A high pressure sampling device for gas chromatographic analysis

Abstract

The utility model discloses a high pressure sampling device for gas chromatography analysis, including sampling pipeline, sampling device, purging pipeline and cleaning pipeline, sampling pipeline includes the switching valve, sampling valve front pipeline, quantitative sampling valve and sampling valve rear pipeline that connect gradually, quantitative sampling valve is equipped with sampling cavity, first gas cavity, solvent cavity and second gas cavity, switching sampling device, purging pipeline and cleaning pipeline are connected through switching valve, sampling valve front pipeline and quantitative sampling valve respectively. The device can make quantitative solvent flow through quantitative sampling valve with sample after sample injection and inject simultaneously, thereby washes high boiling point component adhered in flow path into gasification chamber, thoroughly solves sample injection distortion problem, and through the design of pipeline and valve structure, sample injection and the solvent injection of following immediately can be realized by same valve action, and complicated valve system and program control and other cumbersome device are not needed.

Description

Technical Field

[0001] This utility model relates to the field of analytical chemistry technology, specifically to a high-pressure injection device for gas chromatography analysis. Background Technology

[0002] Chemical plants often require materials composed of multiple components as reaction media, typically containing both atmospheric pressure gaseous and liquid components. The gaseous components are liquefied by pressure within the pipeline, maintaining the reaction medium in a homogeneous liquid state. To monitor reaction conversion and reactor status, accurate determination of the content of each component in such media is necessary, with gas chromatography (GC) being the most common method for quantitative analysis. However, since laboratory analytical instruments and sample preparation methods are usually operated at atmospheric pressure, quantitative analysis of such pressurized samples presents additional challenges for analysts: maintaining high pressure throughout sampling and handling of such media is crucial; loss of pressure leads to phase separation, causing the gaseous sample to evaporate and escape, resulting in sample distortion.

[0003] In laboratory work, pressure vessels (such as gas cylinders) are generally used to sample materials under pressure. Then, methods are devised to quantitatively and accurately introduce the sample into the vaporization chamber of a gas chromatograph for quantitative analysis. For example, Chinese patent CN210923599 U discloses a high-pressure liquid sampler. During use, the vaporization of the liquid sample is judged by observing the viewing window. After observing that no bubbles are present in the sample, the liquid injection valve flow path is switched, and the liquid sample is directly and accurately introduced into the chromatographic injection port using a carrier gas. After vaporization and separation, the sample enters the chromatographic column for separation and then enters the detector for detection.

[0004] Existing injectors and injection methods have the following problems: First, existing technology connects one end of the sample inlet pipe to a gas cylinder and the other end directly to the atmosphere, making it impossible to control the pressure at the outlet of the inlet pipe. The pipe is in a state of continuous pressure drop, and the consistency of the sample injection is achieved by maintaining a basically constant outlet flow rate. In an ideal situation, this open-end pipe will also cause low-boiling-point substances to accumulate in the low-pressure area and escape from the open end, resulting in distorted analytical results. In actual operation, the actual pressure of the sample in the metering chamber depends on the distribution of the pressure drop throughout the inlet pipe. Even if the valve opening is exactly the same each time, it will be affected by multiple parameters such as the bending of the inlet pipe, temperature, sample viscosity, and the degree of filter contamination, exhibiting significant randomness, making it almost impossible to control the consistency of the sample injection.

[0005] Secondly, injection pressure loss occurs both during and after injection. After this pressure loss, a large amount of high-boiling-point substances in the sample cannot be carried away by the low-boiling-point components and will adhere to the inner surfaces of all components in the flow path, such as the tubing, valve chamber walls, and injection needle, in the form of droplets / liquid films. It is almost impossible to remove these substances by purging the injection line with room-temperature nitrogen. This random loss not only distorts the results of the current injection but also leads to contamination of the sample with residual high-boiling-point substances from the previous analysis in subsequent analyses, also causing random distortion. The residual tiny droplets, propelled by the gas flow, roll and fall into the vaporization chamber of the GC system after a random period of time, resulting in ghost peaks. Utility Model Content

[0006] To address the aforementioned problems, this invention provides a high-pressure injection device for gas chromatography analysis.

[0007] The technical solution adopted in this utility model is: A high-pressure injection device for gas chromatography analysis includes an injection line, a sampling device, a purge line, and a cleaning line; the injection line includes a switching valve, a line before the injection valve, a quantitative injection valve, and a line after the injection valve connected in sequence; the quantitative injection valve is provided with an injection chamber, a first gas chamber, a solvent chamber, and a second gas chamber. The switching sampling device, purge line and cleaning line are connected to the quantitative injection valve through the switching valve and the pipeline before the injection valve, respectively. The cleaning tubing is used to pump the cleaning solvent into the injection chamber sequentially through the solvent chamber, the switching valve, and the injection valve before the injection valve before the injection, to remove residual high-boiling-point substances and simultaneously quantitatively fill the solvent chamber. The purging line is used to purge the inlet line and injection chamber of the injection valve with inert gas after solvent cleaning, to remove residual cleaning solvent and other impurities. The sampling device is used to collect the sample to be tested and to replace the pipeline before the injection valve with the flowing pressurized sample, quantitatively filling the injection chamber after purging. The quantitative injection valve is used to allow the cleaning solvent filled in the solvent chamber and the injection chamber to enter the vaporization chamber under gas pressure along the injection needle, and to allow the solvent filled in the solvent chamber and the sample in the injection chamber to enter the chromatographic column under gas pressure for gas chromatography analysis.

[0008] Furthermore, the valve core of the quantitative injection valve is provided with a first chamber, a second chamber, a third chamber, a fourth chamber, and a fifth chamber arranged at 90° intervals in a clockwise direction. The first chamber serves as the injection chamber, the third chamber serves as the solvent chamber, and the second and fourth chambers serve as the first and second gas chambers, respectively. The valve body of the quantitative injection valve is provided with a first inlet and a first outlet, a second inlet and a second outlet, a third inlet and a third outlet, and a fourth inlet and a fourth outlet, respectively, corresponding to the first, second, third, and fourth chambers. The first inlet is connected to the outlet of the switching valve through the pre-vacuum injection line, and the first outlet is connected to the post-vacuum injection line. The second inlet is connected to the fourth outlet through a pipe, and the second outlet is connected to the sampling needle. The third inlet and the third outlet are connected to the cleaning line. The fourth inlet is connected to the carrier gas source of the GC system.

[0009] Furthermore, the sampling device includes a cylinder front valve, a cylinder front pressure gauge, a sample cylinder, and a cylinder rear valve connected in sequence.

[0010] Furthermore, the valve pre-injection line includes a first injection tube and an online filter installed on the first injection tube.

[0011] Furthermore, the post-valve injection pipeline includes a second injection tube and an observation tube, an outlet pressure gauge, an outlet pressure reducing valve, and a gas washing tank arranged sequentially on the second injection tube. The gas washing tank contains a liquid solvent that is miscible with the main components of the sample.

[0012] Furthermore, the purging pipeline includes a purging pipe and a purging valve installed on the purging pipe.

[0013] Furthermore, the cleaning pipeline includes cleaning pipes and a solvent pump installed on the cleaning pipes.

[0014] The beneficial effects of this utility model are: 1) By maintaining constant pressure throughout the entire injection pipeline and installing pressure gauges in front of the cylinder and pipeline pressure reducing valve, pressure monitoring and control within the pipeline can be achieved. This ensures that the material state within the pipeline is completely consistent each time a sample is injected, preventing the selective escape of low-boiling-point substances due to pressure drop within the pipeline, and guaranteeing the consistency and authenticity of the injection volume.

[0015] 2) Components with boiling points significantly higher than room temperature will remain in the injection line as oil droplets / films after sample phase separation, which cannot be removed by purging. This device incorporates a cleaning channel, using a pump to inject cleaning solvent into the injection line, which can wash away high-boiling-point substances that are difficult to remove by purging into the injection line and injection valve chamber, avoiding random interference with subsequent injections. The cleaning process also includes a pure solvent injection to remove high-boiling-point substances inside the injection needle.

[0016] 3) The above improvements ensure that the sample in the metering device is not distorted; however, regardless of the metering device structure used, the metered sample will inevitably lose pressure and undergo phase separation after the injection begins. High-boiling-point components adhere to the surface of the metering chamber and the injection needle and cannot be carried into the device by the carrier gas. This device innovatively introduces a quantitative solvent that flows through the quantitative injection valve along with the sample after the sample is injected, thereby washing the high-boiling-point components adhering in the flow path into the vaporization chamber, completely solving the problem of injection distortion. Furthermore, through the design of the pipeline and valve structure, sample injection and the subsequent solvent injection can be achieved with the same valve action, eliminating the need for complex valve systems and cumbersome program control devices.

[0017] 4) In view of the characteristic that the sample will become a gas-liquid mixture after being discharged from the pipeline, a gas washing tank and an exhaust pipe are added to separate the gas and liquid of the discharged sample and discharge them separately to avoid laboratory contamination problems. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the high-pressure injection device in this application.

[0019] Figure 2 This is a diagram showing the positions of each chamber in the initial state of the quantitative injection valve.

[0020] Figure 3 This is a diagram showing the positions of each chamber after the quantitative injection valve is rotated 90° clockwise. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below in conjunction with the accompanying drawings and preferred embodiments. Example

[0022] See Figure 1 A high-pressure injection device for gas chromatography analysis includes an injection line, a sampling device 30, a purge line 60, and a cleaning line 70; the injection line includes a switching valve 10, an injection valve pre-line 40, a quantitative injection valve 20, and an injection valve post-line 50 connected in sequence.

[0023] In this embodiment, the switching valve 10 is a three-position one-way valve, which is provided with a first switching valve inlet, a second switching valve inlet, a third switching valve inlet and a switching valve outlet.

[0024] The quantitative injection valve 20 is a dedicated valve for gas chromatography injection. In this embodiment, a pneumatic ten-channel quantitative injection valve is selected, and the volume of the metering valve chamber can be 0.5µL or 1µL. In other embodiments, two pneumatic pressure-resistant four-way liquid valves can be used in combination to replace valve chamber 1 / 2 and valve chamber 3 / 4 respectively, which can also achieve the same function.

[0025] In this embodiment, the valve disc of the quantitative injection valve 20 is provided with a first cavity 1, a second cavity 2, a third cavity 3, a fourth cavity 4, and a fifth cavity 5 arranged at 90° intervals in a clockwise direction. The first cavity 1 serves as the injection chamber, the third cavity 3 serves as the solvent chamber, and the second and fourth cavities serve as the first and second gas chambers, respectively. The valve body is provided with inlets and outlets that are respectively connected to each cavity; that is, the first inlet 1A and the first outlet 1B of the cavity, the second inlet 2A and the second outlet 2B of the cavity, and the third inlet 1A and the fifth outlet 1B of the cavity. 3A and the third outlet 3B of the cavity, as well as the fourth inlet 4A and the fourth outlet 4B of the cavity; the first inlet 1A of the cavity is connected to the outlet of the switching valve through the valve pre-sample line 40, and the first outlet 1B of the cavity is connected to the post-valve sample line 50; the second inlet 2A of the cavity is connected to the fourth outlet 4B of the cavity through a pipe, and the second outlet 2B of the cavity is connected to the sampling needle through a pipe; the third inlet 3A and the third outlet 3B of the cavity are connected to the cleaning line 70; the fourth inlet 4A of the cavity is connected to the carrier gas source of the GC system through a pipe.

[0026] See Figure 2 In the initial state, the injection chamber is connected to the first inlet 1A and the first outlet 1B of the chamber, the second chamber 2 is connected to the second inlet 2A and the second outlet 2B of the chamber, the solvent chamber is connected to the third inlet 3A and the third outlet 3B of the chamber, and the fourth chamber 4 is connected to the fourth inlet 4A and the fourth outlet 4B of the chamber.

[0027] See Figure 3 After rotating the quantitative injection valve 20 clockwise by 90°, the first chamber 1 rotates to the position of the second chamber 2, and the injection chamber is connected to the second inlet 2A and the second outlet 2B of the chamber. The second chamber 2 rotates to the position of the third chamber 3, and the second chamber 2 is connected to the third inlet 3A and the third outlet 3B of the chamber. The third chamber 3 rotates to the position of the fourth chamber 4, and the solvent chamber is connected to the fourth inlet 4A and the fourth outlet 4B of the chamber. The fourth chamber 4 rotates to the position of the fifth chamber 5.

[0028] The sampling device 30 includes a cylinder front valve 33, a cylinder front pressure gauge 32, a sample cylinder 33, and a cylinder rear valve 34 connected in sequence. During sample injection, the sampling device 30 is connected to the second inlet of the switching valve through its cylinder rear valve 34 and to the back pressure gas path through its cylinder front valve 33. The back pressure gas path uses the same gas pipeline as the GC carrier gas, and its pressure is not less than the pressure at the sample sampling point to prevent backflow.

[0029] The valve-inlet sample line 40 includes a first sample inlet tube and an online filter 41 installed on the sample inlet tube. The online filter 41 is used to filter impurities in the sample. The first sample inlet tube is connected to the outlet of the switching valve at its starting end and to the first inlet 1A of the cavity at its ending end.

[0030] The post-valve sample inlet line 50 consists of a second sample inlet tube, an observation tube 51, an outlet pressure gauge 52, an outlet pressure reducing valve 53, and a gas washing tank 54. The observation tube 51, the outlet pressure gauge 52, the outlet pressure reducing valve 53, and the gas washing tank 54 are connected sequentially through the second sample inlet tube. The starting end of the second sample inlet tube is connected to the first outlet 1B of the cavity, and the end is inserted into the gas washing tank 54. The outlet pressure reducing valve 53 can be a liquid pressure reducing valve or a back pressure valve. The gas washing tank 54 is equipped with an exhaust pipe 55 and contains a liquid solvent miscible with the main components of the sample to achieve waste gas / waste liquid separation.

[0031] The purge line 60 includes a purge pipe and a purge valve 61 installed on the purge pipe. The starting end of the purge pipe is used to connect to the purge gas source, and the ending end of the purge pipe is connected to the first inlet of the switching valve. The purge gas source can be a GC carrier gas source.

[0032] The cleaning pipeline 70 includes a first cleaning pipeline, a solvent pump 71 mounted on the first cleaning pipeline, and a second cleaning pipeline. The first cleaning pipeline starts at a solvent tank and ends at a third inlet 3A of the cavity. The second cleaning pipeline starts at a third outlet 3B of the cavity and ends at a third inlet of a switching valve. The solvent pump 71 can be a peristaltic pump, a dual-plunger pump, or a diaphragm pump, with a flow rate of 3~10 mL / min.

[0033] The operating method of the above-mentioned high-pressure injection device is as follows: 1. Sample preparation: After sampling, the sampling device 30 is connected to the sampling point and sent to the analysis chamber. One end of the sampling device 30 is connected to the back pressure gas circuit through the front valve 33 of the gas cylinder, and the other end is connected to the third inlet of the switching valve through the rear valve 34 of the gas cylinder. The switching valve 10 is switched to the flushing channel, so that the third inlet of the switching valve is connected to the outlet of the switching valve. 2. Cleaning and purging: 2.1) Solvent pump 71 is turned on, and solvent is pumped into the third chamber 3 (solvent chamber) through the first cleaning pipeline, and then flows into the first chamber 1 sequentially through the second cleaning pipeline, switching valve 10, and valve inlet sample line 40; after the first chamber 1 is filled with solvent, the GC system supplies gas to the quantitative injection valve 20, and the quantitative injection valve 20 is rotated 90° clockwise (e.g., ...). Figure 3 As shown), the solvents in the first chamber 1 and the third chamber 3 are successively blown into the vaporization chamber along the injection needle 81 under the carrier gas pressure of the GC system, cleaning the contact surfaces of the injection needle and the valve core; then the gas supply is turned off, and the quantitative injection valve 20 returns to its initial position (as shown). Figure 2 As shown), solvent pump 71 fills the solvent chamber and injection chamber with solvent again in a quantitative manner. After filling is completed, solvent pump 71 is turned off and switching valve 10 is switched to the purge channel. 2.2) Open the purge valve 61. The inert gas flows sequentially through the switching valve 10, the inlet sample line, the first chamber 1 and the outlet sample line. After 10 minutes, the switching valve 10 switches to the sample inlet channel.

[0034] This step uses solvent to clean the injection tubing, the quantitative injection valve chamber, and the injection needle to remove any high-boiling-point materials that may be present. Then, carrier gas is used to purge the solvent from the injection tubing and the quantitative injection valve chamber. At the end of step 2.1, the first chamber 1 and the third chamber 3 are filled with clean solvent; at the end of step 2.2, the third chamber 3 of the quantitative injection valve remains filled with solvent, while the other valve chambers contain carrier gas.

[0035] 3. Preparation before sample injection: First, close the outlet pressure reducing valve 53 and switch the switching valve 10 to the sample injection channel; then open the cylinder inlet valve 31 and cylinder outlet valve 34, so that the sample in cylinder 33 flows into the first chamber 1 through the switching valve 10 and the online filter 41 in sequence. Next, open the outlet pressure reducing valve 53 appropriately, so that the sample flows through the observation tube 51, the outlet pressure gauge 52, and the outlet pressure reducing valve 53 in sequence, and enters the gas washing tank 54; adjust the opening of the outlet pressure reducing valve 53 to ensure that the readings of the cylinder pressure gauge 32 and the outlet pressure gauge 52 are consistent, and that there are no air bubbles in the observation tube 51. After the sample has fully rinsed the sample injection pipeline, close the outlet pressure reducing valve 53.

[0036] This step uses a flowing, pressurized sample to fully displace the carrier gas in the injection line, ensuring adsorption equilibrium is reached on the tube wall and avoiding phase separation distortion caused by pressure drop. At the end of the step, the injection chamber is filled with sample at constant pressure, the solvent chamber is filled with solvent, and the other chambers contain carrier gas.

[0037] 4. Sample injection: The GC system supplies gas to the quantitative injection valve 20, and rotates the quantitative injection valve 90° clockwise (see...). Figure 3 The sample in chamber 1 and the solvent in chamber 3 are sequentially introduced into the chromatographic column through injection needle 81 under the carrier gas pressure of the GC system for gas chromatography analysis. After 30 seconds, the gas supply is turned off, the quantitative injection valve 20 is rotated back to its initial position, the cylinder inlet valve 31 and cylinder outlet valve 34 are closed, and the switching valve 10 is switched to the flushing channel, completing the injection process.

[0038] During this step of sample injection, the sample in the first chamber 1 is first depressurized and blown into the vaporization chamber (at this time, phase separation and high-boiling-point substance droplets / liquid film residues may occur). Then, the solvent in the third chamber 3 is introduced into the vaporization chamber through the first chamber 1 and the injection needle 81 to clean the injection chamber and injection needle and remove the residual high-boiling-point substances.

[0039] The above description is only a preferred embodiment of the present utility model. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present utility model, and these improvements and modifications are also within the protection scope of the present utility model.

Claims

1. A high-pressure injection device for gas chromatography analysis, characterized in that, It includes an injection line, a sampling device (30), a purge line (60), and a cleaning line (70); the injection line includes a switching valve (10), an injection valve pre-line (40), a quantitative injection valve (20), and an injection valve post-line (50) connected in sequence; the quantitative injection valve (20) is provided with an injection chamber, a first gas chamber, a solvent chamber, and a second gas chamber; The switching sampling device (30), the purging line (60) and the cleaning line (70) are connected to the quantitative injection valve (20) through the switching valve and the inlet line (40) of the injection valve, respectively. The cleaning line (70) is used to pump the cleaning solvent into the injection chamber in sequence through the solvent chamber, the switching valve, and the injection valve before the injection valve before the injection, to remove residual high-boiling-point substances and at the same time quantitatively fill the solvent chamber. The purging line (60) is used to purge the pre-injection line and injection chamber of the injection valve with inert gas after solvent cleaning, to remove residual cleaning solvent and impurities; The sampling device (30) is used to collect the sample to be tested and to replace the pipeline before the injection valve with the flowing pressurized sample to quantitatively fill the injection chamber after purging. The quantitative injection valve (20) is used to allow the cleaning solvent filled in the solvent chamber and the injection chamber to enter the vaporization chamber under gas pressure along the injection needle, and to allow the solvent filled in the solvent chamber and the sample in the injection chamber to enter the chromatographic column under gas pressure for gas chromatography analysis.

2. The high-pressure injection device for gas chromatography analysis according to claim 1, characterized in that, The valve core of the quantitative injection valve (20) is provided with a first chamber (1), a second chamber (2), a third chamber (3), a fourth chamber (4), and a fifth chamber (5) arranged at 90° intervals in a clockwise direction. The first chamber (1) serves as the injection chamber, the third chamber (3) serves as the solvent chamber, and the second chamber (2) and the fourth chamber (4) serve as the first gas chamber and the second gas chamber, respectively. The valve body of the quantitative injection valve (20) is provided with a first inlet (1A) and a first outlet (1B) of the cavity corresponding to the first chamber (1), the second chamber (2), the third chamber (3), and the fourth chamber (4), respectively. The chamber has two outlets (2B), a third inlet (3A) and a third outlet (3B), a fourth inlet (4A) and a fourth outlet (4B); the first inlet (1A) is connected to the outlet of the switching valve via the pre-valve sampling line (40), and the first outlet (1B) is connected to the post-valve sampling line (50); the second inlet (2A) is connected to the fourth outlet (4B) via a pipe, and the second outlet (2B) is connected to the sampling needle (81); the third inlet (3A) and the third outlet (3B) are connected to the cleaning line (70); and the fourth inlet (4A) is connected to the carrier gas source of the GC system.

3. The high-pressure injection device for gas chromatography analysis according to claim 1, characterized in that, The sampling device (30) includes a cylinder front valve (31), a cylinder front pressure gauge (32), a sample cylinder (33), and a cylinder rear valve (34) connected in sequence.

4. A high-pressure injection device for gas chromatography analysis according to claim 1, characterized in that, The inlet line (40) includes a first inlet tube and an online filter (41) installed on the first inlet tube.

5. A high-pressure injection device for gas chromatography analysis according to claim 1, characterized in that, The pipeline (50) after the injection valve includes a second injection tube and an observation tube (51), an outlet pressure gauge (52), an outlet pressure reducing valve (53), and a gas washing tank (54) arranged sequentially on the second injection tube. The gas washing tank (54) contains a liquid solvent that is miscible with the main components of the sample.

6. A high-pressure injection device for gas chromatography analysis according to claim 1, characterized in that, The purge line (60) includes a purge pipe and a purge valve (61) installed on the purge pipe.

7. A high-pressure injection device for gas chromatography analysis according to claim 1, characterized in that, The cleaning pipeline (70) includes a cleaning pipe and a solvent pump (71) installed on the cleaning pipe.

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