JPH06331613A - Gaschromatograph - Google Patents

Abstract

PURPOSE:To stabilize a base line of a chromatogram by making a supply pressure of a carrier gas constant through control of a pressure reducing valve with a detection pressure of a pressure detection part arranged immediately before a second column. CONSTITUTION:In the case of a back flash, a flow resistance of a first column 47a does not fully equal to that of a resistance column 47c and there becomes a state that no detection is found at a concentration detection part 48, that is, a base line is changed. Thus, a pressure detection part 3 is provided immediately before a second column 47b so as to detect a supply pressure of a secondary side carrier gas of a pressure reducing valve 1, and a CPU 11 controls a solenoid valve driving part 12 with its detection signal so that a pressure of a carrier gas to be led to the column 47c during analyzing operation is made constant with a set value. Thus, even if a flow resistance of the column 47a is different from that of the column 47c, a flow rate of the carrier gas to be supplied to the column 47b is made constant whether a communication source of the column 48b is either the column 47a or 47c. That is, even if a flow rate resistance of the column 47a is different from that of the 47c, the base line is not fluctuated before and after the back flash.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
Gas chromatograph with two columns.

[0002]

2. Description of the Related Art A gas chromatograph is a useful device for analyzing liquids and gases composed of various organic compounds. In a gas chromatograph, a plurality of substances dissolved in a liquid to be analyzed can be separated and their amounts can be detected respectively, so that qualitative analysis and quantitative analysis can be performed simultaneously.
In a gas chromatograph, a solution to be analyzed is heated to form a gas, and the gas is passed through a column (fixed bed) for separating compounds having different structures by a carrier gas. A plurality of compounds dissolved in the gasified solution to be analyzed are separated by being carried by the carrier gas and passing through the column, and their respective amounts are separated by the concentration detection unit arranged at the outlet of the column. Is measured.

FIG. 2 is a block diagram showing the structure of a conventional gas chromatograph. In FIG. 2, 1 is a pressure reducing valve for adjusting the pressure of the carrier gas, 2a is a step-up solenoid valve for adjusting the operation of the pressure reducing valve 1, 2b is a step-down solenoid valve for also adjusting the operation of the pressure reducing valve 1, Reference numeral 3a is a pressure detection unit that detects the pressure of the carrier gas on the secondary side of the pressure reducing valve 1.

Reference numeral 4 denotes an analyzer valve, which includes a carrier gas introducing section 44, a sample injecting section 45, a measuring tube 46 for measuring and holding a predetermined amount of the sample in the sample injecting section 45, and an analysis target. A first column 47a for separating substances,
The second column 47b, the resistance column 47c, the first and second columns
It is composed of a concentration detector 48 for detecting the amount of each substance separated in the columns 47a and 47b, and an exhaust unit 49 for exhausting the carrier gas and sample gas that have passed through the analyzer valve 4. Further, 8 is a valve drive electromagnetic valve for controlling gas for driving the analyzer valve, 9 is an A / D converter for A / D converting the signal from the pressure detection unit 3a, 1
Reference numeral 1a is a CPU, and 12 is a solenoid valve drive unit that outputs drive signals for the pressure increasing solenoid valve 2a, the pressure reducing solenoid valve 2b, and the valve drive electromagnetic valve 8.

The analyzer valve 4 switches the connection of each flow path according to the pressure of the carrier gas whose on / off is controlled by the valve driving solenoid valve 8. First, when the valve drive solenoid valve 8 is off, as shown in FIG.
5, the measuring pipe 46 and the discharge part 49 communicate with each other, while the carrier gas introducing part 44, the first column 47a and the discharge part 49 communicate with each other, and the carrier gas introducing part 44 and the resistance column 47.
The c, the second column 47b, the concentration detecting section 48, and the discharging section 49 communicate with each other. Next, when the valve drive solenoid valve 8 is on, as shown in FIG. 3B, the carrier gas introducing part 44, the measuring pipe 46, the first column 47a, and the second column 4 are inserted.
7b, the concentration detection unit 48, and the discharge unit 49 communicate with each other, the carrier gas introduction unit 44, the resistance column 47c, and the discharge unit 49 communicate with each other, and the sample injection unit 45 and the discharge unit 49 communicate with each other.

The operation of this gas chromatograph will be described below. First, when the analysis is started, the valve drive electromagnetic valve 8 is off, and the sample gas introduced from the sample injection part 45 into the analyzer valve 4 is discharged from the discharge part 49 through the measuring pipe 46. On the other hand, at this time, the pressure reducing valve 1 and the solenoid valves 2a, 2b
The carrier gas adjusted to a constant pressure by the carrier gas is introduced into the analyzer valve 4 from the carrier gas introduction unit 44, passes through the first column 47a and is discharged through the discharge unit 49, and after passing through the second column 47b. , Concentration detector 48
And is discharged from the discharge section 49.
Here, the solenoid valves 2a and 2b are controlled by the CPU 11a and the potential valve drive unit 12 using the pressure detected by the pressure detection unit 3a. That is, the pressure on the secondary side of the pressure reducing valve 1 is controlled so that the pressure detected by the pressure detection unit 3a becomes the set pressure.

Next, when the valve drive solenoid valve 8 is turned on, the analyzer valve 4 switches its connection as described above. At this time, the sample gas introduced from the sample introducing unit 45 and passing through the measuring pipe 46 has the communication source of the measuring pipe 46 as the carrier gas introducing unit 44 and the communication destination as the first column 4
7a, the predetermined amount is measured by the measuring pipe 36, and only the amount is carried to the carrier gas and moved to the first column 47a. The sample gas is separated to some extent by the components contained by passing through the first column 47a,
It moves to the second column 47b where it is completely separated. Then, in the sample gas in which the components contained in the second column 47b are completely separated, the separated components sequentially pass through the concentration detection unit 48, and the respective amounts are detected.

By the way, when the valve driving electromagnetic valve 8 is turned off again after the sample gas has passed through the first column 47a to some extent, the carrier gas introducing portion 44 and the resistance column 4 are provided.
7c, the second column 47b, and the concentration detector 48 are in communication with each other. On the other hand, in the first column 47a, the communication source is the carrier gas introduction section 44, and the communication destination is the discharge section 49.
The flow direction of the carrier gas in the column 47a changes.
As a result, the components of the sample gas still remaining in the first column 47a at this point are discharged from the discharge section 49 so as to be pushed back by the carrier gas.

On the other hand, the components of the sample gas that have passed through the first column 47a and have reached the second column 47b are
It is carried by the carrier gas that has passed through the resistance column 47c, moves to the second column 47b, and is completely separated by this second column 47b. Then, in the sample gas in which the contained components are completely separated by the second column 47b, the separated components each independently pass through the concentration detector 48, and the respective amounts are detected. That is, by turning off the valve driving electromagnetic valve 8 at a predetermined time while the sample gas is passing through the first column 47a, only a desired component in the sample gas can be analyzed.

The gas chromatograph separates the components constituting the sample gas by passing the sample gas through the column. This utilizes the difference in the ease with which the components of this sample gas pass through the column. Among the constituents of the sample gas, the constituents having a light mass easily pass through the column and quickly pass through the column. On the other hand, heavy components are difficult to pass through the column and do not easily come out of the column. In addition, a heavy component that is difficult to pass through the column often accelerates the deterioration of the column. Therefore, it is desirable to prevent the components having a large mass from passing through the column when not being analyzed.

The first column 47a in the gas chromatograph of FIG. 2 is for selecting the component to be analyzed in the sample gas, and the second column is for separating the sample gas passing through for actual analysis. is there. The resistance column 47c has the same carrier gas passage resistance as that of the first column 47a, and always keeps the carrier gas carrying speed for carrying the sample gas constant.
It is possible to prevent the second column 47b from deteriorating much by preventing heavy components that have passed through the first column 47a and separated and do not need to be analyzed from going to the second column. .

As described above, the carrier gas introducing portion 44 is provided when the valve drive solenoid valve 8 is on and when it is off.
The flow path from the first column 47a to the concentration detection unit 48 changes, and in particular, the flow path to the second column 47c may or may not pass through the first column 47a. When the valve drive solenoid valve 8 is on, the communication destination of the first column 47a is the second column, and when the valve drive solenoid valve 8 is off, the first column 47a.
The communication destination of is the discharge unit 49. This valve drive solenoid valve 8
Of the components separated in the first column 47a, it is possible to prevent introducing into the second column 47b a heavy component that does not need to be analyzed and deteriorates the second column (backflush). .

Here, in the above-mentioned case, when the carrier gas introduced from the carrier gas introducing section 44 changes in the flow rate of the carrier gas depending on whether the carrier gas passes through the first column 47a or not, the concentration detecting section 48 is provided. Is not detected, that is, the baseline changes. Therefore, the carrier gas introduced from the carrier gas introduction part 44 is first
When it does not pass through the column 47a, it passes through the resistance column 47c so that its flow rate does not change.

[0014]

Since the conventional configuration is as described above, there is a problem in that the flow resistances of the first column and the resistance column are not completely equal and the baseline of the chromatogram is not stable. there were. In a gas chromatograph column, a pipe made of steel or the like is packed with a fixed layer, which is used in a coil shape. The flow resistance of the column changes depending on the filling state of the fixed bed, the state of forming into a coil, and the like. Further, it is difficult to make the fixed state of the fixed layer and the state of forming a coil into a completely uniform state. In addition, since the resistance column is only for obtaining the flow resistance, it is only packed with glass beads etc., and it is very difficult to make the flow resistance perfectly match the column filled with the fixed bed. is there.

The present invention has been made to solve the above-mentioned problems, and a baseline of a chromatogram obtained in a gas chromatograph in which backflushing is performed by using two columns connected in series. The purpose is to ensure that does not change.

[0016]

A gas chromatograph according to the present invention comprises a first column for separating a gas to be measured composed of a plurality of components and carried by a carrier gas into respective components, and a first column. A second column that separates the gas to be measured that has passed through the column into each component, a concentration detection unit that communicates with the second column to detect the concentration of the gas that has passed through the second column, and the supply of carrier gas A pressure reducing valve that keeps the pressure constant, a solenoid valve that controls the operation of the pressure reducing valve, a pressure detection unit that is arranged immediately before the second column and that detects the pressure,
Control means for controlling the operation of the solenoid valve according to the pressure detected by the pressure detection means, a first flow path through which the pressure reducing valve communicates with the first column and the second column, and the pressure reducing valve and the second column And a flow path switching means for switching a second flow path communicating with each other without passing through the first column.

[0017]

The flow rate of the gas introduced into the second column is always kept constant.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram showing the configuration of a gas chromatograph according to one embodiment of the present invention. In the figure, 3 is a pressure detector provided immediately before the second column 47b, and 11
Is a CPU that controls the solenoid valve drive unit 12 based on a signal from the pressure detection unit 3, and is otherwise similar to FIG. In the gas chromatograph of this embodiment, the supply pressure amount of the carrier gas on the secondary side of the pressure reducing valve 1 is different from that of the conventional example as shown in FIG.
As shown in, the pressure detected by the pressure detection unit 3 installed immediately before the second column 47b is controlled to be the set pressure.

That is, in this gas chromatograph,
During the analysis operation, the pressure of the gas introduced into the second column 47b is controlled to be constant at the set value.
Therefore, even if the flow resistances of the first column 47a and the resistance column 47c are different, the second column 47b is supplied to the second column 47b depending on whether the communication source is the first column 47a or the resistance column 47c. The carrier gas flow rate is constant and does not change. That is, even if the flow resistances of the first column 47a and the resistance column 47c are different, the baseline does not change before and after backflushing.

In the above embodiment, the resistance column 47c is provided at the communication source of the second column 47a when the valve drive solenoid valve 8 is off, but the invention is not limited to this. The communication source of the second column 47a may be the carrier gas supply introduction part 44 when the resistance drive column 47c is not provided and the valve drive solenoid valve 8 is off.

[0021]

As described above, according to the present invention, in a gas chromatograph in which backflushing is performed using two columns connected in series, there is an effect that the baseline does not fluctuate before and after backflushing. is there. Therefore, according to the gas chromatograph of the present invention, analysis results with high accuracy and high reproducibility can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of a gas chromatograph according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a configuration of a conventional gas chromatograph.

FIG. 3 is a channel diagram showing a carrier gas channel of a gas chromatograph.

[Explanation of symbols]

 1 Pressure reducing valve 2a Step-up solenoid valve 2b Step-down solenoid valve 3 Pressure detecting unit 4 Analyzer valve 8 Valve driving solenoid valve 9 A / D converter 11 CPU 12 Solenoid valve driving unit 44 Carrier gas introducing unit 45 Sample injection unit 46 Measuring pipe 47a 1st column 47b 2nd column 47c Resistance column 48 Concentration detection part 49 Discharge part

Claims (1)

[Claims] 1. A first column for separating a gas to be measured composed of a plurality of components and carried by a carrier gas into respective components, and a gas to be measured passed through the first column. A second column for separating the components, a concentration detecting means for communicating with the second column to detect the concentration of the gas passing through the second column, and a pressure reducing valve for keeping the supply pressure of the carrier gas constant. An electromagnetic valve that controls the operation of the pressure reducing valve; a pressure detection unit that is arranged immediately before the second column to detect the pressure; and an operation of the electromagnetic valve that is controlled by the pressure detected by the pressure detection unit. Control means, a flow path through which the pressure reducing valve communicates with the first column and the second column, and a flow path through which the pressure reducing valve communicates with the second column without passing through the first column And a flow path switching means for switching between Gas chromatograph, characterized in that it comprises.