the sample in the measuring pipe 3g is carried to the carrier gas, introduced into the injection port 4, and part of the sample is introduced into the separation column 5. Therefore, the component to be measured in the sample is chromatographically separated and then guided to a detector (not shown).

FIG. 8 is a diagram showing a chromatogram of the ambient air analyzed in this way, in which the vertical axis represents the intensity of the detection signal and the horizontal axis represents the retention time (unit is minutes). There is. Further, FIG. 7 is a chromatogram showing a result of analyzing a trace amount of a component to be measured contained in a hydrocarbon mixed gas having about 4 to 10 carbon atoms by using the conventional example as described above.

As is clear from the chromatograms shown in FIGS. 7 and 8, the peak height of the component to be measured is insufficient, and it is desired to collect a large amount of sample to improve the sensitivity.

[0007]

However, in such a conventional example, the amount of the sample introduced into the separation column 5 is determined by the split ratio of the inlet 4 and the internal volume of the measuring tube 3g. There was such a problem. That is, in the usual case, the minimum split ratio that does not impair the analysis accuracy is about 10: 1 in the case of a capillary column having an inner diameter of 0.25 mm. In particular, in order to obtain the optimum separation, there is a problem that it is difficult to introduce a large amount of sample with the device as shown in FIG.

The present invention has been made in order to solve the above-mentioned problems of the conventional examples and the like in such a situation, and a large amount of sample is injected into a separation column in a short time so that the sample in the sample can be removed. An object of the present invention is to provide a sample analysis method and apparatus for chromatographically separating measurement components.

[0009]

The present invention is a method for analyzing a component to be measured contained in a sample using a gas chromatograph, in which the head pressure of the separation column is increased for a certain period of time when the sample is collected by a sampling valve. The above problem is achieved by collecting the sample in this state and transporting it to the separation column, and then returning the head pressure to the original pressure.

Similarly, the present invention controls the carrier gas supply source and the carrier gas pressure supplied from the carrier gas supply source in an apparatus for analyzing a measured component contained in a sample using a gas chromatograph. A pressure control valve, an inlet for dividing a fluid whose pressure is controlled by the pressure control valve at a fixed ratio, a sampling valve having a metering tube for sampling a sample in the metering tube, and a sample sampling valve And a separation column for chromatographically separating the sample,
The above problem is solved by returning the head pressure to the original pressure after the sample is collected and conveyed to the separation column in a state where the head pressure of the separation column is increased for a certain time when the sample is collected by the sample collection valve. Is.

Similarly, the present invention adjusts the carrier gas supply source and the flow rate of the carrier gas supplied from the carrier gas supply source in an apparatus for analyzing a component to be measured contained in a sample using a gas chromatograph. A mass flow meter, a sampling valve having a metering tube for sampling a sample in the metering tube, and an inlet for diverting a fluid delivered from the sample collecting valve into first to third flows at a constant ratio. A separation column for chromatographically separating the component to be measured in the sample supplied with the first partial flow, a pressure control valve for controlling the pressure of the second partial flow to control the head pressure of the separation column, and the third partial flow A pressure reducing valve for adjusting the pressure and a fluid resistor are provided.When the sample is collected by the sampling valve, the head pressure of the separation column is increased for a certain period of time and then the sample is conveyed to the separation column. It is obtained by solving the problems by returning to the original pressure.

[0012]

The present invention operates as follows. That is, when the pressure control valve is activated to increase the carrier gas pressure to increase the separation column head pressure and then the sampling valve is turned on, the sample in the measuring pipe is transferred to the carrier gas and separated into the separation column. And the components to be measured in the sample are chromatographically separated. The fluid eluted from the separation column is detected by the detector and gives a chromatogram showing the concentration of the measured component in the sample.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a diagram for explaining the configuration of the embodiment of the present invention. In the figure, the same symbols as those in FIG. 6 are used with the same meanings, and duplicate explanations are omitted. Further, an electric pressure control valve 6 is arranged between the carrier gas supply source 1 and the inlet 4, and a sampling valve 3 is arranged downstream of the inlet 4.

In the embodiment of the present invention having such a structure, first, the sampling valve 3 is turned off and its internal flow path is in a solid line connection state. In this state, the carrier gas supplied from the carrier gas supply source 1 passes through the electric pressure control valve 6 and is then split at the injection port 4 at a constant ratio to flow in two directions. The carrier gas as the first split flow divided in this way is supplied to the first and second connection ports 3 of the sampling valve 3.
After passing through a and 3b, it is guided to the separation column 5 and then discharged. The other carrier gas that has been split is used as the pressure reducing valve 9
-> Fluid resistor 10-> It is discharged through the septum purge vent 7b.

When the suction pump 11 is operated, a sample such as ambient air is introduced from the sample suction pipe 12, and the sample is connected to the fifth and sixth connection ports 3e and 3f of the sampling valve 3 → measuring pipe 3g → sample. It flows through the flow paths of the third and fourth connection ports 3c and 3d of the sampling valve 3. Therefore, the inside of the measuring tube 3g is filled with the sample. In this state, when the electric pressure control valve 6 is actuated to increase the carrier gas pressure and the head pressure of the separation column 5 and then the sampling valve 3 is turned on, its internal flow path is broken. Connected. Therefore, the sample in the measuring pipe 3g is carried by the carrier gas and guided to the separation column 5, and the component to be measured in the sample is chromatographically separated. The fluid eluted from the separation column 5 is detected by a detector (not shown) and gives a chromatogram showing the concentration of each component contained in the sample.

FIG. 2 shows a carbon number of 4 to 1 using the embodiment of the present invention.
6 is a time chart for explaining an operation of analyzing a hydrocarbon mixed gas of about 0, where (1) shows the head pressure of the separation column, (2) shows the temperature of the separation column, and (3) ) Indicates the on / off operation of the sampling valve, and (4)
Indicates the on / off operation of the suction pump. Further, FIG. 3 shows a chromatogram obtained by analyzing a mixed gas of hydrocarbons having about 4 to 10 carbon atoms using the example of the present invention, and FIG. 4 shows a chromatogram obtained by analyzing an environmental sample using the example of the present invention. Show.

The operation of the embodiment of the present invention will be described in more detail below with reference to FIGS. First, the present inventors set the analysis conditions as follows. That is, the sampling valve 3
Temperature of 120 ° C., separation column 5 is a J & W company DB-1 (length 60 m, inner diameter 0.25 mm, membrane pressure 1.0 μm) capillary column, detector (not shown) is FID (hydrogen flame detector), and the detector Temperature is 250 ° C, septum purge flow rate is 2 ml / min., And the content volume of 3 g of measuring pipe is 10 ml.
And

Under such analysis conditions, a mixed gas of hydrocarbons having about 4 to 10 carbon atoms was analyzed according to the time chart of FIG. That is, as shown in FIG. 2A, the head pressure of the separation column 5, that is, the column tip pressure is A (+99 ps).
i / min.) → B (+100 psi) → C (-99p
si / min.) → D (+25 psi).

Further, as shown in FIG. 2 (2), the temperature of the separation column 5 is E (-60 ° C) → F (+ 20 ° C / mi).
n.) → G (0 ° C) → H (+ 5 ° C / min.) → I
The temperature was changed like (+ 250 ° C). Further, as shown in (4) and (3) of FIG.
It was turned on for 0 minutes, and 0.1 minutes after that, 1.1 minutes from the beginning, the sampling valve 3 was turned on.

When the sampling valve 3 is turned on with the head pressure of the separation column 5 being high as described above, as described above,
A large amount of sample in the measuring tube 3g is transported to the carrier gas and introduced to the separation column 5 in a short time. After that, the head pressure of the separation column 5 is reduced by the action of the electric pressure control valve 6 as shown in FIG.
The original pressure is restored as indicated by C and D, and the component to be measured in the sample is chromatographically separated. Also,
The fluid eluted from the separation column 5 is detected by a detector (not shown) and gives a chromatogram as shown in FIG. 3 showing the concentration of each component in the sample.

As is clear from the comparison between FIG. 3 thus obtained and FIG. 6, by using this embodiment, a hydrocarbon mixed gas having about 4 to 10 carbon atoms can be obtained. It can be seen that the measurement can be performed with a sensitivity as high as about 50 times that in the case. In addition, by introducing environmental air from the sample suction pipe 12,
When the analysis as described in detail in Example 1 is performed, a chromatogram as shown in FIG. 4 is obtained. As is clear from comparison between this figure and FIG. 8, by using this example, the component to be measured in ambient air can be measured with about 50 times higher sensitivity than in the case of the conventional example.

On the other hand, FIG. 5 is a structural explanatory view for explaining another embodiment of the present invention. In the figure, the same symbols as those in FIG. 1 are used with the same meanings, and duplicate explanations are omitted here. Further, 2 is a mass flow meter, 8 is a pressure transmitter, 9 is a pressure reducing valve, 1
0 is a fluid resistor. In another embodiment of the present invention having such a configuration, first, the sampling valve 3 is turned off, and its internal flow path is in a solid line connection state. In this state,
The carrier gas supplied from the carrier gas supply source 1 is
After passing through the mass flow meter 2, the flow passes through the first and second connection ports 3 a and 3 b of the sampling valve 3 and is branched into three directions at the injection port 4.

The carrier gas as the first split stream thus split is introduced into the separation column 5 and then discharged. Further, the carrier gas as the second split flow is discharged through the electric pressure control valve 6 → split vent 7a. Further, the carrier gas as the third split stream is used as the pressure reducing valve 9
-> Fluid resistor 10-> It is discharged through the septum purgement 7b.

When the suction pump 11 is operated, a sample such as ambient air is introduced from the sample suction pipe 12,
The sample is the fifth and sixth connection ports 3e, 3f of the sampling valve 3.
→ 3 g of measuring pipe → 3rd and 4th connection ports 3c of the sampling valve 3
It flows in the flow path of 3d. Therefore, the inside of the measuring tube 3g is filled with the sample. When the sample collection valve 3 is turned on in this state, the internal flow path is in a broken line connection state. Therefore, the sample in the measuring pipe 3g is carried by the carrier gas and guided to the separation column 5, and the component to be measured in the sample is chromatographically separated. The fluid eluted from the separation column 5 is detected by a detector (not shown) and gives a chromatogram showing the concentration of each component in the sample.

The present invention is not limited to the embodiment shown in FIGS. 1 and 5, and various modifications are possible. For example, the sampling valve 3 may be a 10-port sampling valve. Is. Further, the sample introduced into the measuring pipe 3g may be not only a gas sample but also a liquid sample, and the measuring pipe may be built in the sampling valve 3.

[0026]

As described above in detail, according to the present invention, even a gas sample of 10 ml can be introduced into the separation column 5, so that a very small amount of the sample to be measured contained in the sample can be measured. There is an advantage that the components can be analyzed with high sensitivity. In addition, the standard valve system is adopted to facilitate automation, and the MSD (Mas
s Select Detector) or the like can be used, and thus there is an advantage that an analysis with high sensitivity and high selectivity can be performed.

Therefore, according to the present invention, a sample analysis method and apparatus capable of injecting a large amount of sample into the column in a short time and analyzing the component to be measured in the sample with high sensitivity can be realized.

[Brief description of drawings]

FIG. 1 is a configuration explanatory view for explaining an embodiment of the present invention.

FIG. 2 is a time chart for explaining the operation of the embodiment of the present invention.

FIG. 3 is a chromatogram created using an example of the present invention.

FIG. 4 is a chromatogram created using an example of the present invention.

FIG. 5 is a configuration explanatory view for explaining another embodiment of the present invention.

FIG. 6 is a configuration explanatory view for explaining a conventional example.

FIG. 7 is a chromatogram created by using an example of the present invention.

FIG. 8 is a chromatogram created using an example of the present invention.

[Explanation of symbols]

 1 Carrier gas supply source 2 Mass flow meter 3 Sampling valve 4 Injection port 5 Separation column 6 Electric pressure control valve 7a Split vent 7b Septum purge vent 8 Pressure transmitter 9 Pressure reducing valve 10 Fluid resistor

Claims (9)

[Claims] 1. A method for analyzing a component to be measured contained in a sample using a gas chromatograph, wherein the sample is collected with a sampling valve while the head pressure of a separation column is kept high for a certain period of time. The sample pressure is returned to the original pressure after being conveyed to the separation column. 2. The method for analyzing a sample according to claim 1, wherein the separation column is a capillary column. 3. The method for analyzing a sample according to claim 1, wherein the sample is a gas sample. 4. A carrier gas supply source, a pressure control valve for controlling the carrier gas pressure supplied from the carrier gas supply source, and a fluid whose pressure is controlled by the electric pressure control valve is divided at a fixed ratio. An inlet, a sample collection valve having a metering tube for collecting a sample in the metering tube, and a separation column for chromatographically separating a component to be measured in the sample conveyed from the sample collecting valve, A sample characterized by returning the head pressure to the original pressure after the sample is collected and conveyed to the separation column in a state where the head pressure of the separation column is raised for a certain time when the sample is collected by the sample collection valve. Analyzer. 5. The sample analyzer according to claim 4, wherein the separation column is a capillary column. 6. The sample analyzer according to claim 4, wherein the sample collection valve is a 6-port sample collection valve having a measuring pipe. 7. The sample analyzer according to claim 4 or 5, wherein the sample collecting valve is a 10-port sample collecting valve having a measuring pipe. 8. A carrier gas supply source, a mass flow meter for adjusting the flow rate of a carrier gas supplied from the carrier gas supply source, a sampling valve having a measuring pipe for collecting a sample in the measuring pipe, An inlet for dividing the fluid delivered from the sample collection valve into first to third streams at a fixed ratio, and a separation column for chromatographically separating the components to be measured in the sample supplied with the first split stream. A pressure control valve for controlling the pressure of the second split stream to control the head pressure of the separation column; a pressure reducing valve for adjusting the pressure of the third split stream; and a fluid resistor. An apparatus for analyzing a sample, wherein the sample pressure is returned to the original pressure after the sample is sampled and conveyed to the separation column in a state where the head pressure of the separation column is increased for a certain time at the time of sample collection. 9. The sample analyzer according to claim 8, wherein the separation column is a capillary column.