A test method for evaluating the performance of dehumidification sealing drying tubes

Abstract

This invention belongs to the field of analytical chemistry instruments, specifically relating to a method for testing the performance of a dehumidifying and sealing drying tube used in an ion mobility spectrometer. The method involves using a dew point meter to test that the relative humidity of the drying tube is less than 2%, a pressure gauge to test the airtightness of the drying tube, and an ion mobility spectrometer to detect the background signal of the drying tube. This invention provides a simple and easy-to-implement method for testing the performance of a dehumidifying and sealing drying tube, accurately quantifying the relative humidity, sealing performance, and background signal of the drying tube to confirm whether a newly assembled or used drying tube meets the usage standards.

Description

Technical Field

[0001] This invention belongs to the field of analytical chemistry instruments, specifically relating to a method for testing the performance of a dehumidified and sealed drying tube used in an ion mobility spectrometer. Background Technology

[0002] Ion mobility spectrometers require clean air with extremely low moisture content to operate. The drying tube is filled with dehydrating particles such as molecular sieves and silica gel, which adsorb and remove moisture from the air to obtain clean air with very low moisture content. The sealing performance of the drying tube affects the effectiveness of moisture adsorption and removal; therefore, it is necessary to test the performance of the dehumidifying and sealing drying tube used in ion mobility spectrometers.

[0003] Jiang Ning et al. invented a high-sealing, high-efficiency drying tube for gas chromatography (patent number ZL201721392686.9), comprising a tube body with an air inlet machined on its lower surface and a top cover threadedly connected to the upper opening. The top cover has an air outlet. Three layers of circular mesh sheets distributed axially are detachably installed inside the tube body. The air inlet is integrally formed with the bottom of the drying tube, and the air outlet is integrally formed with the top cover. A rubber gasket is placed between the top cover and the drying tube, and the threaded connection between the top cover and the drying tube reduces leakage and achieves high sealing performance. The connection between the tube body and the top cover is achieved through the rubber gasket between the top cover and the upper opening of the tube body. If this rubber gasket is a sealing ring, it is prone to detachment during installation and disassembly; if it is a rubber sealing gasket, the area of ​​the sealing gasket is larger than that of a sealing ring, and the rubber will release or adsorb more organic matter in the gas, affecting the cleanliness of the treated gas and thus the analytical effect of the instrument. This patent does not cover the detection of high-sealing, high-efficiency drying tubes for gas chromatography.

[0004] The disposable drying tube invented by Li Jinghua et al. (patent number ZL201520864317.X) includes a shell (1), a shell end cap (2), and a desiccant (3). The shell (1) is filled with the desiccant (3). At the air inlet and outlet on the lower end face of the shell, there are hollow cylindrical interfaces with openings at both ends, protruding downwards. The air inlet and outlet are coaxial with their corresponding cylindrical interfaces. The shell end cap is fastened to the open end of the cylindrical shell. The desiccant is evenly filled into two chambers inside the cylindrical shell. The open end of the cylindrical shell is bonded and sealed to the shell end cap, forming a disposable drying tube. This drying tube has good sealing performance, is easy to assemble, and is easy to use. This patent does not mention the testing of the drying tube.

[0005] Zhu Meng et al. invented a hydrogen drying tube (patent number ZL201821714536.X), comprising a hollow cylindrical transparent tube. One end of the transparent tube has a sealing plug, which has an outlet and an inlet. The outlet is connected to an outlet pipe located inside the transparent tube. The sealing plug has a leak-proof cotton layer to prevent gas leakage from the transparent tube. The leak-proof cotton layer has a reactant layer that can react with oxygen, and the reactant layer has an absorbent cotton layer for absorbing moisture. The outlet pipe passes sequentially through the leak-proof cotton layer, the reactant layer, and the absorbent cotton layer. The sealing plug and leak-proof cotton layer provide a sealing function to prevent gas leakage from the transparent tube. The gas material should be rubber, silicone rubber, etc., which have elastic sealing functions. Rubber and silicone rubber release or absorb organic matter in the gas, affecting the cleanliness of the gas being processed and thus affecting the analytical results of the instrument. This patent relates to the sealing performance of a hydrogen drying tube, but not to its detection.

[0006] To address the issues of screening for leaking air due to unsealed drying tubes, insufficient cleanliness of drying tube materials, difficulty in confirming failure effects after moisture absorption, and confirmation of purging pretreatment effects, this invention provides a performance testing method for dehumidified and sealed drying tubes used in ion mobility spectrometers. This method plans to test the performance of drying tubes from different angles and using different technical means. The drying tubes have the characteristics of good sealing performance, easy identification of failure, and high gas source cleanliness, making them suitable for providing clean, low-humidity gas for ion mobility spectrometers. Summary of the Invention

[0007] This invention provides a test method for the performance of a dehumidifying and sealing drying tube, used to screen whether the drying tube is leaking, the cleanliness of the drying tube material, whether the drying tube fails after absorbing moisture, and the effect of purging pretreatment on the drying tube.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0009] This invention provides a testing method for the performance of a dehumidifying and sealing drying tube. The method tests the humidity, airtightness, and cleanliness of the drying tube. The relative humidity of the drying tube is less than 2%, and the gas pressure drop in the drying tube within 1 minute is less than 5 kPa.

[0010] In the above technical solution, the humidity is further detected by a dew point meter. The gas passes through a drying tube and is tested by the dew point meter to determine whether the relative humidity is less than 2%.

[0011] In the above technical solution, the airtightness is further tested by a pressure gauge. One end of the drying tube has two through holes, one of which is sealed, and the other is connected to a pressure gauge and an external air supply source, which supplies air to the drying tube.

[0012] In the above technical solution, an external gas source supplies gas at a pressure of 120-150 kPa to the drying tube, and records the gas pressure drop within 1 minute.

[0013] In the above technical solution, the ion mobility spectrum is further described by a negative high-voltage mode photoionization ion mobility spectrometer for detecting the cleanliness of the drying tube.

[0014] In the above technical solution, the cleanliness is further determined by an ion mobility spectrometer to detect whether there is a new background signal, or if there is no new signal, the signal reduction is less than 10%.

[0015] In the above technical solution, the drying tube is further connected in series in the carrier gas and drift gas paths of the ion mobility spectrometer to detect the acetone reagent ion peak of the analyzer, to detect whether there is a new signal, or to compare the acetone reagent ion peak with that before the drying tube is connected in series to examine the range of signal reduction.

[0016] Compared with existing technologies, the advantages of this invention are as follows: The method for testing the performance of the dehumidifying and sealing drying tube is simple and easy to implement. It can accurately quantify and detect the relative humidity, sealing performance, and background signal of the drying tube to confirm whether newly assembled or used drying tubes meet the usage standards. After testing, the drying tube is used in an ion mobility spectrometer, avoiding contamination of the detector's ion mobility tube by unclean gas sources. Since the dehumidifying and sealing drying tube meets cleanliness requirements after testing, the analyzer can be used directly for qualitative and quantitative analysis of samples without system purging. Attached Figure Description

[0017] Figure 1 Background signal of ion mobility spectrometer (acetone-air reagent ion peak);

[0018] Figure 2 Ion migration spectra detected in IMS carrier gas after 1 day of purging of the drying tube;

[0019] Figure 3 Ion mobility spectra detected in IMS drift gas after 1 day of purging of the drying tube;

[0020] Figure 4 Ion migration spectra detected in IMS carrier gas after 3 days of purging of the drying tube;

[0021] Figure 5 Ion migration spectra detected in IMS drift gas after 3 days of purging of the drying tube. Detailed Implementation

[0022] The present invention will be further described below with reference to specific embodiments, but this does not limit the present invention in any way.

[0023] Example 1

[0024] Select three drying tubes that have passed pressure testing and meet the standards. One of them is newly filled with molecular sieve, and the other two are used on the ion mobility spectrometer production line.

[0025] The pressure test method is as follows: There are two through holes at one end of the sealed drying tube. The two through holes are connected to quick connectors respectively. One connector is connected to a plug, and the other connector is connected to a pressure gauge and an external air supply in sequence. The external air supply supplies air to the drying tube, so that the gas pressure in the drying tube is 120-150 kPa. If the gas pressure drop is less than 5 kPa within 1 minute, the sealing performance is good.

[0026] One stream of clean air was passed through three drying tubes, and then the relative humidity was measured sequentially by a dew point meter. The relative humidity of the newly installed drying tube was 0.1%; the relative humidity of the other two tubes was 0.11% and 2.3%, respectively. The drying tube with a relative humidity of 2.3% should be replaced.

[0027] Example 2

[0028] A newly assembled drying tube was used. The hollow cylinder contained granular desiccant, which was a molecular sieve, used to adsorb and remove moisture from the gas. The drying tube was tested for sealing performance at a gas pressure of 145 kPa. After 1 minute, the gas pressure remained at 142 kPa. A gas pressure drop of 3 kPa met the sealing performance requirements of the drying tube.

[0029] Example 3

[0030] Background signal in the drying tube was detected using a photoionization ion mobility spectrometer in negative high-voltage mode. Detection conditions: migration tube temperature 120℃, thermal desorption injector temperature 150℃, bleaching gas 600 sccm, carrier gas 300 sccm. First, the acetone-air reagent ion peak of the ion mobility spectrometer was recorded, such as... Figure 1 As shown.

[0031] After ion mobility spectrometry detection, only the gas with the air reagent ion peak is used to purge the drying tube at a flow rate of 1-3 L / min and a pressure of 0.1-0.3 MPa.

[0032] After purging the newly assembled drying tube for one day, it was connected in series in the carrier gas path of the ion mobility spectrometer to detect the acetone reagent ion peak; the detection results are as follows. Figure 2 As shown.

[0033] After purging the newly assembled drying tube for one day, it was connected in series in the drift gas path of the ion mobility spectrometer to detect the acetone reagent ion peak; the detection results are as follows. Figure 3 As shown.

[0034] After purging the newly assembled drying tube for 3 days, it was connected in series in the carrier gas path of the ion mobility spectrometer to detect the acetone reagent ion peak; the detection results are as follows. Figure 4 As shown.

[0035] After purging the newly assembled drying tube for 3 days, it was connected in series in the drift gas path of the ion mobility spectrometer to detect the acetone reagent ion peak; the detection results are as follows. Figure 5 As shown.

[0036] Figure 2 and Figure 3 Spectrum and Figure 1 The signal is lower than expected, indicating that the cleanliness level does not meet the requirements, and purging needs to continue. Figure 4 and Figure 5 Spectrum and Figure 1 In comparison, no new impurity peak signals were added, and the acetone reagent ion peak signal was reduced to within 1000mV, less than 10%, compared with that before the tandem drying tube. Therefore, the drying tube is considered to meet the standard and can be used.

[0037] For anyone skilled in the art, many possible variations and modifications can be made to the technical solutions of this invention, or equivalent embodiments can be modified based on the disclosed technical content, without departing from the scope of the technical solutions of this invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this invention without departing from the content of the technical solutions of this invention should still fall within the protection scope of the technical solutions of this invention.

Claims

1. A method for testing the performance of a dehumidifying sealed drying tube, characterized in that: The method measures the humidity, airtightness, and cleanliness of the drying tube; the relative humidity of the drying tube is less than 2%, and the gas pressure drop in the drying tube within 1 minute is less than 5 kPa. Ion mobility spectrometry is performed using a negative high-voltage mode photoionization ion mobility spectrometer to detect the cleanliness of the drying tube. The cleanliness level is determined by an ion mobility spectrometer to detect whether there is a new increase in background signal, or if there is no new signal and the signal decrease is less than 10%.

2. The method for testing the performance of a dehumidifying sealed drying tube according to claim 1, characterized in that: The humidity is detected by a dew point meter. The gas passes through a drying tube and is tested by the dew point meter to determine whether the relative humidity is less than 2%.

3. The method for testing the performance of a dehumidifying sealed drying tube according to claim 1, characterized in that: The airtightness is tested by a pressure gauge. One end of the drying tube has two through holes. One through hole is sealed, and the other through hole is connected to a pressure gauge and an external air supply source, which supplies air to the drying tube.

4. A method for testing the performance of a dehumidifying sealed drying tube according to claim 1 or 3, characterized in that: An external gas supply source provides gas at a pressure of 120-150 kPa to the drying tube, and the gas pressure drop value within 1 minute is recorded.

5. The method for testing the performance of a dehumidifying sealed drying tube according to claim 1, characterized in that, The drying tubes are connected in series in the carrier gas and drift gas paths of the ion mobility spectrometer to detect the acetone reagent ion peak of the analyzer, to detect whether there is a new signal, or to compare the acetone reagent ion peak with that before the drying tubes are connected in series to examine the range of signal reduction.

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