JPH06167482A - Volatile hydrocarbon continuously automatic analyzer - Google Patents

Abstract

PURPOSE:To analyze with high sensitivity, high separation by connecting one of sampling valves to a packed column and the other to a capillary column through a thermal desorption cold trap injector (TCT). CONSTITUTION:A sample fed to a sample supply unit 19 is fed to a sampling valve 2 via vent holes 15, 14 of a sampling valve 1 while storing in a sample loop 17, and also stored in a sample loop 3. Then, the valve 1 is switched, the sample in the loop 17 is fed to a packed column 44 via the vent holes 14, 13, a connection passage 41 by helium from a supply unit 18, separated and detected by a detector 42. On the other hand, the valve 2 is switched, the sample in the loop 3 is fed to a precolumn 5 of a TCT by helium from a supply unit 29, and high boiling point component except an object component is collected. Then, the valve 2 is switched, a cold trap 6 is quickly heated by a heater 61, helium is introduced, and trapped component is guided to a capillary column 8 via a communication passage 9, separated and detected by a detector 42.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous automatic volatile hydrocarbon analyzer.

[0002]

2. Description of the Related Art Conventionally, in the analysis of volatile hydrocarbons, a sample is manually collected in a collection tube, and the collection tube is set in an analyzer for each analysis. in this case,
It was necessary to condition the collection tube every time a sample was collected, which was extremely troublesome and troublesome. However, since the packed column was used, the separation was poor, and high sensitivity and high resolution analysis could not be expected.

Therefore, a system has been proposed in which composition analysis of hydrocarbons in automobile exhaust gas can be easily measured with good operability by using a flow path structure in which a packed column and a capillary column are combined. ． p. It is possible to analyze up to m orders.

[0004]

However, when a capillary column capable of highly separating hydrocarbons is used, it is necessary to collect a large amount of sample with a sampling valve because the amount of the target component is very small. In that case, a large amount of samples cannot be collected due to the configuration that the whole is installed in the oven.

Further, in order to inject the entire amount of the sample into the capillary column, it is necessary to narrow the sample band, but this step cannot be adopted due to the constitution. Further, the conventional cryofocus cools the entire oven of the gas chromatograph with liquefied carbon dioxide gas, and there is a problem that the separation of low boiling point components is poor.

[0006]

Therefore, in the present invention,
The sampling valve allows a large amount of sample to be collected, and the sample band can be narrowed so that the entire amount of the sample can be injected into the capillary column. p. b to p. p. It is designed to enable analysis up to t, two sampling valves are installed in the valve oven, the first sampling valve can communicate with the packed column in the gas chromatograph, and the second sampling valve is A precolumn and a cold trap, characterized by being connected to a capillary column in a gas chromatograph via a thermal desorption cold trap injector concentrating and introducing device provided with an outlet through a solenoid valve,
Further, the carrier inflow portion provided in the second sampling valve is characterized in that it can communicate between the precolumn and the cold trap of the thermal desorption cold trap injector concentration introducing device.

[0007]

The present invention will be described in detail below with reference to an embodiment shown in the drawings. Reference numeral 1 is a first sampling valve, and a sample loop 17 is provided between the through hole 11 and the through hole 14. A helium supply unit 18 is connected to the through hole 12. A sample supply unit 19 is communicated with the through hole 15.

A second sampling valve 2 is provided with a sample loop 3 between a through hole 21 and a through hole 24 of the second sampling valve.
2, an outlet 4 is provided, a through hole 28 is provided with a helium supply part 29,
A discharge port 31, through a needle valve 30, through the through hole 26,
Hole 25 pre-column 5, the pre-column in the through-hole 27 5
The cold trap 6 and the cold trap 6 communicate with each other.

The pre-column 5 is under the condition of thermal desorption, cold trap injector (hereinafter referred to as TCT), and has a desired packing material such as OV-101 coating. The cold trap 6 has a plotting column 62 that is detachably installed in the cooling and heating device 61, which is changed depending on the target component.
The injector has a TCT, is a splitless injector, and the plot column 62 is a molecular sieve, a polar plot, or the like to improve the efficiency of cryofocus.

Reference numeral 7 denotes a tee (three-way joint) provided in a communication passage 9 to the capillary column 8 and a needle valve 7
1. It is connected to the discharge port 73 via the electromagnetic valve 72.

The first sampling valve 1 and the second sampling valve 2 and their connecting parts are housed in a valve oven 40, and their temperatures can be controlled. The communication hole 13 of the first sampling valve 1 has a communication passage 41 and is connected to the packed column 44.
Is connected to the detector 42. Further, the capillary column 8 is connected to the detector 43. Both detectors 42, 43
The Hako uses an FID detector. A gas chromatograph 45 is constituted by the packed column 44, the detector 43, the capillary column 8, and the detector 42.

Next, the operation will be described. First, analysis of volatile organic substances in seawater and analysis of automobile exhaust gas will be described.

First, in the case of analysis of volatile hydrocarbons in seawater, a continuous degassing device is connected and the volatile organic compounds transferred from the device are sent to the sample supply section 19. or,
In the case of automobile exhaust gas, a constant volume sampling device is used to supply the sample to the sample supply unit 19.

At this time, the sample sent to the sample supply unit 19 is the through hole 15 and the through hole 1 of the first sampling valve 1.
4 and then first accumulated in the sample loop 17
Sent in the sampling valve 2, and is discharged from the discharge port 4 to accumulate samples into the sample loop 3.

Therefore, when the first sampling valve 1 is switched, the helium supplied from the helium supply part 12 enters the sample loop 17 through the through hole 12 and the through hole 11, and passes through the through hole 14 and the through hole 13. After that, the sample is sent to the packed column 44 through the communication passage 41. It is separated by the packed column 44 and detected by the FID detector 43. Only quantification of methane is performed on this analytical line. Other components have low concentrations and are difficult to use in low amounts. In the case of automobile exhaust gas analysis, use packed columns up to C ₃ .

On the other hand, the sample accumulated in the sample loop 3 due to the switching of the second sampling valve 2 by the helium sent from the helium supply unit 29 passes through the through hole 2
4 and 25 to reach the pre-column 5 of TCT.

However, a filler is provided in the collection tube, and high boiling point components other than the target component are collected in the pre-column 5 by setting the humidity and time depending on the type and filling amount. At this time, the electromagnetic valve 72 of the TCT is opened and the discharge port 73 is opened.
By discharging more, the flow rate is increased and the effect of sample transfer is enhanced. At this time, the TCT is previously cooled by liquefied carbon dioxide, liquid nitrogen, or air cooled at -100 ° C.

In this apparatus, the target components of C _{2 to} C ₅ are
The cold trap 6 is configured accordingly and the cryofocus is performed. It is preferable to analyze a high boiling point component of C ₆ or more by a separate device. In this device, the type of the packing material, the filling amount, the precolumn temperature, and the cryofocus time are set so as to prevent the precolumn 5 from passing through. For exhaust gas analysis of a motor vehicle and an object component to C ₄ -C _12.

Then, the second sampling valve 2 is switched and the solenoid valve 72 is closed. Cold trap 6 here
When heated rapidly, the helium gas reaches the cold trap 6 through the through holes 28 and 27, and the trapped components are fed into the gas chromatograph through the communication passage 9. The sample is separated by the capillary column 8 and then detected by the FID detector 42.

On the other hand, at the same time, helium gas is supplied to the precolumn 5.
Then, backflushing is performed, and the high boiling point component of C ₆ or more in the pre-column 5 is discharged from the discharge port 31 through the needle valve 30. In the case of exhaust gas analysis of automobiles, high boiling point components with C ₁₃ or higher are emitted.

By maintaining this state for a certain period of time,
The pre-column 5 is conditioned. If the sample is automobile exhaust gas, it can detect up to C ₁₂
If the sample is seawater, p is at C ₂ -C ₅ detection. p. b ~
p. p. It can be detected in t-order.

[0022]

According to the present invention as described above, two sampling valves are installed in the valve oven, the first sampling valve can communicate with the packed column in the gas chromatograph, and the second sampling valve is the pre-column. And a cold trap, which is connected to the capillary column in the gas chromatograph through a thermal desorption cold trap injector concentration / introduction device having a discharge port via a solenoid valve, and a carrier inflow part provided in the second sampling valve. Since the thermal desorption cold trap injector concentrator / introducer can be connected between the precolumn and cold trap, the improved TCT concentrator / introducer can backflush high boiling point components other than the target component, and also to the capillary column. Accounts if possible the total amount of injection, high sensitivity,
High resolution analysis was possible.

By the cryofocus in the cold trap and the precolumn, the low-boiling point component is extremely well separated as compared with the conventional cooling of the entire oven of a gas chromatograph. Further, for example, high boiling point components of C ₆ or higher can be cut off, so that the main column of the capillary column can be protected and the analysis time can be shortened. In addition, since the pre-column serves as a backflush flow path, conditioning of the pre-column is automatically performed, which is a significant practical effect.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an embodiment of the present invention.

[Explanation of Codes] 1 First sampling valve 2 Second sampling valve 3 Sample loop 5 Pre-column 6 Cold trap 7 Tee (3-way joint) 8 Capillary column

Claims (2)

[Claims] 1. Two sampling valves are installed in a valve oven, the first sampling valve can communicate with a packed column in a gas chromatograph, and the second sampling valve consists of a precolumn and a cold trap, and a solenoid valve is provided. A continuous automatic volatile hydrocarbon analyzer characterized by being connected to a capillary column in a gas chromatograph via a thermal desorption cold trap injector concentrating and introducing device provided with a discharge port. 2. The carrier inflow portion provided in the second sampling valve can communicate between the precolumn and the cold trap of the thermal desorption cold trap injector concentration introducing device.
A continuous automatic analyzer for volatile hydrocarbons described in 1.