JP2001208737A - Gas chromatograph device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a vaporized sample from diffusing and being discharged from a purge channel when pressure is raised by the injection of the sample. SOLUTION: A control valve 12 is controlled so that a detection value P1 of a first pressure sensor 13 may become a set pressure at the time of a stationary state before the injection of a sample. As a pressure difference ΔP (=P2-P1) from a detection value P2 of a second pressure sensor 14 via a flow quantity resistance 11 is reduced when the gas pressure inside a sample vaporizing chamber 1 is suddenly increased after the injection of a sample, switching is performed to control the control valve 12 so as to maintain the pressure difference ΔP at a predetermined value when the pressure difference ΔP becomes less than the predetermined value. By this constitution, it is possible to continue to supply a predetermined quantity of flow of a carrier gas larger than the quantity of purge flow for the sample vaporizing chamber 1 and to prevent the vaporized sample from diffusing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas chromatograph, and more particularly, to a sample introduction section including a sample vaporizing chamber for vaporizing a liquid sample in a gas chromatograph.

[0002]

2. Description of the Related Art Generally, a gas chromatograph has a structure in which a liquid sample is injected into a sample vaporizing chamber provided at a column inlet, and the vaporized sample is loaded on a carrier gas and sent into the column. As a method for controlling and reducing the amount of the sample to be introduced into the column, a so-called split introduction method is used. In a gas chromatograph apparatus that performs split introduction, a carrier gas flow path for introducing a carrier gas into a sample vaporization chamber, a purge flow path for discharging an undesirable component generated by a silicon rubber septum to the outside, and A split flow path for discharging an excess vaporized sample to the outside together with the carrier gas is connected.

[0003] In such a device, two control systems, a constant pressure control system (also referred to as an inlet pressure control system) and a back pressure control system, are used to allow a carrier gas having a substantially constant flow rate to flow through the column. The constant pressure control method is a method in which a pressure control valve is provided in a carrier gas flow path and the opening of the pressure control valve is controlled so as to maintain a constant supply pressure of the carrier gas at the inlet of the sample vaporization chamber. On the other hand, in the back pressure control system, a mass flow controller (flow rate controller) is provided in the carrier gas flow path to introduce a constant flow rate of the carrier gas into the sample vaporization chamber, while a pressure control valve is provided in the split flow path to evaporate the sample. This is a method of controlling the pressure regulating valve so as to keep the pressure at the outlet of the chamber (the split flow path connection part) constant.

[0004]

When a liquid sample is injected into a sample vaporization chamber during gas chromatographic analysis, the volume of the injected sample rapidly expands due to vaporization. Therefore, the pressure in the sample vaporization chamber rapidly increases.
In the case of the constant pressure control method, when the inlet pressure suddenly increases, the pressure control valve is closed, so that the supply of the carrier gas to the sample vaporization chamber is temporarily stopped. Then, the vaporized sample is easily diffused in the sample vaporization chamber, and flows into the carrier gas channel and the purge channel. Therefore, a part of the vaporized sample to be sent to the column escapes to the outside through the purge channel,
Alternatively, it is carried to the column with a time delay. As a result, there is a problem that the accuracy of the quantitative analysis is reduced.

On the other hand, in the back pressure control method, when the pressure in the sample vaporization chamber rises sharply due to the vaporization of the injected sample, the pressure control valve is opened to allow the gas in the sample vaporization chamber to pass through the split flow path to the outside. Attempts to lower the pressure in the sample vaporization chamber by allowing it to escape. As a result, the split ratio temporarily changes, and the ratio of the sample introduced into the column decreases. As a result, there is a problem that the accuracy of the analysis is reduced.

That is, the conventional gas chromatograph apparatus has a problem that the accuracy of the quantitative analysis is reduced due to the diffusion of the vaporized sample at the time of sample injection. The present invention has been made to solve such a problem, and an object of the present invention is to provide a gas chromatograph capable of reducing the influence of a pressure increase during sample vaporization and improving the accuracy of quantitative analysis. An object of the present invention is to provide a chromatography apparatus.

[0007]

In order to solve the above-mentioned problems, a gas chromatograph according to the present invention adjusts the flow rate of a carrier gas according to the pressure at the inlet of the carrier gas into a sample vaporization chamber. Although it is based on the constant pressure control method, even if the gas pressure in the sample vaporization chamber increases immediately after sample injection, at least a certain amount of carrier gas can be continuously supplied to the sample vaporization chamber. It is.

That is, in the first gas chromatograph apparatus according to the present invention, a liquid sample is injected and vaporized into a sample vaporization chamber provided at a column inlet, and the vaporized sample is loaded on a carrier gas flow and introduced into the column. In the chromatography apparatus, a) a carrier gas flow path for supplying a carrier gas to the sample vaporization chamber, b) a flow resistance disposed on the carrier gas flow path, and c) a carrier gas upstream of the flow resistance. A regulating valve disposed on the flow path; d) a first pressure sensor for detecting a pressure on the outlet side of the flow resistance; and e) a second pressure sensor for detecting a pressure on the inlet side of the flow resistance. F) in a steady state, the control valve is controlled based on the detection value of the first pressure sensor, and after the sample is injected, the detection value of the second pressure sensor, or the detection of both the first and second pressure sensors. The control valve is controlled based on the value. It is characterized by comprising control means for, the.

In a second gas chromatograph apparatus according to the present invention, a liquid sample is injected into a sample vaporizing chamber provided at a column inlet and vaporized, and the vaporized sample is loaded on a carrier gas flow and introduced into the column. A first carrier gas flow path having a control valve for adjusting a flow rate in accordance with a pressure on the sample vaporization chamber side as a carrier gas flow path for supplying a carrier gas to the sample vaporization chamber; And a second carrier gas flow path having a flow rate adjusting means for flowing the carrier gas. After the sample is injected, the carrier gas is supplied to the sample vaporizing chamber through the second carrier gas flow path regardless of the opening degree of the control valve. It is characterized in that it is supplied.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an embodiment of a first gas chromatograph of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of a main part of the gas chromatograph device according to the present embodiment, centering on a sample vaporization chamber.

A septum purge flow path 6, a split flow path 7, and a carrier gas flow path 8 are connected to a sample vaporization chamber 1 having a hollow interior, and a septum 4 made of silicon rubber is provided at the head opening. It is inserted. A cylindrical glass insert 5 is fitted inside the sample vaporization chamber 1,
Column 2 is a glass insert 5 from the bottom of sample vaporization chamber 1
Is inserted up to the inside.

Needle valves 9 and 10 are provided in the septum purge channel 6 and the split channel 7, respectively.
The flow resistance can be adjusted appropriately. A first pressure sensor 13, a flow resistance 11, a second pressure sensor 14, and a control valve 12 are provided in the carrier gas flow path 8 from the downstream side, and the control unit 15 controls the detection gas pressure of the first pressure sensor 13. The opening of the control valve 12 is controlled according to P1 and the detected gas pressure P2 of the second pressure sensor 14. First pressure sensor 13
Since there is almost no gas resistance between the sample vaporization chamber 1 and the sample vaporization chamber 1, the detected gas pressure P1 can be considered to be substantially the same as the gas pressure inside the sample vaporization chamber 1. If necessary, the septum purge flow path 6 and the split flow path 7 may be provided with an electromagnetic on-off valve.

In the above configuration, when performing gas chromatographic analysis, a liquid sample is injected into the sample vaporizing chamber 1 through the septum 4 by the sample injector 3. The injected sample is vaporized almost instantaneously in the sample vaporization chamber 1 heated to an appropriate temperature, and is carried into the column 2 by a carrier gas flow. Then, components are separated in the process of passing through the column 2.

The control which is a characteristic of the gas chromatograph will be described with reference to the flowchart of FIG. Also,
FIG. 4 is a diagram showing an example of a change in gas pressure in the sample vaporization chamber 1 before and after the sample injection at this time. In a steady state before the liquid sample is injected into the sample vaporization chamber 1, the control unit 15 monitors the gas pressure P1 detected by the first pressure sensor 13, and operates the control valve 12 so that the gas pressure P1 becomes the set pressure Pc. It controls (step S1). As a result, a substantially constant flow rate of the carrier gas is supplied to the sample vaporization chamber 1 through the carrier gas flow path 8. At this time, a pressure difference ΔP (= P2−P1) corresponding to the flow resistance value and the flow rate is provided at both ends of the flow resistance 11.
Has occurred.

When a liquid sample is injected into the sample vaporization chamber 1 and the sample is vaporized (step S2), the gas pressure in the sample vaporization chamber 1 sharply increases as shown in FIG. , The detected gas pressure P1 sharply increases. On the other hand, since the detected gas pressure P2 of the second pressure sensor 14 connected to the sample vaporization chamber 1 via the flow resistance 11 does not follow the increase of the gas pressure so much, the pressure difference ΔP decreases or becomes negative in some cases. . Therefore, the control unit 15 monitors the pressure difference ΔP after the sample injection, and determines that the pressure difference ΔP is equal to the predetermined value Pa.
When the pressure becomes below (“Y” in step S3), the detected gas pressure P
The control using only 1 is stopped, and the control valve 12 is controlled so that the pressure difference ΔP becomes the predetermined value Pa (step S4).

That is, if the control using only the detected gas pressure P1 is continued, in the worst case, the control valve 12 is closed due to the sudden rise of the detected gas pressure P1 and the supply of the carrier gas is completely completed. May stop. When the carrier gas stops flowing, as shown in FIG. 2B, the vaporized sample may be diffused upward in the sample vaporization chamber 1, flow into the septum purge flow path 6, and may be discharged to the outside. . On the other hand, when the pressure difference ΔP is switched to control to maintain the pressure difference ΔP at a predetermined value, the pressure difference ΔP and the flow resistance 11
, The carrier gas having a substantially constant flow rate determined by the resistance value can be continuously supplied to the sample vaporization chamber 1. Therefore, FIG.
As shown in (a), the sample vaporized in the sample vaporization chamber 1 is suppressed from diffusing upward by the carrier gas flow, and flows to the column 2 and the split channel 7 according to the determined split ratio. Further, it is preferable that the minimum flow rate of the carrier gas is set to be equal to or higher than the gas flow rate discharged through the septum purge passage 6. Then, since the carrier gas preferentially flows into the septum purge flow path 6, it is possible to more effectively prevent the vaporized sample from flowing into the septum purge flow path 6 and being discharged.

As described above, after the gas pressure rises sharply and the control in step S4 is performed, as shown in FIG. 4, the gas pressure in the sample vaporization chamber 1, ie, the detected gas pressure P1, gradually decreases. When the pressure returns to the set pressure Pc ("Y" in step S5), the control unit 15 controls the control valve 12 again so that the detected gas pressure P1 becomes the set pressure Pc (step S6). For example, if the pressure difference ΔP does not become Pa or less immediately after sample injection, such as when the injected liquid sample is extremely small, the process proceeds from step S3 to step S6, and control continues so that the detected gas pressure P1 becomes the set pressure Pc. It is done.

Next, a specific example of the above control will be described with reference to numerical values. Now, the purge flow rate flowing to the septum purge flow path 6 is 2 mL / min, the split flow rate flowing to the split flow path 7 is 47 mL / min, and the flow rate flowing to the column 2 is 1 mL / min.
In this case, the flow rate of the carrier gas to be supplied to the sample vaporizing chamber 1 through the carrier gas flow path 8 is 50 mL / min. At this time, the gas pressure in the sample vaporization chamber 1 (that is, the set pressure Pc) is assumed to be 100 kPa, and the pressure difference ΔP is assumed to be 10 kPa. Then, of the pressure difference ΔP, the contribution of the purge flow rate, that is, the pressure difference between both ends of the flow resistance 11 required to secure the purge flow rate is 1
0 × 2/50 = 0.4 kPa is obtained. Therefore, the determination threshold Pa of ΔP is 1 kPa, which is larger than 0.4 kPa.
It is determined.

Before the sample injection, the control unit 15 controls the detected gas pressure P1.
Control valve 12 such that the set pressure Pc = 100 kPa.
Is controlling. Thereby, the carrier gas is supplied to the sample vaporizing chamber 1 through the carrier gas flow path 8 at a flow rate of 50 mL / min, and the purge flow rate becomes 2 mL / min. The detected gas pressure P1 sharply rises due to the sample injection, and the pressure difference ΔP becomes 1
When the pressure becomes equal to or less than kPa, the control unit 15 controls the control valve 12 so that ΔP becomes 1 kPa regardless of the value of P1. Accordingly, a carrier gas having a substantially constant flow rate larger than the predetermined purge flow rate of 2 mL / min is surely supplied to the sample vaporization chamber 1, and the diffusion of the vaporized sample is suppressed by the carrier gas as described above.

The curve shown by the dotted line in FIG. 4 is an example in the case where the gas pressure is controlled by the conventional constant pressure control method. In the gas chromatograph according to the present invention, the carrier gas is surely provided immediately after the sample injection. This indicates that the gas pressure in the sample vaporization chamber 1 itself becomes higher than in the past by continuing to supply the gas.

FIG. 5 is a block diagram showing an embodiment of the second gas chromatograph apparatus of the present invention. In this embodiment, the carrier gas main flow path 81 provided with the control valve 12 and the carrier gas sub flow path 82 provided with the mass flow controller 16 are arranged in parallel, and the minimum flow rate (at least the purge flow rate) is passed through the carrier gas sub flow path 82. The above carrier gas is supplied to the sample vaporization chamber 1. Thereby, even if the control valve 12 is closed immediately after sample injection, the carrier gas sub-flow path 82
A constant flow rate of carrier gas can be introduced into the sample vaporization chamber 1 through

It should be noted that each of the above embodiments is merely an example, and it is apparent that changes and modifications can be made as appropriate within the scope of the present invention.

[0023]

According to the first and second gas chromatograph apparatuses according to the present invention, even if the pressure rises immediately after the liquid sample is injected into the sample vaporizing chamber, the carrier gas is supplied to the sample vaporizing chamber. Since the supply is continued, the diffusion of the vaporized sample is suppressed, and the vaporized sample in a predetermined amount or in an amount corresponding to the predetermined split ratio can be reliably sent to the column. For this reason,
Performs high-precision quantitative analysis and improves reproducibility.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a main part mainly of a sample vaporization chamber in an embodiment of a first gas chromatograph device of the present invention.

FIG. 2 is a schematic diagram showing the behavior of a vaporized sample in a first gas chromatograph device of the present invention and a conventional device.

FIG. 3 is a flowchart of gas pressure control in the gas chromatograph device of the present embodiment.

FIG. 4 is a diagram showing a change in gas pressure in a sample vaporization chamber before and after sample injection.

FIG. 5 is a configuration diagram of a main part in an embodiment of the second gas chromatograph device of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Sample vaporization chamber 2 ... Column 6 ... Septum purge flow path 7 ... Split flow path 8 ... Carrier gas flow path 9, 10 ... Needle valve 11 ... Flow resistance 12 ... Control valve 13 ... 1st pressure sensor 14 ... 2nd pressure Sensor 15 Control part 16 Mass flow controller 81 Carrier gas main flow path 82 Carrier gas sub flow path

Claims (2)

[Claims] 1. A gas chromatograph device for injecting and vaporizing a liquid sample into a sample vaporization chamber provided at a column inlet, placing the vaporized sample on a carrier gas flow and introducing the sample into a column, comprising the steps of: A carrier gas flow path for supplying gas, b) a flow resistance disposed on the carrier gas flow path, c) a control valve disposed on a carrier gas flow path upstream of the flow resistance, d. A) a first pressure sensor for detecting the pressure on the outlet side of the flow resistor; e) a second pressure sensor for detecting the pressure on the inlet side of the flow resistor; and f) a first pressure sensor in the steady state. Control means for controlling the control valve based on the detected value, and controlling the control valve based on the detected value of the second pressure sensor or the detected values of both the first and second pressure sensors after sample injection. And a gask comprising: Chromatograph apparatus. 2. A gas chromatograph device for injecting and vaporizing a liquid sample into a sample vaporization chamber provided at a column inlet, placing the vaporized sample on a carrier gas flow and introducing the vaporized sample into a column, wherein a carrier gas is introduced into the sample vaporization chamber. As a carrier gas flow path to be supplied, a first carrier gas flow path having a control valve for adjusting a flow rate according to the pressure on the sample vaporization chamber side, and a flow rate control means having a flow rate adjusting means for flowing a predetermined constant flow rate of a carrier gas. A second carrier gas flow path, wherein after the sample is injected, a carrier gas is supplied to the sample vaporization chamber through the second carrier gas flow path regardless of the degree of opening of the control valve. apparatus.