JP2508749B2 - Gas chromatograph - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a gas chromatograph capable of easily obtaining a split ratio of a sample introduced in a capillary column gas chromatograph for introducing a sample in a split system.

(Prior art) In split-type sample introduction, to determine the split ratio of the introduced sample, the flow rate V1 of the carrier gas flowing through the capillary column and the flow rate V2 of the carrier gas discharged from the split-out flow path are calculated as V1 / V2. Was calculated as the split ratio.

(Problems to be Solved by the Invention) Usually, the gas flow rate is measured by a manual method using a soap film flow meter or the like. In this case, in order to obtain the gas flow rate V1 flowing through the capillary column, it is difficult to measure the flow rate precisely because the flow rate is small, and it is necessary to disconnect the column outlet side to remove the makeup gas. Is not easy.

Also, the measured values of these gas flow rates V1 and V2 show the gas flow rate of each flow path when the carrier gas is split in a steady state. However, during the actual analysis, the volume of the sample (gas / liquid) introduced into the sample vaporization chamber (sample introduction part) rapidly increases due to the high temperature state of the vaporization chamber, which causes a temporary fluctuation in the flow rate.

The split ratio is a numerical value showing the ratio of the sample introduced into the column among the introduced samples, and the split ratio in the unsteady state at the time of introducing the beverage described above is the true split ratio required for the calculation of analytical measurement values. The split ratio obtained from the gas flow rate in the steady state of the conventional method had a problem with its reliability.

The present invention provides a gas chromatograph capable of obtaining a split ratio from a measurement value of a known amount of standard sample gas by a detector, eliminating manual measurement, and easily obtaining a highly reliable split ratio. It is an object of the present invention to provide a gas chromatograph that enables automation of split ratio measurement as needed.

(Means for Solving Problems) The present invention provides a standard column gas introduction port in the make-up gas channel and a split-out separately from the detector in the measurement channel in a capillary column gas chromatograph for introducing a sample in a split system. The channel is also provided with a detector.

The detectors installed in the split-out flow path are thermal conductivity detector (TCD), hydrogen flame ionization detector (FID), flame photometric detector (FFD), electron capture detector (ECD), thermal ionization detector (FTD), etc., and does not necessarily have to be the same type as the detector on the measurement flow path side.

(Operation) First, part of the known amount of standard sample gas introduced from the sample inlet of the measurement channel is introduced to the capillary column and detected by the detector of the same channel, and the area value (A1) is At the same time as the measurement, the rest of the standard sample gas passes through the split-out flow path and is detected by the detector provided in the same flow path, and the area value (A2) is measured. There is no difference in sensitivity between these two detectors. That is, when the same amount of standard sample gas shows the same response, the split ratio R is determined by R = A1 / A2. However, since a difference in sensitivity will inevitably occur between the two detectors due to the flow rate of the sample gas introduced into the detector, the processing of the detector, etc., this difference in sensitivity must be corrected. A standard sample gas inlet provided in the makeup gas flow path is used for this correction.

That is, the area values A1, A2 from the standard sample gas inlet
The same amount of standard sample gas used to measure
The area value (A0) is measured by detecting the entire amount of the detector in the measurement channel through the make-up gas channel.

When the sensitivity ratio of both detectors is X, A0 = A1 + XA2 holds, and X is calculated by X = (A0-A1) / A2. Therefore,
The split ratio R, which is the corrected sensitivity ratio between the detectors, is It can be obtained by the equation (1).

The sample inlet is normally kept at a high temperature, and the introduced standard sample gas expands rapidly, causing flow rate fluctuations and splitting in this state. That is, the area values A1, A
Since 2 indicates the amount of split in the unsteady state, it is possible to obtain a split ratio that matches the actual cost of introducing the sample.

(Example) FIG. 1 is a configuration diagram showing an example of a capillary column gas chromatograph of the present invention. Both detector 28 and detector 1 are FTDs. Helium gas 21 is introduced into the carrier gas flow path 23, and the flow rate thereof is determined by adjusting the pressure regulator 22. The flow rate of the capillary column 26 is about 1 to 5 ml / min, and the split ratio (usually 1/50 to 1/100) is adjusted by adjusting the needle valve 34 connected to the split out channel 32. On the other hand, the helium gas 29 is introduced into the makeup gas flow path 31, and the pressure regulator 30 is adjusted so that the flow rate thereof is 40 to 50 ml / min. In this state, a known amount of methane gas is first introduced as a standard sample gas from the sample introduction port 24. Capillary column with methane gas flow path branching section 25
26 and split-out channel 32. The methane gas that has entered the capillary column 26 reaches a detector 28, and the area value A1 is measured by the detector 28.

Methane gas is hardly retained in many types of capillary columns and gives a chromatogram with a sharp shape in the vicinity of the void volume, which is suitable for implementation of the apparatus of the present invention for which the area value is to be accurately measured. On the other hand, split-out flow path
The methane gas entering 32 reaches the detector 1 in the same flow path, and the area value 42 is measured by the detector 1.

The trap 33 provided in the split-out flow path 32 is
In order to prevent the needle valve 34 from being contaminated by sample components passing through the flow path during actual sample analysis, a molecular sieve is usually used to trap these components.
Since the methane gas does not mutually use adsorption and desorption for the molecular sieve, the detector 1 can accurately measure the amount of methane gas. Next, the same amount of methane gas as that at the time of the measurement is supplied from the standard sample gas inlet 2 to the makeup gas flow path 31.
Will be introduced. The standard sample gas inlet port 2 is composed of, for example, a box (a normal sample inlet port for pack drum cam) having a septum and a gas inlet / outlet port.

The introduced methane gas, together with the helium gas flow, passes through the makeup gas flow passage 31 and the makeup gas inlet 27 to the detector 28 of the measurement flow passage, and the detector 28 measures the area value A0. As a result, an accurate split ratio can be obtained by the above equation (1).

FIG. 2 is a constitutional view showing another embodiment of the capillary column gas chromatograph of the present invention. In the figure, 4 is a standard gas inlet, 5 and 8 are hexagonal switching valves (hereinafter referred to as valves A and B), and a carrier gas flow path is provided at a connection port of valve B.
23, the makeup gas flow path 31, and the outlets 6 and 7 of the valve A are connected. Carrier gas 21, makeup gas 29
Helium gas is used. Both detector 1 and detector 28 are FIDs. First, with the valve A in the solid line and the valve B in the solid line, the stop valve 11 is opened and the standard sample gas inlet 9 is opened.
A standard mixed gas of 1 to 0.1% methane and a helium balance is filled in the measuring pipe 3 (volume 0.5 to 1 ml). After this, when the valve A is switched to the broken line state, the measuring pipe 3
The standard mixed gas therein is introduced into the make-up gas passage 31, and the area value A0 is obtained by the detector 28.

Next, the valve A is set to the solid line state, and the measuring tube 3 is filled with the standard mixed gas again. Subsequently, when both the valve A and the valve B are set to the broken line state, the standard mixed gas in the measuring pipe 3 is introduced into the carrier gas flow path 23 and reaches the sample introduction port 24 together with the carrier gas. Here, the same rapid expansion as in the case of normal sample introduction is performed, the flow path branching portion 25 splits, and the part that has passed through the capillary column 26 and the remainder that has passed through the split-out flow passage 32 have their respective detectors 28, 1
Leading to. Then, the area value A1 is measured by the detector 28 and the area value A2 is measured by the detector 1, and the split ratio is obtained by the equation (1).

When the measurement of the area value for obtaining the split ratio is completed by the above operation, the stop valve 11 is closed and the normal analysis is performed with the valve A in the solid line and the valve B in the broken line.

In this example, the helium-balanced methane mixed gas is used as the standard mixed gas in order to prevent the baseline fluctuation when the area value A1 is measured.

Although an example of using helium as the carrier gas has been described, the implementation of the device of the present invention is not limited to this. For example, when hydrogen gas is used as the carrier gas and nitrogen gas is used as the makeup gas, methane standard mixed gas of hydrogen gas balance is used as the standard mixed gas.

FIG. 3 is a partial constitutional view showing still another embodiment of the capillary column gas chromatograph of the present invention. The split-out flow path 32 and the makeup gas flow path 31 are connected via a four-way switching valve 12. First, with the four-way switching valve 12 in the solid line state, a known amount of methane gas is introduced into the makeup gas flow path 31 from the standard sample gas introduction port 2 (not shown), and the area value A0 is measured by the FID detector 28. Next, the four-way switching valve 12 is in the state of a solid line, methane gas of a colleague is introduced from a sample inlet 24 (not shown), split, and the methane gas that has passed through the capillary column 26 reaches the FID detector 28, and the area value A1 is measured. It
Then, the four-way switching valve 12 is set to the broken line state, the same amount of methane gas is reintroduced from the sample introduction port 24 (not shown), the methane gas split in the split-out flow path 32 reaches the FID detector 28, and the area value is reached. A2 is measured.
Then, the split ratio is obtained by the above equation (1).
When the measurement of the area value for obtaining the split ratio is completed by the above operation, the four-way switching valve 12 is set to the solid line state, and the normal analysis is performed.

(Effects) According to the present invention, it is possible to realize a capillary column gas chromatograph which can easily determine the split ratio according to the actual condition at the time of sample introduction without depending on the manual measurement. It is also possible to automatically calculate the split ratio. Furthermore, when hydrogen gas is used as the carrier gas and FID is used as the detector, the hydrogen gas on the split-out flow path side is the FID installed in the same flow path.
It is converted into water vapor by the flame of and improves the safety during gas chromatographic analysis.

[Brief description of drawings]

1 and 2 are configuration diagrams showing an embodiment of the capillary column gas chromatograph of the present invention. FIG. 3 is a partial constitutional view showing another embodiment of the capillary column gas chromatograph of the present invention. 1, 28 …… Detector, 24 …… Sample inlet 2, 4 …… Standard sample gas inlet 25 …… Flow path branch 5,8 …… Hex-directional switching valve 31 …… Make-up gas flow path 12 …… Four-way switching valve 32 …… Split-out flow path

Claims (3)

(57) [Claims] 1. A measurement flow path comprising a carrier gas flow path, a sample introduction part, a capillary column and a detector, which are arranged in this order,
In a gas chromatograph having a split-out flow path branched from between the sample introduction part and the capillary column and a make-up gas flow path connected between the capillary column and the detector, a detector is provided in the split-out flow path. Along with mounting, a sample introduction part is provided in the make-up gas flow path, and a known amount of standard sample is first introduced from the sample introduction part of the measurement flow path and the detectors of the measurement flow path and the split-out flow path are used. Detect the amount of each sample,
Then, a known amount of standard sample is introduced from the makeup gas channel, and the total amount is detected by the detector of the measurement channel,
This value is used to calculate the sensitivity correction values for both detectors,
A gas chromatograph characterized in that a split ratio is obtained from the measured values of both the detectors based on the sensing correction value. 2. A carrier gas flow path, a make-up gas flow path, and a standard sample supply section are connected via a hexagonal switching valve having a measuring pipe, and a standard amount of a known sample is measured by switching the switching valve. The gas chromatograph according to claim 1, wherein the gas chromatograph is introduced into the flow passage and the makeup gas flow passage. 3. The make-up gas passage and the split-out passage are connected by a switching valve, and the detectors in the measurement passage and the split-out passage are shared by a single detector. The gas chromatograph according to claim 1 or 2.