Organic matter adsorption detection method based on MOF

Abstract

The invention provides an organic matter adsorption detection method based on MOF, and relates to the technical field of testing or analyzing materials by means of measuring chemical or physical properties of the materials, the detection method comprises the following steps: activating an obtained MOF material; a Teflon tube is filled with the activated MOF material, and an adsorption tube containing the MOF material is prepared; the adsorption pipe is connected to the rear end of the ventilation pipeline containing the standard substance in the internal gas flowing direction; n2 is input to purge the ventilation pipeline, and the standard substance is purged into the adsorption pipe; carrying out desorption on the adsorbed MOF material to generate a gaseous sample, and carrying out GC-MS detection on the gaseous sample to obtain detection data; by adopting the detection method disclosed by the invention, the adsorption capacity of the MOF material on various VOCs substances can be detected, so that the VOCs exhaled by a human body can be enriched when the VOCs exhaled by the human body are detected, and the problems that the content of the VOCs in the exhaled air of the human body is relatively low and the VOCs are difficult to be directly detected by an instrument are effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of metabolite testing and analysis, and more specifically, to an organic matter adsorption detection method based on MOF. Background Art

[0002] Mass spectrometry is a technology that tests and analyzes materials by measuring their chemical or physical properties. It is usually used to detect the m / z of a substance to analyze its properties and categories. The detection of VOCs (volatile organic compounds) in human breath is of great significance for the assessment of human health and athletic ability, but the detection of VOCs can usually only be done by online detection methods that obtain test samples in real time, which is very inconvenient for both the test population and the test process. In addition, the content of many VOCs in human breath is low (ppt-ppb level), which is difficult to be directly detected by instruments. The current detection methods of exhaled VOCs include online detection and offline detection. Online detection such as SESI-MS (Secondary Electrospray Ionization Mass Spectrometry), SIFT-MS (Selected Ion Flow Tube Mass Spectrometry), and PTR-MS (Proton Transfer Reaction Mass Spectrometry) lack chromatographic separation, making it difficult to accurately identify VOCs. Therefore, how to effectively sample, transport and detect VOCs in human exhaled breath in a more comprehensive and convenient way has become a current research hotspot. Summary of the invention

[0003] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a MOF-based organic matter adsorption detection method to overcome the shortcomings of the prior art that the VOCs content in human exhaled breath is low and difficult to be directly detected by instruments.

[0004] The above technical objectives of the present invention are achieved through the following technical solutions: A method for detecting organic matter adsorption based on MOF, comprising: S1: Activate the obtained MOF material; S2: filling the activated MOF material into a Teflon tube to prepare an adsorption tube containing the MOF material; S3: connecting the adsorption tube to the rear end of the ventilation pipeline containing the standard along the internal gas flow direction; S4: Input N2 to purge the ventilation pipeline, and purge the standard into the adsorption tube; S5: Desorbing the adsorbed MOF material to generate a gaseous sample, extracting the gaseous sample with an SPME probe, and performing GC-MS detection on the extracted SPME probe to obtain detection data.

[0005] In one embodiment, the MOF material is specifically MIL-101(Cr).

[0006] In one embodiment, the activation of the obtained MOF material specifically includes: placing the obtained MIL-101(Cr) at 150° C. for vacuum activation for 12 h.

[0007] In one embodiment, after filling the activated MOF material into the Teflon tube, the method further includes: filling glass wool at both ends of the Teflon tube; and preparing an adsorption tube containing the MOF material.

[0008] In one embodiment, filling the activated MOF material into a Teflon tube specifically includes: filling 100 mg of the activated MOF material into a Teflon tube to prepare an adsorption tube.

[0009] In one embodiment, the inputting N2 to purge the ventilation line to purge the standard into the adsorption tube specifically includes: inputting N2 to purge the ventilation line at a flow rate of 0.5 L / min to purge the standard into the adsorption tube until the standard in the ventilation line is completely volatilized.

[0010] In one embodiment, the standard substance is one or more of the following substances: Acetone, indole, p-cresol, propionic acid, octanal, butyraldehyde, heptaldehyde, butyric acid, phenol, 2-phenylethylamine, malic acid and DMSO.

[0011] In one embodiment, desorbing the adsorbed MOF material to generate a gaseous sample specifically includes: transferring the adsorbed MOF material to a headspace bottle, and heating it in an oil bath at 150° for 10 minutes to generate a gaseous sample.

[0012] In one embodiment, the extracting of the gaseous sample by an SPME probe and performing GC-MS detection on the extracted SPME probe to obtain detection data specifically includes: Inserting the SPME probe into the headspace bottle to extract the gaseous sample in the headspace bottle for 5 minutes, and performing GC-MS detection on the extracted SPME probe to obtain detection data; The material of the SPME probe is specifically: quartz fiber and / or StableFlex fiber; The quartz fiber is coated with a Polyacrylate coating; The StableFlex fiber is coated with one or more of a PDMS coating, a DVB coating, and a CAR coating.

[0013] In one embodiment, the step of performing GC-MS detection on the extracted SPME probe to obtain detection data specifically includes: inserting the extracted SPME probe into a chromatographic device to perform chromatographic separation on the VOCs extracted by the SPME probe; The VOCs separated by the chromatography are input into the mass spectrometer one by one to obtain the detection data.

[0014] In one embodiment, the parameters of the chromatographic device are specifically: The specific chromatographic column model is: HP-5MS; The temperature of the chromatographic column is specifically controlled by the following steps: the column temperature is 35°C for 2 minutes; then the temperature is raised to 150°C at a rate of 8°C / min and maintained at 150°C for 1 minute; then the temperature is raised to 250°C at a rate of 50°C / min and maintained at 250°C for 2 minutes. The total operating time is 21.375 minutes. Flow rate: 0.8 mL / min; Inlet parameters: temperature: 250°C; pressure: 9.8 psi; purge flow: 3 mL / min, split ratio 0-20:1.

[0015] In one embodiment, the parameters of the mass spectrometer are specifically: Ion source type: EI; Scan type: full scan; Scan range: 40-450 Da; Scan speed: 1562 u / s; Scanning frequency: 3.6 Da / s; Cycle time: 285.04 ms.

[0016] In one embodiment, before step S1, the method further includes: Use N2 to purge the standard product to form a standard gas sample; directly use an SPME probe to extract the standard gas sample at the outlet of the ventilation pipeline for 1-2 minutes; wherein no adsorption tube is provided on the ventilation pipeline; The extracted SPME probe is subjected to GC-MS detection to generate standard test results; Based on the standard detection result, it is determined whether the standard product can be purged by N2 to form VOCs gas. If so, step S1 is executed.

[0017] Beneficial Effects The present invention provides a method for detecting organic matter adsorption based on MOF, comprising: activating an acquired MOF material; filling a Teflon tube with the activated MOF material to prepare an adsorption tube containing the MOF material; connecting the adsorption tube to the rear end of a ventilation pipeline containing a standard substance along the internal gas flow direction; inputting N2 to purge the ventilation pipeline to purge the standard substance into the adsorption tube; desorbing the adsorbed MOF material to generate a gaseous sample, and performing GC-MS detection on the gaseous sample to obtain detection data; adopting the detection method of the present application, the adsorption capacity of the MOF material for various VOCs substances can be detected, so that when detecting VOCs in human exhaled breath, the VOCs exhaled by the human body can be enriched, and the problem that the content of VOCs in human exhaled breath is low and difficult to be directly detected by instruments is effectively solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a flow chart of a method for detecting organic matter adsorption based on MOF of the present invention; Figure 2 Schematic diagram of acetone detection results in an embodiment of the present invention; Figure 3 Schematic diagram of propionic acid detection results in an embodiment of the present invention; Figure 4 Schematic diagram of the detection result of octanal in an embodiment of the present invention; Figure 5 Schematic diagram of butyraldehyde detection results in an embodiment of the present invention; Figure 6 Schematic diagram of heptanal detection results in an embodiment of the present invention; Figure 7 Schematic diagram of butyric acid detection results in an embodiment of the present invention; Figure 8 Schematic diagram of phenol detection results in an embodiment of the present invention; Fig. 9 Schematic diagram of DMSO detection results in an embodiment of the present invention; Fig.10 Schematic diagram of indole detection results in an embodiment of the present invention; Fig.11 It is a schematic diagram of the detection result of p-cresol in an embodiment of the present invention; Fig.12 It is a schematic diagram of the detection result of 2-phenylethylamine in an embodiment of the present invention; Fig.13 Schematic diagram of malic acid detection results in an embodiment of the present invention. DETAILED DESCRIPTION

[0019] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings. Several embodiments of the present invention are shown in the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein.

[0020] The present invention is described in detail below in conjunction with the accompanying drawings and embodiments. In order to facilitate understanding of the embodiments, the related technology is first described. Offline detection mostly uses GC-MS (Gas Chromatography-Mass Spectrometry), but it requires the substances to be volatile and semi-volatile substances with thermal stability. Detection using LC-MS (Liquid Chromatography-Mass Spectrometry) has lower requirements on the properties of the substance and can detect more types.

[0021] The further role of studying the ability of MOF to adsorb exhaled VOCs is to use the adsorption of MOF on exhaled VOCs to enrich low-concentration exhaled VOCs in MOF adsorption tubes and conduct qualitative and quantitative analysis through LC-MS. In the future, MOF is expected to be used for sampling and pre-enrichment integrated exhaled air collection and storage.

[0022] Embodiment 1 In order to solve the above problems, the present invention provides a method for detecting organic matter adsorption based on MOF, such as Figure 1 As shown, including: S1: Activate the obtained MOF material; S2: filling the activated MOF material into a Teflon tube to prepare an adsorption tube containing the MOF material; S3: connecting the adsorption tube to the rear end of the ventilation pipeline containing the standard along the internal gas flow direction; S4: Input N2 to purge the ventilation pipeline and purge the standard into the adsorption tube; S5: Desorbing the adsorbed MOF material to generate a gaseous sample, extracting the gaseous sample with an SPME probe, and performing GC-MS detection on the extracted SPME probe to obtain detection data.

[0023] In practical applications, activation of MOF materials refers to the process of completely opening up the pore structure by removing the solvent or template molecules in the MOF pores, thereby maximizing its specific surface area and pore volume for use in applications such as adsorption and catalysis. Synthesized MOF materials usually have residual organic solvents, reactants or template molecules in their pores, which will block the pores and affect the adsorption performance of MOF. Therefore, removing these impurities through activation can allow the pore structure of MOF to fully exert its functionality and improve its adsorption capacity and the availability of active sites.

[0024] After the material is activated, it is filled into a Teflon tube to prepare an adsorption tube containing MOF material. Teflon has strong corrosion resistance and chemical stability to most chemicals, and can avoid chemical reactions with VOC or MOF materials, thereby reducing interference and ensuring the accuracy of detection; the surface of Teflon is very smooth and hydrophobic, and it is not easy to adsorb gas or volatile organic compounds (VOC). This means that during the detection process, Teflon will not adsorb VOCs in the sample, ensuring that all VOCs are adsorbed by the MOF material, improving the detection sensitivity; the surface of Teflon is smooth and has a low friction coefficient, which is convenient for the uniform filling and removal of MOF materials.

[0025] Connecting the adsorption tube to the rear end of the ventilation pipeline containing the standard means that when the adsorption tube is used to collect volatile VOCs, the adsorption tube needs to be located downstream of the standard during pipeline design. Only when the VOCs dissolved in the standard evaporate to form gas under the purge of N2 can they be absorbed by the adsorption tube located downstream.

[0026] In order to explore the adsorption capacity of MOF for various VOCs substances, after the MOF adsorption in the adsorption tube is completed, the VOCs adsorbed by MOF need to be detected to determine whether MOF has an adsorption effect on various VOCs, that is, to desorb the VOCs adsorbed by MOF. First, the MOF material in the Teflon tube is transferred out, and then the VOCs are desorbed from the MOF by certain desorption means, and the desorbed VOCs are tested by GC-MS to obtain the test data. Since MOF materials do not have an adsorption effect on all VOCs, the MOF after the adsorption step may not necessarily adsorb VOCs substances, and VOCs gas may not be generated after the desorption step. Regardless of whether there is an adsorption effect, the gas after the desorption step is collected, and the gas sample is tested by GC-MS (Gas Chromatography-Mass Spectrometry) to obtain the final test results. After obtaining the test results, by analyzing the test results, it can be determined whether the MOF material has an adsorption effect on this type of VOCs substance.

[0027] In this embodiment, the SPME probe is specifically used to extract the gaseous sample, and the extracted SPME probe is subjected to GC-MS detection to obtain detection data. Compared with the traditional nitrogen purge method, SPME can enrich low-concentration targets, which is particularly suitable for the analysis of VOCs (ppb or lower), and effectively improves the detection sensitivity. The background interference can be effectively reduced during the SPME extraction process, and the accuracy and reliability of the analysis can be improved. In addition, the traditional quadrupole mass spectrometer uses nitrogen purge to purge the gaseous sample into the mass spectrometry detection equipment, which may dilute the target compound and make it difficult to detect low-concentration components. In addition, since the gas sample exhaled by the human body contains a large amount of water vapor, this may affect the detection results of the mass spectrometer for the gaseous sample, and SPME is not affected by water vapor, which further improves the accuracy of the detection. The SPME probe is flexible in operation and can be applied to various scenarios such as laboratories, high-throughput screening and portable devices. It can be seamlessly integrated with a variety of detection devices. The nitrogen purge method is more suitable for laboratory fixed devices, and has poor portability and adaptability.

[0028] After the extraction is completed using the SPME probe, the extracted SPME probe needs to be tested by GC-MS. The GC part can first separate the different types of VOCs in the complex mixture, and then analyze the separated compounds through the mass spectrometer. When faced with a large number of different types of VOCs contained in exhaled breath (usually up to hundreds of types), GC-MS can effectively distinguish complex mixtures and reduce signal interference between components. Traditional quadrupole mass spectrometers usually analyze mixed gases directly, relying on a single mass-to-charge ratio ( m / z ) signals, which has low accuracy in qualitative analysis of compounds in complex mixtures and is easily interfered by other compounds in complex matrices, resulting in poor selectivity.

[0029] The detection method of the present application can detect the adsorption capacity of MOF materials for various VOCs substances, so that when detecting VOCs in human exhaled breath, the VOCs exhaled by the human body can be enriched, effectively solving the problem that the content of VOCs in human exhaled breath is low and difficult to be directly detected by instruments.

[0030] In one embodiment, the MOF material is specifically MIL-101(Cr).

[0031] In practical applications, MIL-101(Cr) is a metal organic framework (MOF) material based on chromium (Cr). This MOF has a very high specific surface area and porosity, and has good adsorption capacity for many gases and liquids. In addition, MIL-101(Cr) has two different sizes of microporous windows, which can adsorb VOCs of various molecular sizes. At the same time, MIL-101 (Cr) is not only simple to synthesize, but also easy to recycle and reuse, reducing the cost of use. Functionalized ligands can also be used in the synthesis process, or various chemical treatments can be performed on the coordination unsaturated points and organic ligands after synthesis, so as to facilitate the subsequent functional modification of MIL-101 (Cr) to further enhance its adsorption capacity for exhaled VOCs.

[0032] Human exhaled breath mainly contains hydrocarbons (aromatic compounds, aliphatic compounds) and oxygen-containing compounds (aldehydes, ketones, alcohols, etc.), among which acetone levels are increased in diabetic patients; propionic acid, butyraldehyde, heptanal, and octanal are exhaled breath markers for lung cancer; indole and p-cresol are biomarkers for chronic obstructive pulmonary disease; our research group found that butyric acid, propionic acid, butyraldehyde, heptanal, octanal, indole, and p-cresol are potential exhaled breath biomarkers for exercise monitoring; DMSO is a potential exhaled breath marker for chronic kidney disease (CKD). The benzene ring in the MIL-101 (Cr) ligand can enhance its adsorption of aromatic compounds, and there is a strong interaction between the unsaturated metal site as an electron acceptor and VOCs containing heteroatoms (butyric acid, propionic acid). MIL-101 (Cr) has an effective adsorption effect on compounds such as acetone and butanone. Moreover, MIL-101 (Cr) has a larger pore volume than other MOF materials, which provides more adsorption sites for the adsorption of VOCs, making its adsorption capacity of VOCs higher. Therefore, choosing MIL-101 (Cr) material for enrichment of exhaled VOCs can effectively enrich exhaled VOCs.

[0033] In one embodiment, activating the obtained MOF material specifically includes: placing the obtained MIL-101(Cr) at 150° C. for vacuum activation for 12 h.

[0034] In practical applications, the activation of MOF materials mainly includes heating activation, vacuum activation, solvent exchange activation and supercritical activation. In this application, MIL-101(Cr) material will absorb moisture in the air during storage, occupying the adsorption pores and adsorption sites of MOF, affecting its subsequent adsorption effect. The purpose of activation is to remove the adsorbed water molecules, so that it can obtain the largest pores and specific surface area, and enhance its adsorption capacity for VOCs.

[0035] In one embodiment, after filling the activated MOF material into the Teflon tube, the method further includes: filling glass wool at both ends of the Teflon tube; and preparing an adsorption tube containing the MOF material.

[0036] In practical applications, MOF materials themselves are usually porous crystal structures with small particles that are easily disturbed by airflow. Glass wool has good mechanical strength and can effectively fix MOF materials, preventing MOF particles from being blown away or displaced by airflow, and helping MOF materials to remain firmly in the tube. The fiber structure of glass wool helps to evenly distribute the airflow, thereby ensuring that the gas flowing through the MOF material can fully contact the MOF material. This uniform gas flow can improve the adsorption efficiency of VOCs, avoid excessive airflow speed or poor gas flow in local areas, and thus improve the overall adsorption performance. Glass wool can also serve as a buffer layer to reduce the mechanical impact of gas flow on MOF materials. Especially when operating at high flow rates, glass wool can effectively protect the structural integrity of the MOF material, thereby ensuring long-term adsorption performance and stability.

[0037] In one embodiment, filling the activated MOF material into a Teflon tube specifically includes: filling 100 mg of the activated MOF material into a Teflon tube to prepare an adsorption tube.

[0038] Specifically, by limiting the amount of MOF material used, it is possible to ensure that the amount of MOF used in each experiment is fixed, thereby controlling its adsorption capacity. The adsorption performance of MOF is usually closely related to its specific surface area, pore structure and material quality. Limiting the quality of the material can ensure that the amount of gas adsorbed in each experiment remains consistent, thereby improving the repeatability and reliability of the experiment. Standardizing the adsorption and desorption amounts of VOCs can make the experimental results more comparable and help evaluate the performance differences under different MOF materials or experimental conditions.

[0039] In one embodiment, N2 is input into the ventilation line to purge the standard into the adsorption tube, specifically comprising: inputting N2 into the ventilation line at a flow rate of 0.5 L / min to purge the standard into the adsorption tube until all the standard in the ventilation line is volatilized, and the purging time is maintained within 30 minutes by controlling the amount of standard added.

[0040] Use N2 to purge the ventilation line. Since a standard substance formed by a VOCs solution is also arranged in the ventilation line, during the N2 purge process, the gaseous VOCs formed by the volatilization of the standard substance can flow backward with the N2. After passing through the adsorption tube, the VOCs in the gas sample are adsorbed by the MOF to achieve VOCs enrichment.

[0041] In this embodiment, the flow rate of N2 purge needs to be adjusted based on the gas flow rate generated by human exhalation. A higher actual flow rate shortens the contact time between VOCs and MOF materials, thereby reducing adsorption performance; a lower flow rate will make the time required for enrichment too long. In addition, MOF materials are provided in the ventilation pipeline, which affects the flow of air. If the set flow rate is too high, the effort required for sampling is large; if the set flow rate is too low, the blowing time will be too long, which is not conducive to application.

[0042] In one embodiment, in order to determine whether the gas in the ventilation line is flowing, the end of the ventilation line can be placed in water or other liquids to observe whether bubbles emerge from the liquid. If so, there is gas flowing in the ventilation line.

[0043] In one embodiment, the adsorbed MOF material is desorbed to generate a gaseous sample, specifically comprising: transferring the adsorbed MOF material to a headspace bottle, and heating it in an oil bath at 150° C. for 10 minutes to generate a gaseous sample.

[0044] A headspace bottle is a container used to hold a solution sample and then analyze the gas sample in the top space of the bottle. The headspace technology analyzes the gas layer or the headspace above the sample in the sample bottle, rather than drawing the sample from the sample layer. Headspace analysis requires that the target compound is volatile, while the rest of the sample is not volatile or is a non-volatile substance. In this application, the use of an oil bath to heat the headspace bottle can desorb the VOCs adsorbed by the MOF material in the headspace bottle as much as possible and volatilize them into the space of the headspace bottle, so that the gaseous sample can be collected and analyzed in the next step.

[0045] In order to explore the appropriate desorption temperature of MOF materials, before the enrichment experiment, three temperatures of >300℃, 250℃ and 150℃ were selected to heat the MOF materials. The results showed that heating treatments of >300℃ and 250℃ would cause different degrees of color changes in the MOF materials, so 150℃ was selected for heating desorption.

[0046] In this embodiment, oil bath heating desorption is selected as the specific desorption method because heating desorption can be combined with SPME and GC-MS to detect VOCs adsorbed on MOF materials. The selection of heating desorption is also related to the characteristics of MOF. The MOF materials currently used have good thermal stability. The coordination bonds when adsorbing VOCs can be broken by heating, and the structure of the MOF material will not be destroyed, so that it can be reused. When using other MOF materials for adsorption and detection, other desorption methods can also be selected according to the characteristics of the MOF material and the characteristics of the adsorbed VOCs.

[0047] In one embodiment, the SPME probe is used to extract the gaseous sample, and the extracted SPME probe is subjected to GC-MS detection to obtain detection data, which specifically includes: inserting the SPME probe into the headspace bottle to extract the gaseous sample in the headspace bottle for 5 minutes, and the extracted SPME probe is subjected to GC-MS detection to obtain detection data; the material of the SPME probe is specifically: quartz fiber and / or StableFlex fiber; the quartz fiber is coated with Polyacrylate coating; the StableFlex fiber is coated with one or more of PDMS coating, DVB coating, and CAR coating. By selecting different coating materials (such as PDMS, DVB, etc.), selective enrichment of specific types of VOCs (such as acetone, aldehydes, ketones, etc.) can be achieved. The probe coating can shield the influence of interfering substances such as moisture and improve the selectivity of target compounds.

[0048] The Polyacrylate coated probe is suitable for the detection of propionic acid and butyric acid, the PDMS / DVB coated probe is suitable for the detection of butyraldehyde, octanal, heptanal, and malic acid, and the DVB / CAR / PDMS coated probe is suitable for the detection of acetone, indole, phenol, 2-phenylethylamine, p-cresol, and DMSO.

[0049] SPME (Solid Phase Microextraction) is a solvent-free sample preparation technique used to extract volatile and semi-volatile compounds from gas or liquid samples. The structure of the SPME probe includes a fiber coated with an adsorbent, which is fixed to a needle-shaped device. The adsorbent coating of the probe captures the target compounds in the sample, which are then analyzed in the GC-MS detection instrument. The nitrogen purge technology treats all volatile gases equally, and cannot distinguish between target and interferents, and high humidity conditions such as water vapor may interfere with the QMS signal.

[0050] GC-MS is a detection technology that combines gas chromatography (GC) with mass spectrometry (MS). Gas chromatography (GC) is used to separate compounds in a sample. The sample first enters the GC column. The chemical components in the column are separated according to different volatilities and polarities. Different compounds in the gas sample enter the mass spectrometer at different time periods. Mass spectrometry (MS) is used to identify and analyze the separated compounds. Mass spectrometry ionizes the compounds and measures the mass-to-charge ratio ( m / z ) to generate characteristic spectra, each compound will produce a unique mass spectrum. By comparing these spectra with the database, the specific compounds in the sample can be identified.

[0051] In this example, the SPME probe was exposed to the gaseous sample for 5 minutes to allow the adsorption layer on the probe surface to fully contact the volatile organic compounds (VOCs) in the sample. After 5 minutes of extraction, the adsorption layer on the probe absorbed some representative compounds in the sample; the SPME probe was inserted into the injection port of the GC-MS device, heated to desorb the compounds adsorbed on the probe from the adsorption layer, and entered the GC-MS system for separation and identification.

[0052] In the final test data, the relative content of each compound in the sample can be quantitatively analyzed through the peak area of ​​the gas chromatography part. Each compound produces a peak in the GC, and the concentration of the compound can be inferred from the height or area of ​​the peak.

[0053] In one embodiment, the method further comprises: aging the SPME probe in the injection port for 20 minutes before each adsorption.

[0054] In the previous test, the SPME probe may have adsorbed some compounds that were not completely desorbed. Aging can completely remove these residual substances by heating, ensuring that the results of this test are not interfered by the residues of the previous test. The cleaning and recovery process ensures that the probe has consistent adsorption capacity each time it is used, thereby improving the accuracy and repeatability of the test results.

[0055] The process of using the GC-MS system to detect the SPME probe includes: injecting the extracted SPME probe into the injection port for 5 minutes.

[0056] The heating time of the SPME probe injection port is controlled within 5 minutes to ensure that all target compounds on the probe can be completely desorbed and sent to the GC system to avoid signal loss or incomplete detection caused by incompletely desorbed compounds. Sufficient desorption can ensure that all target compounds in the sample are detected, thereby improving the sensitivity and accuracy of the data.

[0057] In one embodiment, due to the existence of some special VOCs, the properties of which cannot be detected by GC-MS, the present application also proposes a control test group, specifically including: Before step S1, the method further includes: Use N2 to purge the standard product to form a standard gas sample; use the SPME probe to directly extract the standard gas sample at the outlet of the ventilation pipeline for 1-2 minutes; no adsorption tube is set on the ventilation pipeline; The extracted SPME probe is subjected to GC-MS detection to generate standard test results; Based on the standard test results, it is determined whether the standard product can be purged by N2 to form VOCs gas. If so, step S1 is executed.

[0058] Specifically, before each use of MOF to enrich VOCs, nitrogen is first used to directly purge the standard, and then the SPME probe is placed at the end outlet of the ventilation line to directly extract the mixed gas formed by the purge. After extraction, the SPME probe is tested by GC-MS. If the target VOCs can be detected in this test result, it means that the VOCs can be detected by GC-MS. If this VOCs is not detected during the subsequent enrichment step, it means that this substance cannot be enriched by MOF. In addition, this control group can also verify whether the target VOCs can form a gas sample through nitrogen purge of the standard. If the VOCs in the standard can be purged by nitrogen to form volatile gases, then the nitrogen purge step can be ensured to be effective in actual detection; otherwise, other sample processing methods can be adopted. In this way, the sample pretreatment process can be adjusted according to the characteristics of different VOCs to improve the detection efficiency and accuracy. When it is confirmed that the target VOCs can be detected by GC-MS, if the VOCs are not detected in the subsequent MOF enrichment test, it can be judged that the problem lies in the insufficient adsorption efficiency of MOF for the VOCs, rather than defects in the detection instrument or pretreatment.

[0059] In one embodiment, two groups of blank controls are also included. One group is directly purged with N2 in the ventilation line without standards and MOF, and then the SPME probe is placed at the terminal outlet of the ventilation line for extraction, and then the SPME probe is detected by GC-MS.

[0060] This blank control can help determine whether the ventilation system and its components introduce any unwanted background impurities during the purge process, ensuring that the signal detected by GC-MS comes only from the standards introduced in subsequent experiments or VOCs adsorbed by MOF. If any VOCs or other impurity signals are detected in this control group, it indicates that there may be a source of contamination introduced by the device or the environment. In the actual experimental data processing, these background signals can be subtracted to ensure more accurate measurement results.

[0061] The other group used N2 to purge directly in the ventilation line without standards and only containing MOF, and then placed the SPME probe at the end outlet of the ventilation line for extraction, and then performed GC-MS detection on the SPME probe.

[0062] This blank control helps confirm whether the MOF material releases any of its own volatile impurities under nitrogen purge conditions, or whether there are other compounds that are automatically desorbed by the MOF material during the purge process, ensuring that the VOCs detected in subsequent experiments come from actual samples rather than spontaneous release of MOF. If a VOCs signal is detected in this control group, it may be volatiles released by the MOF material under specific conditions. By recording these signals, they can be excluded in subsequent analysis to ensure the purity of the data and avoid misjudgment of the MOF adsorption capacity.

[0063] In summary, this application proposes an organic adsorption detection method based on MOF material-MIL-101 (Cr). By testing the adsorption capacity of MOF material for VOC substances, the high specific surface area and porosity of MOF material are used to effectively enrich low-concentration VOCs in human exhaled breath, making up for the deficiency of direct detection due to low concentration and difficulty in obtaining accurate data. The MOF-based VOC enrichment test method is particularly suitable for the detection of exhaled VOCs in the concentration range of ppt to ppb, adapting to the capture needs of trace components in human exhaled breath and increasing the detection sensitivity. It has important application value for health monitoring and disease screening, and can provide a reliable detection method for early diagnosis.

[0064] Embodiment 2 Furthermore, in order to explore which VOCs substances the MOF material in the specific implementation mode one has an adsorption effect on and can provide an enrichment effect in the process of detecting VOCs in human exhaled breath, this embodiment also provides the detection results of some specific VOCs substance standards, and the specific standards include: acetone, indole, p-cresol, propionic acid, octanal, butyraldehyde, heptanal, butyric acid, phenol, 2-phenylethylamine, malic acid and DMSO.

[0065] The above substances are all currently detectable exhaled VOCs. When using GC-MS and / or LC-MS to analyze exhaled breath, carbonyl compounds such as butyraldehyde and octanal cannot be directly detected without an enrichment process before analysis due to their low concentration (ppb level). Based on the method in Example 1, these VOCs can be enriched in MOF and detected after desorption.

[0066] In this embodiment, the parameters of the GC-MS equipment are as follows: Instrument model: 7890B-5977B; Inlet parameters: temperature: 250℃; pressure: 9.8 psi; purge flow: 3mL / min, split ratio 0-20:1. Chromatographic column parameters: The specific chromatographic column model is: HP-5MS; flow: 0.8 mL / min; Inlet parameters: temperature: 250℃; pressure: 9.8 psi; purge flow: 3 mL / min, split ratio 0-20:1; MS equipment parameters: ion source type: EI; scan type: full scan; scan range: 40-450 Da; scan speed: 1562 u / s; scan frequency: 3.6Da / s; cycle time: 285.04 ms.

[0067] The column temperature parameters are shown in the following table:

[0068] The above table shows that the initial parameters of the chromatographic column are: the column temperature is 35°C, maintained for 2 minutes; then the temperature is increased to 150°C at a rate of 8°C / min and maintained at 150°C for 1 minute; then the temperature is increased to 250°C at a rate of 50°C / min and maintained at 250°C for 2 minutes. The total running time is 21.375 minutes.

[0069] The specific test results include the test method described in the above-mentioned specific embodiment 1, which includes four test processes for each substance, including: ① a blank control group containing neither MOF nor VOC, ② a control group containing neither MOF nor VOC, ③ a control group containing neither VOC nor MOF, and ④ an experimental group containing both MOF and VOC.

[0070] like Figure 2-Figure 9 From the test results, it can be seen that MIL-101 (Cr) is heated after adsorption, and the adsorbed substances can be detected by SPME-GC-MS: acetone, propionic acid, octanal, butyraldehyde, heptanal, butyric acid, phenol, and DMSO (dimethyl sulfoxide).

[0071] like Figure 10-13 From the test results, it can be seen that MIL-101 (Cr) was heated after adsorption, and no adsorbed substances were detected by SPME-GC-MS: indole, p-cresol, 2-phenylethylamine, and malic acid.

[0072] Based on the above test results, it can be seen that MIL-101(Cr) can detect acetone, propionic acid, octanal, butyraldehyde, heptanal, butyric acid, phenol and DMSO after heating desorption, indicating that MIL-101(Cr) has a strong adsorption capacity for these VOCs. This experimental result helps to verify the effectiveness of MIL-101(Cr) in selectively adsorbing certain VOCs, and provides a reference for further research on the application of MOF in the analysis of exhaled VOCs. At the same time, the above test results also revealed that MIL-101(Cr) cannot effectively adsorb VOCs such as indole, p-cresol, 2-phenylethylamine and malic acid, indicating that MOF materials have selective adsorption characteristics for different VOCs. This selectivity determines the types of VOCs that MIL-101(Cr) is suitable for enrichment, helping researchers to select suitable MOF materials or further adjust the material properties to expand its adsorption range.

[0073] In summary, the test results of MOF materials show that MIL-101(Cr) has a significant adsorption effect on common VOCs in human breath, such as acetone, propionic acid, and butyric acid, providing support for disease diagnosis or health monitoring in actual breath analysis.

[0074] The above are only preferred embodiments of the present invention. The protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for detecting organic matter adsorption based on MOF, characterized in that: include: S1: Activate the obtained MOF material; S2: filling the activated MOF material into a Teflon tube to prepare an adsorption tube containing the MOF material; S3: connecting the adsorption tube to the rear end of the ventilation pipeline containing the standard along the internal gas flow direction; S4: Input N2 to purge the ventilation pipeline, and purge the standard into the adsorption tube; S5: Desorbing the adsorbed MOF material to generate a gaseous sample, extracting the gaseous sample with an SPME probe, and performing GC-MS detection on the extracted SPME probe to obtain detection data.

2. The method for detecting organic matter adsorption based on MOF according to claim 1, characterized in that: The MOF material is specifically MIL-101 (Cr); The activation of the obtained MOF material specifically includes: The obtained MIL-101(Cr) was placed in vacuum activation at 150°C for 12 h; The step of filling the activated MOF material into the Teflon tube specifically includes: filling 100 mg of the activated MOF material into the Teflon tube to prepare an adsorption tube; After filling the activated MOF material into the Teflon tube, the method further comprises: Glass wool is filled at both ends of the Teflon tube.

3. The method for detecting organic matter adsorption based on MOF according to claim 1, characterized in that: The inputting of N2 to purge the ventilation pipeline to purge the standard product into the adsorption tube specifically includes: N2 was input at a flow rate of 0.5 L / min to purge the ventilation line, and the standard substance was purged into the adsorption tube until the standard substance in the ventilation line was completely volatilized.

4. The method for detecting organic matter adsorption based on MOF according to claim 1, characterized in that: The standard substance is specifically one or more of the following substances: Acetone, indole, p-cresol, propionic acid, octanal, butyraldehyde, heptaldehyde, butyric acid, phenol, 2-phenylethylamine, malic acid and DMSO.

5. The method for detecting organic matter adsorption based on MOF according to claim 1, characterized in that: Desorbing the adsorbed MOF material to generate a gaseous sample specifically includes: The adsorbed MOF material was transferred to a headspace bottle and heated in an oil bath at 150° for 10 min to generate a gaseous sample.

6. The method for detecting organic matter adsorption based on MOF according to claim 5, characterized in that: The gaseous sample is extracted by using an SPME probe, and the extracted SPME probe is subjected to GC-MS detection to obtain detection data, specifically including: Inserting the SPME probe into the headspace bottle to extract the gaseous sample in the headspace bottle for 5 minutes, and performing GC-MS detection on the extracted SPME probe to obtain detection data; The material of the SPME probe is specifically: quartz fiber and / or StableFlex fiber; The quartz fiber is coated with a Polyacrylate coating; The StableFlex fiber is coated with one or more of a PDMS coating, a DVB coating, and a CAR coating.

7. The method for detecting organic matter adsorption based on MOF according to claim 1, characterized in that: The step of performing GC-MS detection on the extracted SPME probe to obtain detection data specifically includes: inserting the extracted SPME probe into a chromatographic device to perform chromatographic separation on the VOCs extracted by the SPME probe; The VOCs separated by the chromatography are input into the mass spectrometer one by one to obtain the detection data.

8. The method for detecting organic matter adsorption based on MOF according to claim 7, characterized in that: The parameters of the chromatographic equipment are specifically: The specific chromatographic column model is: HP-5MS; The temperature of the chromatographic column is specifically controlled by the following steps: the column temperature is 35°C for 2 minutes; then the temperature is raised to 150°C at a rate of 8°C / min and maintained at 150°C for 1 minute; then the temperature is raised to 250°C at a rate of 50°C / min and maintained at 250°C for 2 minutes. The total operating time is 21.375 minutes. Flow rate: 0.8 mL / min; Inlet parameters: Temperature: 250 °C; Pressure: 9.8 psi; Purge flow: 3 mL / min, split ratio 0-20:

1.

9. The method for detecting organic matter adsorption based on MOF according to claim 7, characterized in that: The parameters of the mass spectrometer are specifically: Ion source type: EI; Scan type: full scan; Scan range: 40-450 Da; Scan speed: 1562 u / s; Scanning frequency: 3.6 Da / s; Cycle time: 285.04 ms.

10. The method for detecting organic matter adsorption based on MOF according to claim 1, characterized in that: Before step S1, the method further includes: Use N2 to purge the standard product to form a standard gas sample; directly use an SPME probe to extract the standard gas sample at the outlet of the ventilation pipeline for 1-2 minutes; wherein no adsorption tube is provided on the ventilation pipeline; The extracted SPME probe is subjected to GC-MS detection to generate standard test results; Based on the standard detection result, it is determined whether the standard product can be purged by N2 to form VOCs gas. If so, step S1 is executed.

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