A device and method for automatically preparing a gas standard curve

Abstract

The present invention discloses a device and method for automatically preparing a gas standard curve, which belongs to the field of instrumental analysis technology, and includes a standard gas preparation and injection unit and a chromatographic unit; the standard gas preparation and injection unit includes a standard gas container, a selection valve, an injection valve, a solenoid valve, an air block and a vacuum pump connected in sequence, the solenoid valve is also connected to an inert gas input pipeline, and the air block is connected to the air inlet of the vacuum pump; the chromatographic unit includes a first chromatographic column, a second chromatographic column, a first carrier gas pipeline, a second carrier gas pipeline and a detector. The present invention reduces the burden on detection personnel, improves work efficiency, avoids errors when manually preparing a standard curve, automatically prepares multiple concentration points, and avoids mixing of air into a syringe during multiple extractions, thereby interfering with the analysis results.

Description

Technical Field

[0001] The invention relates to the technical field of instrument analysis, and in particular to a device and method for automatically preparing a gas standard curve. Background Art

[0002] The standard curve method (i.e., external standard method) is a method widely used in gas chromatography analysis. In the initial stage, both liquid and gas were prepared manually. Since manual preparation is prone to human errors, it requires high standards for experimental personnel. In recent years, with the hot sales of liquid quantitative sampling and sample separation devices such as pipettes and dispensers, the difficulty of preparing liquid standard sample concentrations has been greatly reduced, and the requirements for personnel have gradually decreased. However, in terms of the preparation of gas standard sample concentrations, the existing gas dilution devices cannot perform frequent preparation of small volumes and multiple varieties on site, and users have continued to use manual preparation methods.

[0003] There are two existing methods for preparing standard gas concentrations. One is that the standard sample manufacturer prepares a large volume and then packs it into cylinders and sells it to users. The other is on-site manual preparation. The manual preparation method is to use a 100ml glass syringe to extract a certain amount of standard sample, and then manually add a certain amount of nitrogen or other inert gas to dilute it, and then inject it into the gas chromatograph for analysis. Since the standard curve needs to take multiple concentration points, each concentration point must be manually taken from the syringe, the standard gas must be extracted, and then mixed with nitrogen, so the operator needs to repeat this step many times to complete the drawing of the standard curve. Not only is it time-consuming and laborious, but when the standard sample is transferred through the syringe, due to the sealing problem of the glass syringe and the syringe being easily mixed with air more or less during multiple extractions, the analysis results are interfered with, resulting in deviations in the standard curve. The existing gas dilution device can only prepare large volumes of single-point concentration standard gas, which is then distributed to users after being packed into cylinders. Users need to take standard gas from cylinders of each concentration for analysis, and the standard gas sample is easily contaminated during gas transfer. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] The present invention provides a device and method for automatically preparing a gas standard curve, which solves the problems of human error and repeatability error generated by manual preparation of standard gas and pollution of standard gas during the preparation process.

[0006] (II) Technical solution

[0007] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0008] A device for automatically preparing a gas standard curve, comprising a standard gas preparation and injection unit and a chromatography unit;

[0009] The standard gas preparation and injection unit comprises a standard gas container, a selection valve, an injection valve, a solenoid valve, an air block and a vacuum pump which are connected in sequence, the solenoid valve is also connected to an inert gas input pipeline, the air block is connected to the air inlet of the vacuum pump, the air outlet of the vacuum pump and the selection valve are both connected to a discharge port, and the injection valve is provided with a quantitative ring;

[0010] The chromatographic unit includes a first chromatographic column, a second chromatographic column, a first carrier gas pipeline, a second carrier gas pipeline and a detector. The first carrier gas pipeline, the injection valve and the first chromatographic column are connected in sequence, the second carrier gas pipeline, the injection valve and the second chromatographic column are connected in sequence, and the first chromatographic column and the second chromatographic column are connected to the detector respectively.

[0011] Preferably, the solenoid valve is a 2-position 3-way solenoid valve.

[0012] Preferably, the standard gas container is a variable-volume gas bag or a syringe.

[0013] Preferably, the injection valve is a pneumatic or electric 2-position multi-way valve, and the selection valve is a pneumatic or electric multi-position multi-way valve.

[0014] Among them, preferably, the injection valve is a 2-position 6-way injection valve or a 2-position 10-way injection valve, and the selection valve is an 8-position 8-way selection valve, a 12-position 12-way selection valve or a 16-position 16-way selection valve.

[0015] Among them, preferably, a pressure stabilizing valve and a flow stabilizing valve are sequentially provided on the inert gas input pipeline according to the conveying direction.

[0016] Wherein, preferably, the gas resistance is a fixed gas resistance, an adjustable gas resistance or a mass flow controller.

[0017] A method for automatically preparing a gas standard curve is to calculate through a program the amount of standard gas to be extracted and emptied and the amount of inert gas to be input when preparing the concentration of each point, so as to achieve point-by-point dilution of the standard gas, thereby obtaining samples of various concentrations; when extracting, a vacuum pump and a gas resistor are used in combination to achieve a stable extraction flow rate; when inputting the inert gas, a voltage-stabilizing and flow-stabilizing valve is used to ensure the stability of the flow rate of the input inert gas; an electromagnetic valve is used to control the switching of the extraction and input flow paths; a switching valve and a selection valve are used in combination to achieve the purge of the residual sample inside the pipeline by the inert gas, so as to ensure that high and low concentrations do not interfere with each other;

[0018] Workflow: Use a container to take a certain amount of fixed-concentration standard gas, connect it to any interface of the selection valve, set the current concentration and volume of the standard gas and the maximum volume of the container, and set the concentration point of the standard sample. After the setting is completed, the device automatically runs the process: evacuation-purge-input-sampling-balance-injection, and analyzes the first concentration point; the process runs once for each concentration point until the last concentration point is analyzed.

[0019] The automatic operation process of the device includes the following steps:

[0020] (1) Emptying: Switch the selection valve to communicate with the container, switch the injection valve to the sampling state connected to the quantitative loop, switch the solenoid valve to communicate with the vacuum pump flow path, and the vacuum pump extracts according to the program calculation to achieve the purpose of extracting quantitative gas samples;

[0021] (2) Purge: The selector valve is switched to the flow path connected to the exhaust port, the injection valve is switched to the sampling state connected to the quantitative loop, the solenoid valve is switched to the inert gas flow path, and the inert gas passes through the entire input pipeline and is discharged from the exhaust port;

[0022] (3) Input: The selector valve is switched to a flow path connected to the container, the injection valve is switched to a sampling state connected to the quantitative loop, the solenoid valve is switched to a flow path connected to the inert gas, and the inert gas is introduced into the container after passing through the entire input pipeline. The amount of gas introduced is controlled by time;

[0023] (4) Sampling: Fill the quantitative loop with the sample of the prepared concentration to prepare for injection. The selector valve is switched to connect with the container, the injection valve is switched to the sampling state connected with the quantitative loop, the solenoid valve is switched to connect with the vacuum pump flow path, and the vacuum pump stops after working for a corresponding time according to the value calculated by the program, so that the sample volume fills the quantitative loop;

[0024] (5) Balance: Close the pipeline so that the quantitative loop is connected only to the container to achieve pressure balance. The injection valve is switched to the sampling state connected to the quantitative loop. The solenoid valve is switched to the flow path connected to the vacuum pump, and the vacuum pump is turned off.

[0025] (6) Injection: Switch the injection valve to connect the carrier gas to the quantitative loop, and push the standard gas with a prepared concentration and stable pressure into the gas chromatograph for analysis.

[0026] (III) Beneficial effects

[0027] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0028] The purpose of the present invention is to reduce the burden on test personnel, improve work efficiency and avoid errors in manually preparing standard curves. The prepared standard samples can be automatically injected into the gas chromatograph for analysis; multiple concentration points are automatically prepared to avoid mixing air into the syringe during multiple extractions, which interferes with the analysis results. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other embodiments can be obtained based on these drawings without creative work.

[0030] Figure 1 It is a process flow chart of the emptying process in the present invention;

[0031] Figure 2 It is a process flow chart of the purging process in the present invention;

[0032] Figure 3 A process flow chart for the input process of the present invention;

[0033] Figure 4 It is a process flow chart of the sampling process in the present invention;

[0034] Figure 5 is a process flow chart of the balancing step in the present invention;

[0035] Figure 6 It is a process flow chart of the sample injection process in the present invention;

[0036] Figure 7 is a standard curve diagram of total hydrocarbons in the present invention;

[0037] Figure 8 is a standard curve diagram of methane in the present invention;

[0038] Fig. 9 It is a gas chromatogram of an embodiment of the present invention.

[0039] In the figure: 1. Standard gas container, 2. Selection valve, 3. Injection valve, 4. Solenoid valve, 5. Gas resistance, 6. Vacuum pump, 7. Discharge port, 8. First chromatographic column, 9. Second chromatographic column, 10. First carrier gas pipeline, 11. Second carrier gas pipeline, 12. Detector, 13. Pressure regulating valve, 14. Flow regulating valve, 15. Vacuum pump inlet, 16. Vacuum pump outlet DETAILED DESCRIPTION

[0040] The technical solution of the present invention will be clearly and completely described below in conjunction with the specific embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] This embodiment provides a device for automatically preparing a gas standard curve, including a standard gas preparation and injection unit and a chromatography unit;

[0042] The standard gas preparation and injection unit comprises a standard gas container 1, a selection valve 2, an injection valve 3, a solenoid valve 4, an air block 5 and a vacuum pump 6 which are connected in sequence. The solenoid valve 4 is also connected to an inert gas input pipeline. The air block 5 is connected to an air inlet 15 of the vacuum pump. The air outlet of the vacuum pump 6 and the selection valve 2 are both connected to an exhaust port 7. Figure 1 As shown, the vacuum pump 6 and the selection valve 2 share a discharge port 7, or they may not share a discharge port and each of them has a discharge port. The injection valve 3 is provided with a quantitative ring;

[0043] The chromatographic unit includes a first chromatographic column 8, a second chromatographic column 9, a first carrier gas pipeline 10, a second carrier gas pipeline 11 and a detector 12. The first carrier gas pipeline 10, the injection valve 3 and the first chromatographic column 8 are connected in sequence, the second carrier gas pipeline 11, the injection valve 3 and the second chromatographic column 9 are connected in sequence, and the first chromatographic column 8 and the second chromatographic column 9 are respectively connected to the detector 12.

[0044] The solenoid valve 4 is a 2-position 3-way solenoid valve 4 .

[0045] The standard gas container 1 in the present invention is a gas bag or a syringe with a variable volume.

[0046] The injection valve 3 is an electric 2-position 10-way injection valve 3 , and in the present invention, it can also be a pneumatic 2-position 10-way injection valve 3 or a pneumatic or electric 2-position 6-way injection valve 3 or a 2-position multi-way injection valve 3 .

[0047] Among them, the selection valve 2 is an electric 12-position 12-way selection valve 2, and in the present invention it can also be a pneumatic or electric 12-position 12-way selection valve 2, an 8-position 8-way selection valve 2 or a 16-position 16-way selection valve 2 or a multi-position multi-way selection valve 2.

[0048] The inert gas input pipeline is provided with a pressure stabilizing valve 13 and a flow stabilizing valve 14 in sequence according to the conveying direction to ensure the flow rate of the input inert gas is stable.

[0049] The gas resistance 5 is a fixed gas resistance 5 or an adjustable gas resistance 5 or a mass flow controller 5 .

[0050] This embodiment also provides a method for automatically preparing a gas standard curve, the working principle of which is to calculate the amount of standard gas to be extracted and emptied and the amount of inert gas to be input when preparing the concentration of each point through a program, so as to achieve point-by-point dilution of the standard gas, thereby obtaining samples of various concentrations. When extracting, a vacuum pump 6 and a gas resistor 5 are used to achieve a stable extraction flow rate. When inputting inert gas, a pressure regulating valve 13 and a flow regulating valve 14 are used to ensure the stability of the flow rate of the input inert gas, and an electromagnetic valve 4 is used to control the switching of the extraction and input flow paths; the injection valve 3 and the selection valve 2 are used to switch to realize the purge of the residual sample inside the pipeline with inert gas, so as to ensure that high and low concentrations do not interfere with each other;

[0051] Workflow: Use a container to take a certain amount of fixed-concentration standard gas, connect it to any interface of selection valve 2, set the current concentration and volume of the standard gas and the maximum volume of the container, and set the concentration point of the standard sample. After the setting is completed, the device automatically runs the process: evacuation-purge-input-sampling-balance-injection, and analyzes the first concentration point; the process runs once for each concentration point until the last concentration point is analyzed.

[0052] The automatic operation process of the device includes the following steps:

[0053] (1) Exhaust: To ensure that the inert gas does not reach the maximum volume of the container after input, some of the standard gas needs to be exhausted first. Switch the selector valve 2 to connect with the container, switch the injection valve 3 to the sampling state connected with the quantitative loop, switch the solenoid valve 4 to connect with the flow path of the vacuum pump 6, and the vacuum pump 6 extracts according to the program calculation to achieve the purpose of extracting quantitative gas samples (see the process flow chart). Figure 1 , where the solid arrow indicates the process flow chart of the emptying process);

[0054] (2) Purging: To prevent the residual sample in the pipeline from being pushed back into the container by the inert gas during evacuation, purging is required to blow out the residual sample in the pipeline. Selector valve 2 is switched to the flow path connected to the discharge port, injection valve 3 is switched to the sampling state connected to the quantitative loop, solenoid valve 4 is switched to the inert gas flow path, and the inert gas passes through the entire input pipeline and is discharged from the discharge port (see the process flow chart). Figure 2 , where the solid arrow indicates the process flow chart of the purge process);

[0055] (3) Input: Selector valve 2 switches to the flow path connected to the container, injection valve 3 switches to the sampling state connected to the quantitative loop, solenoid valve 4 switches to the inert gas flow path, and the inert gas passes through the entire input pipeline into the container. The amount of gas introduced is controlled by time (see the process flow chart). Figure 3 , where the solid arrow indicates the process flow diagram of the input process);

[0056] (4) Sampling: Fill the quantitative loop with the sample of the prepared concentration to prepare for injection. Selector valve 2 is switched to connect with the container, injection valve 3 is switched to the sampling state connected with the quantitative loop, solenoid valve 4 is switched to connect with the flow path of vacuum pump 6, and vacuum pump 6 stops after working for a corresponding time according to the value calculated by the program, so that the sample volume fills the quantitative loop (see the process flow chart). Figure 4 , where the solid arrow indicates the process flow chart of the sampling process);

[0057] (5) Balance: Close the pipeline so that the quantitative loop is connected only to the container to achieve pressure balance. The injection valve 3 is switched to the sampling state connected to the quantitative loop. The solenoid valve 4 is switched to the flow path connected to the vacuum pump 6. The vacuum pump 6 is turned off (see the process flow chart). Figure 5 , where the solid arrow indicates the process flow diagram of the balancing process);

[0058] (6) Injection: Switch injection valve 3 to connect the carrier gas to the quantitative loop, and push the standard gas with a prepared concentration and stable pressure into the gas chromatograph for analysis (see the process flow chart). Figure 6 , where the solid arrow indicates the process flow diagram of the injection step).

[0059] At this point, the preparation of the first concentration point has been completed. Then, according to the value of the first concentration point and the remaining sample volume in the container after injection, the concentration preparation of the next point continues until the preparation of all concentration points is completed.

[0060] The automatic concentration configuration data of methane standard gas in this embodiment is shown in the following table:

[0061] Concentration (ppm) 0 1 2 4 8 16 Total hydrocarbon area 0 1403 3013 5977 11796 23151

[0062] Concentration (ppm) 0 1 2 4 8 16 Methane area 0 1489 3039 6126 12077 23579

[0063] Among them, the standard curve of total hydrocarbons is as follows Figure 7 The standard curve of methane is shown in Figure 8 The corresponding gas chromatogram is shown in Fig. 9 shown.

[0064] It should be noted that, in this article, terms such as "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of more restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0065] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for automatically preparing a gas standard curve, characterized in that: The program calculates the amount of standard gas to be extracted and emptied and the amount of inert gas to be input when preparing the concentration at each point, so as to achieve point-by-point dilution of the standard gas, thereby obtaining samples of various concentrations. When extracting, a vacuum pump and a gas resistor are used to achieve a stable extraction flow rate. When inputting inert gas, a voltage-stabilizing and flow-stabilizing valve is used to ensure the stability of the input inert gas flow rate, and an electromagnetic valve is used to control the switching of the extraction and input flow paths; the selection valve, injection valve and electromagnetic valve are used to switch to achieve the purge of the residual sample inside the pipeline with inert gas, so as to ensure that high and low concentrations do not interfere with each other; Workflow: Use a container to take a certain amount of fixed-concentration standard gas, connect to any interface of the selection valve, set the current standard gas concentration and volume and the maximum volume of the container, set the concentration point of the standard sample, and after the setting is completed, the device automatically runs the process: evacuation-purge-input-sampling-balance-injection, analyze the first concentration point; run the process once for each concentration point until the last concentration point is analyzed; The device used for automatically preparing the gas standard curve includes a standard gas preparation and injection unit and a chromatography unit; The standard gas preparation and injection unit comprises a standard gas container, a selection valve, an injection valve, a solenoid valve, an air block and a vacuum pump which are connected in sequence, the solenoid valve is also connected to an inert gas input pipeline, the air block is connected to the air inlet of the vacuum pump, the air outlet of the vacuum pump and the selection valve are both connected to a discharge port, and the injection valve is provided with a quantitative ring; The chromatographic unit comprises a first chromatographic column, a second chromatographic column, a first carrier gas pipeline, a second carrier gas pipeline and a detector, wherein the first carrier gas pipeline, the injection valve and the first chromatographic column are connected in sequence, the second carrier gas pipeline, the injection valve and the second chromatographic column are connected in sequence, and the first chromatographic column and the second chromatographic column are connected to the detector respectively; The inert gas input pipeline is provided with a pressure stabilizing valve and a flow stabilizing valve in sequence according to the conveying direction; The automatic operation process of the device includes the following steps: (1) Emptying: Switch the selection valve to communicate with the container, switch the injection valve to the sampling state connected to the quantitative loop, switch the solenoid valve to communicate with the vacuum pump flow path, and the vacuum pump extracts according to the program calculation to achieve the purpose of extracting quantitative gas samples; (2) Purge: The selector valve is switched to the flow path connected to the exhaust port, the injection valve is switched to the sampling state connected to the quantitative loop, the solenoid valve is switched to the inert gas flow path, and the inert gas passes through the entire input pipeline and is discharged from the exhaust port; (3) Input: The selector valve is switched to a flow path connected to the container, the injection valve is switched to a sampling state connected to the quantitative loop, the solenoid valve is switched to a flow path connected to the inert gas, and the inert gas is introduced into the container after passing through the entire input pipeline. The amount of gas introduced is controlled by time; (4) Sampling: Fill the quantitative loop with the sample of the prepared concentration to prepare for injection. The selector valve is switched to connect with the container, the injection valve is switched to the sampling state connected with the quantitative loop, the solenoid valve is switched to connect with the vacuum pump flow path, and the vacuum pump stops after working for a corresponding time according to the value calculated by the program, so that the sample volume fills the quantitative loop; (5) Balance: Close the pipeline so that the quantitative loop is connected only to the container to achieve pressure balance. The injection valve is switched to the sampling state connected to the quantitative loop, the solenoid valve is switched to the flow path connected to the vacuum pump, and the vacuum pump is turned off. (6) Injection: Switch the injection valve to connect the carrier gas to the quantitative loop, and push the standard gas with a prepared concentration and stable pressure into the gas chromatograph for analysis.

2. The method for automatically preparing a gas calibration curve according to claim 1, characterized in that: The solenoid valve is a 2-position 3-way solenoid valve.

3. The method for automatically preparing a gas standard curve according to claim 1, characterized in that: The standard gas container is a gas bag or a syringe with variable volume.

4. The method for automatically preparing a gas standard curve according to claim 1, characterized in that: The injection valve is a pneumatic or electric 2-position multi-way valve, and the selection valve is a pneumatic or electric multi-position multi-way valve.

5. The method for automatically preparing a gas standard curve according to claim 4, characterized in that: The injection valve is a 2-position 6-way injection valve or a 2-position 10-way injection valve, and the selection valve is an 8-position 8-way selection valve, a 12-position 12-way selection valve or a 16-position 16-way selection valve.

6. The method for automatically preparing a gas standard curve according to claim 1, characterized in that: The gas resistance is a fixed gas resistance, an adjustable gas resistance or a mass flow controller.

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