Enrichment device for measuring trace benzene in common gas

Abstract

The utility model discloses an enrichment device for measuring trace benzene in common gas, which comprises a three-way valve I, a liquid injector, a solid-phase extraction column, a gas sample tank, a three-way valve II, a waste liquid bottle and a sample collection bottle, the three-way valve I is provided with three ports A, B and C. The liquid injector is connected with the port A above the three-way valve I, an inlet of the solid-phase extraction column is connected with the port B below the three-way valve I, and an outlet of the solid-phase extraction column is connected with the port C below the three-way valve II. The gas sample tank is connected with the port C, the three-way valve II is provided with a port D, a port E and a port F, the port D is connected with an outlet of the solid-phase extraction column located above the port D, the port E is connected with the waste liquid bottle, and the port F is connected with the sample collection bottle. Compared with a large instrument in the prior art, the device disclosed by the utility model is simple in structure, low in cost and easy to assemble and operate, does not need to be equipped with an expensive thermal desorption instrument and a special gas sample injector, and is better in accuracy and repeatability of a detection result.

Description

Technical Field

[0001] The utility model relates to the technical field of gas detection, and particularly relates to an enrichment device for determining trace benzene in common gases. Background Art

[0002] Common gases such as carbon dioxide, nitrogen, argon, etc. are widely used as raw material gases in medicine, chemical industry, food and regulators. The benzene content in the raw material gases for industrial production is relatively high, which may cause hazards such as respiratory discomfort, damage to the central nervous system, inhibition of bone marrow hematopoietic function, influence on fertility, and damage to liver health. Even more, it may even induce leukemia and malignant tumors. Therefore, in the process of producing food-grade or medicine-grade products with raw material gases, it is necessary to purify the benzene in the raw material gases to prevent harm to human health.

[0003] Currently, to enrich benzene in gases, usually an "adsorption tube" is used to adsorb benzene in the gas at room temperature, then a thermal desorption instrument is used to perform high-temperature desorption on the adsorbed benzene, and finally, through direct gas injection, detection is carried out using GC or GC-MS (for the process flow chart, see Figure 3 ). However, in practical applications, during the process of "room-temperature adsorption and high-temperature desorption", there is loss of gas when the gas encounters high temperature, which will also cause a certain deviation in the final result. In addition, when connecting the gas for detection to a gas chromatograph, a special gas sampler and a thermal desorption instrument need to be equipped specifically. The cost of instrument transformation is very high, and the GC-MS itself is expensive. The costs of the enterprise's upfront investment, instrument transformation, and later maintenance using this method are all very high.

[0004] Therefore, in order to solve the problems existing in the prior art, it is necessary to construct a pretreatment device for detecting trace benzene in common gases, which can directly perform detection using common gas chromatography (GC) liquid injection after processing the gas to be detected, so as to solve the drawbacks of low popularity rate of equipment for detecting extremely low content benzene in laboratories and high investment in instrument hardware. Summary of the Invention

[0005] The purpose of the utility model is to provide an enrichment device for determining trace benzene in common gases, which has a simple structure, a simple operation process, and high accuracy, aiming at the problems existing in the prior art.

[0006] The technical solution of the present utility model is as follows: An enrichment device for the determination of trace benzene in common gases, comprising a three-way valve I, a syringe, a solid-phase extraction column, a gas sample tank, a three-way valve II, a waste liquid bottle and a sample collection bottle. The three-way valve I is provided with three ports A, B, and C. The syringe is connected to the port A above the three-way valve I for injecting activation liquid and elution liquid. The inlet of the solid-phase extraction column is connected to the port B below the three-way valve I through a pipeline. The solid-phase extraction column is filled with an adsorption packing for adsorbing benzene. The gas sample tank is connected to the port C through a gas distribution pipe. The three-way valve II is provided with three ports D, E, and F. The port D is connected to the outlet of the solid-phase extraction column above it through a pipeline. The port E is connected to the waste liquid bottle through a pipeline. The port F is connected to the sample collection bottle through a pipeline.

[0007] Further, the adsorption packing is Tenax TA.

[0008] Further, a gas flow control valve is provided on the gas distribution pipe connecting the gas sample tank and the port C of the three-way valve I.

[0009] Further, the syringe is provided with a metering scale and is detachably connected to the port A of the three-way valve I.

[0010] Further, a catheter extending to the bottom of the bottle is provided in the waste liquid bottle. The end of the catheter is a beveled opening. Water that can submerge the beveled end of the catheter can be added to the waste liquid bottle to facilitate verifying whether the gas in the gas sample tank has been sampled. If it is carbon dioxide gas, sodium hydroxide solution can be added to absorb it.

[0011] Further, the gas in the gas sample tank includes but is not limited to carbon dioxide or inert gas, and the inert gas can be nitrogen, argon, etc.

[0012] Further, the activation liquid and the elution liquid are methanol and N-methylpyrrolidone respectively.

[0013] Compared with the prior art, the beneficial effects of the present utility model are as follows:

[0014] The solid-phase extraction column of the present utility model selects Tenax TA as the adsorption packing to extract benzene in the gas, combines a three-way valve to realize the switching of the gas-liquid passage, and uses the strong elution solvent N-methylpyrrolidone to elute and collect benzene, realizing the enrichment of trace benzene in the commonly used gas of gas adsorption - liquid desorption. Compared with the prior art that uses a Tenax-GR adsorption tube to adsorb carbon dioxide at low temperature, after the adsorption is completed, the adsorption tube is loaded into a thermal desorption instrument, and the thermal desorption instrument desorbs the benzene in the adsorption tube through high temperature. At the same time, the thermal desorption instrument is connected to a GC-MS, and then the trace benzene is detected through a gas chromatography - mass spectrometry system; the present utility model not only has a simple structure, low cost, is easy to assemble and operate, does not require expensive thermal desorption instruments and special gas samplers, but also has better accuracy and repeatability of the detection results. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a schematic structural diagram of the present utility model;

[0016] Figure 2 is a working flow chart of the present utility model;

[0017] Figure 3 is a process flow chart of the prior art.

[0018] Among them, 1 - three-way valve I, 2 - solid-phase extraction column, 3 - adsorption packing, 4 - three-way valve II, 5 - gas sample tank, 6 - waste liquid bottle, 7 - conduit, 8 - sample collection bottle, 9 - gas flow control valve, 10 - syringe. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0019] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present utility model. The instruments, materials or reagents used in the present utility model are all commercially available products.

[0020] Embodiment 1

[0021] As Figure 1 shown, an enrichment device for determining trace benzene in a commonly used gas includes a three-way valve (I) 1, a syringe 10, a solid-phase extraction column 2, a gas sample tank 5, a three-way valve (II) 4, a waste liquid bottle 6, and a sample collection bottle 8.

[0022] The three-way valve (I) 1 is provided with three ports A, B, and C. The syringe 10 is connected to the A port located above the three-way valve (I) 1. The syringe 10 is provided with a measurement scale, and the connection mode with the A port of the three-way valve (I) 1 is a detachable connection, and is used for alternately injecting the activation liquid methanol and the elution liquid N-methylpyrrolidone.

[0023] The inlet of the solid-phase extraction column 2 is connected to the B port located below the three-way valve (I) 1 through a pipeline. The solid-phase extraction column 2 is filled with an adsorption packing 3 for adsorbing benzene. Among them, the adsorption packing 3 is Tenax TA (GC grade, Tianjin Guangfu Fine Chemical Research Institute).

[0024] The gas sample tank 5 filled with carbon dioxide is connected to the C port through a gas distribution pipe. A gas flow control valve 9 is provided on the gas distribution pipe connecting the gas sample tank 5 and the C port of the three-way valve (I) 1.

[0025] The three-way valve (II) 4 is provided with three ports D, E, and F. The D port is connected to the outlet of the solid-phase extraction column 2 located above it through a pipeline. The E port is connected to the waste liquid bottle 6 through a pipeline. The F port is connected to the sample collection bottle 8 through a pipeline. Further, a conduit 7 extending to the bottom of the bottle is provided in the waste liquid bottle 6. The end of the conduit 7 is a beveled opening. The waste liquid bottle 6 can reserve sodium hydroxide solution capable of submerging the beveled end of the conduit 7, which is convenient for verifying whether the gas in the gas sample tank 5 has been discharged completely and can also be used to absorb carbon dioxide.

[0026] As Figure 2 shown, the working process of this embodiment includes the following steps:

[0027] S1 Activation: Rotate the three-way valve (I) 1 to connect the A and B ports, and at the same time rotate the three-way valve (II) 4 to connect to the D and E ports; Use a syringe 10 to draw 5 ml of methanol and inject it into the solid-phase extraction column 2 through the A port at a constant speed to activate the adsorption packing 3 (Tenax TA) in the solid-phase extraction column. The waste liquid after activation flows into the waste liquid bottle 6 through the DE ports, pipelines, and conduits 7 respectively;

[0028] S2 Sampling: Rotate the three-way valve (I) 1 to connect the C and B ports, and keep the three-way valve (II) 4 connected to the D and E ports unchanged. If the activation waste liquid does not submerge the bottom beveled opening of the conduit 7, an appropriate amount of sodium hydroxide solution can be added to completely submerge the bottom bevel of the conduit 7 under the liquid level; Open the switch of the gas sample tank 5 to release the carbon dioxide gas sample, and the gas flow control valve 9 can be used to control the injection into the solid-phase extraction column 2 at a speed of 2 L / min through the gas distribution pipe, C, and B ports. The activated adsorption packing 3 (Tenax TA) is used to adsorb and collect benzene in the gas. The adsorbed carbon dioxide gas flows into the waste liquid bottle 6 through the D and E ports and the conduit 7 respectively, and is absorbed by the sodium hydroxide solution therein or discharged from the bottle mouth until the carbon dioxide in the gas sample tank 5 is released completely or reaches the target amount and the switch of the gas sample tank 5 is closed. It can be further determined that the sampling is over by observing whether there are bubbles at the bottom of the conduit 7, which is convenient for judging whether to start the next operation;

[0029] S3 Elution: Rotate the three-way valve (I) 1 to connect ports A and B, and at the same time rotate the three-way valve (II) 4 to connect ports D and F. Use a syringe 10 to extract 10 ml of N-methylpyrrolidone solution and inject it evenly through port A into the solid-phase extraction column 2. Use N-methylpyrrolidone to elute benzene adsorbed in the adsorption filler 3 (Tenax TA). The eluate containing benzene is collected through ports D and F into the sample bottle 11 via a pipeline. Repeat the whole step 2 times to achieve stepwise elution of 20 ml of N-methylpyrrolidone;

[0030] S4 Volume Fixing: Collect the eluate in the above sample bottle, fix the volume to 20 ml with N-methylpyrrolidone, accurately measure 10 ml, transfer it to a headspace vial, tightly stopper it, and transfer it to a gas chromatograph for detection and analysis.

[0031] Example 2

[0032] As Figure 1 shown, an enrichment device for determining trace benzene in common gases includes a three-way valve (I) 1, a syringe 10, a solid-phase extraction column 2, a gas sample tank 5, a three-way valve (II) 4, a waste liquid bottle 6, and a sample collection bottle 8.

[0033] The three-way valve (I) 1 is provided with three ports A, B, and C. The syringe 10 is connected to port A above the three-way valve (I) 1. The syringe 10 has a measurement scale and is detachably connected to port A of the three-way valve (I) 1 for alternately injecting the activation liquid methanol and the elution liquid N-methylpyrrolidone.

[0034] The inlet of the solid-phase extraction column 2 is connected to port B below the three-way valve (I) 1 through a pipeline. The solid-phase extraction column 2 is filled with an adsorption filler 3 for adsorbing benzene. Among them, the adsorption filler 3 is Tenax TA (GC grade, Tianjin Guangfu Fine Chemical Research Institute).

[0035] The gas sample tank 5 filled with nitrogen is connected to port C through a gas distribution pipe. A gas flow control valve 9 is provided on the gas distribution pipe connecting the gas sample tank 5 and port C of the three-way valve (I) 1.

[0036] The three-way valve (II) 4 is provided with three ports D, E, and F. Port D is connected to the outlet of the solid-phase extraction column 2 above it through a pipeline. Port E is connected to the waste liquid bottle 6 through a pipeline. Port F is connected to the sample collection bottle 8 through a pipeline. Further, a conduit 7 extending to the bottom of the bottle is provided in the waste liquid bottle 6. The end of the conduit 7 is a beveled opening. The waste liquid bottle 6 can reserve water that can submerge the beveled opening at the end of the conduit 7, which is convenient for verifying whether the gas in the gas sample tank 5 has been exhausted.

[0037] As Figure 2 shown, the working process of this example includes the following steps:

[0038] Activation of S1: Rotate the three-way valve (I) 1 to connect ports A and B, and at the same time rotate the three-way valve (II) 4 to connect to ports D and E; Use a syringe 10 to extract 5 ml of methanol and inject it evenly through port A into the solid-phase extraction column 2 to activate the adsorption packing 3 (Tenax TA) in the solid-phase extraction column. The waste liquid after activation flows into the waste liquid bottle 6 through ports DE, pipelines, and conduits 7 respectively;

[0039] Sample loading of S2: Rotate the three-way valve (I) 1 to connect ports C and B, and at the same time keep the three-way valve (II) 4 connected to ports D and E unchanged. If the activation waste liquid does not submerge the bottom inclined plane of the conduit 7, appropriate water can be added to completely submerge the bottom inclined plane of the conduit 7 under the liquid level; Open the switch of the gas sample tank 5 to release the nitrogen sample. The gas flow control valve 9 can be used to control the injection into the solid-phase extraction column 2 at a speed of 2 L / min through the gas distribution pipe and ports CB. The activated adsorption packing 3 (Tenax TA) is used to adsorb and collect benzene in the gas. The nitrogen gas after adsorption flows into the waste liquid bottle 6 through ports DE and conduit 7 and is discharged outside from the bottle mouth. Until the nitrogen gas in the gas sample tank 5 is released completely or reaches the target amount, close the switch of the gas sample tank 5. Whether the sample loading is completed can be further determined by observing whether there are bubbles at the bottom of the conduit 7, which is convenient for judging whether to start the next operation;

[0040] Elution of S3: Rotate the three-way valve (I) 1 to connect ports A and B, and at the same time rotate the three-way valve (II) 4 to connect to ports D and F. Use a syringe 10 to extract 10 ml of N-methylpyrrolidone solution and inject it evenly through port A into the solid-phase extraction column 2. Use N-methylpyrrolidone to elute the benzene adsorbed on the adsorption packing 3 (Tenax TA). The eluate containing benzene is collected through ports D and F via pipelines into the sample bottle 11. Repeat the whole step 2 times to achieve the stepwise elution of 20 ml of N-methylpyrrolidone;

[0041] Volume fixing of S4: Collect the eluate in the above sample bottle, fix the volume to 20 ml with N-methylpyrrolidone, accurately measure 10 ml, transfer it to a headspace bottle, tightly stopper it, and transfer it to a gas chromatograph for detection and analysis.

[0042] Experimental example

[0043] Experimental materials: Carbon dioxide-containing gas cylinders (purchased from Xi'an Shenlan Low Temperature Energy Co., Ltd.), nitrogen-containing gas cylinders (purchased from Xi'an Shenlan Low Temperature Energy Co., Ltd.)

[0044] Experimental instruments: The present utility model is as Figure 1The devices shown, Tenax GR adsorption tubes (purchased from Beijing Green Grass Technology Development Co., Ltd.), Tenax-TA adsorbents (purchased from Tianjin Guangfu Fine Chemical Research Institute), benzene standard gas substance (content 50 μL / L), thermal desorption instrument (model TurboMatrix 350), gas chromatography-mass spectrometry instrument (model Clarus SQ 8), gas chromatograph (model Agilent 7890B).

[0045] Experimental method: Appropriate amount of benzene standard gas substance was taken and gradually diluted with carbon dioxide gas or nitrogen gas to prepare benzene standard carbon dioxide gas containing 0.02 μL / L or benzene standard nitrogen gas containing 0.02 μL / L.

[0046] Experimental group 1: The device and method of Example 1 were used to enrich 25 L of pre-prepared benzene standard carbon dioxide gas containing 0.02 μL / L, and 6 samples were processed in parallel to obtain samples 1 - 6 of experimental group 1, and they were detected by a gas chromatograph. The detection results are shown in Table 1;

[0047] Table 1: Repeatability of benzene measurement in carbon dioxide of experimental group 1 (content: μL / L)

[0048] Serial number Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Mean value RSD(%) Tenax-TA 0.0203 0.0211 0.0205 0.0215 0.0208 0.0207 0.0208 2.07

[0049] Control group 1: Referring to the detection method disclosed in "Determination of Ultra-Low Content Benzene in Food-Grade Carbon Dioxide by Enrichment Sampling Method" by Dong Yi et al. (Low Temperature and Specialty Gases, Vol. 41, No. 5, October 2023), 300 ml of benzene standard carbon dioxide gas containing 0.02 μL / L was taken and injected into a Tenax-TA adsorption tube to adsorb benzene in carbon dioxide. After adsorption, high-temperature desorption was carried out using a thermal desorption instrument respectively. 6 samples were processed in parallel to obtain samples 1 - 6 of control group 1, and they were detected by a gas chromatography-mass spectrometry instrument. The detection results are shown in Table 2;

[0050] Table 2: Repeatability of benzene measurement in carbon dioxide of control group 1 (content: μL / L)

[0051] Serial number Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Mean value RSD(%) Tenax-GR tube 0.0196 0.0186 0.0172 0.0179 0.0186 0.0206 0.0188 6.45

[0052] Experimental group 2: The device and method of Example 2 were used to enrich 25 L of pre-prepared benzene standard nitrogen gas containing 0.02 μL / L, and 6 samples were processed in parallel to obtain samples 1 - 6 of experimental group 2, and they were detected by a gas chromatograph. The detection results are shown in Table 3;

[0053] Table 3: Repeatability of benzene measurement in nitrogen of experimental group 2 (content: μL / L)

[0054] Serial number Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Mean value RSD(%) Tenax-TA 0.0224 0.0206 0.0213 0.0220 0.0216 0.0204 0.0214 3.65

[0055] Control Group 2: Referring to the detection method disclosed in "Determination of Ultra-low Content Benzene in Food-grade Carbon Dioxide by Enrichment Sampling Method" by Dong Yi et al. (Low Temperature and Special Gases, Vol. 41, No. 5, October 2023), 300 ml of a benzene standard nitrogen gas containing 0.02 μL / L benzene was taken and injected into a Tenax-TA adsorption tube to adsorb benzene in the nitrogen. After the adsorption was completed, high-temperature desorption was carried out using a thermal desorption instrument respectively. Six samples were processed in parallel to obtain Samples 1-6 of Control Group 2, and they were detected by a gas chromatography-mass spectrometer. The detection results are shown in Table 4;

[0056] Table 4: Repeatability of Benzene Measurement in Nitrogen of Control Group 2 (Content: μL / L)

[0057] Serial number Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Mean value RSD(%) Tenax-GR tube 0.0202 0.0182 0.0174 0.0178 0.0192 0.0168 0.0183 6.81

[0058] Conclusion: From the results in Tables 1-4, it can be seen that compared with the large-scale instruments of the prior art, the present utility model is not only simple in structure, low in cost, easy to assemble and operate, and does not require expensive thermal desorption instruments and special gas samplers, but also has better accuracy and repeatability of the detection results. This is because the prior art adopts the principle of "low-temperature adsorption - high-temperature desorption", and there is loss of gas during the high-temperature desorption process, which leads to lower accuracy and repeatability results than those of the present utility model.

[0059] The above shows and describes the basic principles, main features and advantages of the present utility model, and is not used to limit the present utility model. Any modification, equivalent change and decoration based on the technical essence of the present utility model for the above examples still fall within the scope of the technical solution of the present utility model.

Claims

1. An enrichment device for measuring trace benzene in common gases, characterized in that: The invention comprises a three-way valve I (1), a liquid injector (10), a solid phase extraction column (2), a gas sample tank (5), a three-way valve II (4), a waste liquid bottle (6) and a sample collection bottle (8). The three-way valve I (1) is provided with three ports A, B and C. The liquid injector (10) is connected to the port A above the three-way valve I (1) for injecting an activation liquid and an eluent. The inlet of the solid phase extraction column (2) is connected to the port B below the three-way valve I (1) through a pipeline. The solid phase extraction column (2) is provided with an adsorption filler (3) for adsorbing benzene. The gas sample tank (5) is connected to the port C through a gas distribution pipe. The three-way valve II (4) is provided with three ports D, E and F. The port D is connected to the outlet of the solid phase extraction column (2) located above it through a pipeline. The port E is connected to the waste liquid bottle (6) through a pipeline. The port F is connected to the sample collection bottle (8) through a pipeline.

2. The enrichment device according to claim 1, characterized in that The adsorption filler (3) is Tenax TA.

3. The enrichment device according to claim 1, characterized in that A gas flow control valve (9) is provided on the gas distribution pipe connecting the gas sample tank (5) and the C port of the three-way valve I (1).

4. The enrichment device according to claim 1, characterized in that The liquid injector (10) has a measuring scale and is connected to the A port of the three-way valve I (1) in a detachable manner.

5. The enrichment device according to claim 1, characterized in that The waste liquid bottle (6) is provided with a conduit (7) extending to the bottom of the bottle, and the end of the conduit (7) is a beveled opening.

6. The enrichment device according to claim 1, characterized in that The gas in the gas sample tank (5) includes but is not limited to carbon dioxide or an inert gas.

7. The enrichment device according to claim 1, characterized in that The activation solution and the eluent are methanol and N-methylpyrrolidone respectively.

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