Long-chain alkane online analysis method and system based on comprehensive two-dimensional gas chromatography and aerosol thermal desorption analyzer

Abstract

The invention belongs to the field of long-chain alkane online analysis systems, and discloses a long-chain alkane online analysis method and system based on comprehensive two-dimensional gas chromatography and an aerosol thermal desorption analyzer. The method comprises the following steps: during sampling, sucking ambient air through a cyclone separator with a PM2.5 cutting head, then removing gas-phase organic matters through a multi-channel carbon remover, and then intensively collecting particulate matters to a thermal desorption unit (CTD); the analyte after thermal desorption is re-concentrated into a focusing trap (FT) at 45 DEG C; starting separation and analysis of GC * GC-MS (gas chromatography-mass spectrometry); and the separated compound enters a mass spectrometer for mass spectrometry. According to the method, the total time from pollutant collection to analysis is controlled within two hours, and the change characteristics of long-chain alkane in the generation and elimination process of a pollution event can be effectively captured.

Description

Technical Field

[0001] The invention belongs to the field of long-chain alkane online analysis systems, and in particular relates to a long-chain alkane online analysis method and system based on comprehensive two-dimensional gas chromatography and aerosol thermal desorption analyzer. Background Art

[0002] Organic aerosol (OA) is a type of atmospheric fine particulate matter (PM 2.5 ) is an important component of the lower troposphere, accounting for about 20% to 60% of the atmospheric particulate matter. In recent decades, researchers have conducted a large number of field observations, laboratory analyses and simulations on organic aerosols. Among them, long-chain alkanes (with carbon numbers greater than 12) as an important component of OA can not only indicate the source and composition of aerosols, but also affect PM 2.5 Physical and chemical properties, and therefore have important environmental and climate significance. The emission of long-chain alkanes is closely related to activities such as combustion sources, industrial emissions, and biomass burning, so their concentration and distribution can be used as important indicators for assessing air quality and pollution sources. In addition, the accumulation of long-chain alkanes in aerosols may affect cloud formation and precipitation processes, thereby indirectly affecting climate change. Therefore, studying the behavior of long-chain alkanes in the atmosphere is crucial to understanding atmospheric chemistry and climate systems. However, the current measurement of long-chain alkanes in OA faces multiple challenges. For example, aerosol samples are complex and contain a variety of interfering substances, which makes separation and quantitative analysis difficult; the concentration of long-chain alkanes is usually low, and the instrument detection limit is high; the measurement results of long-chain alkanes need to be combined with other chemical components for comprehensive analysis, which increases the complexity of data interpretation, etc.

[0003] At present, quartz filter sampling combined with gas chromatography-mass spectrometry (GC-MS) offline analysis is the most commonly used method for detecting long-chain alkanes, but it has some significant disadvantages. For example, filter sampling usually takes a long time (from several hours to several days) to ensure that enough sample volume is captured. This long sampling cannot capture short-term changes in pollutant concentrations, limiting the capture of instantaneous pollution events; secondly, during the long sampling process, particulate long-chain alkanes may be transferred to the gas phase through gas-particle distribution and lost, resulting in an underestimation of the measured concentration. This loss is particularly evident under high temperature or high wind speed conditions. The online aerosol thermal desorption analyzer (TAG) developed in recent years can collect PM2.5 concentrations at hourly resolution. 2.5, enabling it to capture the dynamic changes of emission sources and air masses, and can effectively reduce the errors caused by long-term sampling. However, for complex samples (such as environmental aerosols or biological samples), the GC-MS that comes with the TAG system may not be able to effectively separate all components, especially when there are multiple compounds with similar structures in the sample, which is prone to co-elution problems, resulting in "bulges" on the chromatogram, where the substances contained in the "bulges" are called unresolved complex mixtures (UCM). In order to improve the separation efficiency of compounds in complex samples, two-dimensional gas chromatography (GC×GC) has been introduced into offline detection for analysis. After preliminary separation in the first-dimensional chromatographic column, the separated components are quickly transferred to the second-dimensional chromatographic column for further separation. This double separation method can effectively improve the separation efficiency of the analyte. However, offline two-dimensional gas chromatography cannot capture the generation and elimination process of pollution events, and each sample needs to be processed and analyzed separately, further prolonging the analysis cycle. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides an online analysis method and system for long-chain alkanes based on comprehensive two-dimensional gas chromatography and aerosol thermal desorption analyzer.

[0005] The present invention is achieved by an online analysis method for long-chain alkanes based on comprehensive two-dimensional gas chromatography and aerosol thermal desorption analyzer, the method comprising:

[0006] S1: When sampling, through the PM 2.5 The cyclone separator of the cutting head inhales ambient air, which is then passed through a multi-channel carbon remover to remove gas phase organic matter, and then the particulate matter is collected in a thermal desorption unit (CTD) with a sampling time of 60 minutes;

[0007] S2: Subsequently, the captured organic matter is vaporized through the temperature program process of CTD, and then introduced into the subsequent focused trap (FT); before thermal desorption, 5 μL of internal standard mixed solution is added to the CTD unit;

[0008] S3: Then, the FT was heated to 315°C and backflushed with 7 ml / min of helium. The analyte was introduced into the one-dimensional GC column through a valveless injection system. This process took 12 minutes.

[0009] S4: Then the GC×GC-MS starts the separation and analysis sequence; wherein the GC×GC temperature program is: first keep at 45°C for 5 minutes, then heat to 195°C at a rate of 6°C / min and keep at this temperature for 2 minutes, then heat to 300°C at a rate of 7°C / min and keep at this temperature for 12 minutes; the analysis time for each sample is 60 minutes, and at the same time, the TAG system collects the next environmental sample while the GC×GC-MS system is running, and repeats this process;

[0010] S5: The separated compounds enter the mass spectrometer and first undergo electron bombardment EI in the ion source. During this process, the sample molecules are bombarded by high-energy electrons, causing the molecules to break and the compounds to be ionized to form charged ions. The generated ions are accelerated and focused and enter the quadrupole mass spectrometer. The accelerating electric field enables the ions to gain kinetic energy and form a high-energy ion beam. The ions are separated in the mass spectrometer according to their mass-to-charge ratio (m / z). Ions with different mass-to-charge ratios move in different ways in the analyzer, thereby achieving separation. The separated ions are captured by the detector to generate a mass spectrum, which shows the relationship between the relative abundance of the ions and the mass-to-charge ratio. By comparing with the NIST library, the compounds in the sample can be identified and qualitative and quantitative analysis can be performed.

[0011] The temperature program of the CTD was as follows: the initial temperature was set at 45°C for 2 minutes, then increased to 330°C at a rate of 50°C per minute, and maintained at 330°C for 12 minutes, and the sample was desorbed from the CTD.

[0012] The internal standard mixed solution is deuterated alkane.

[0013] The one-dimensional GC chromatographic column is DB-5MS, with specifications of 30m×0.25mm×0.25μm;

[0014] The operating mode of two-dimensional GC is to connect the second-dimensional GC column through a solid-state thermal modulator on the basis of the original one-dimensional GC column, and finally analyze it through a detector; in this operating mode, the flow rate of the first-dimensional column is the same as the flow rate of the second-dimensional column.

[0015] The solid-state thermal modulator is mainly composed of a cold zone in the middle and two hot zones on both sides, which are respectively called the left inlet hot zone and the right outlet hot zone; inside the cold zone, a metal block is close to the semiconductor refrigeration element to achieve cooling; the two hot zones are heated by heating plates; a copper needle is installed between the two hot zones and the cold zone, one end of which is locked on the wall of the hot zone to effectively conduct the temperature of the hot zone to the entire length of the copper needle; the other end extends into the cold zone and keeps a certain distance from the metal block in the cold zone without contacting; such a design not only ensures extremely fast temperature switching, but also limits the thermal crosstalk between the cold zone and the hot zone, realizing three temperature zones Independent control; the copper needles in the two hot zones and the central hole of the metal block running through the cold zone are precisely aligned to ensure that a fused silica capillary modulation column passes smoothly; there is a rotating solenoid valve behind the right hot zone, and its extended shaft extends into the hot zone to connect to a metal swing arm; the modulation column is fixed to the end gripper of the metal swing arm, so as to convert the arc rotation of the solenoid valve into horizontal movement of the modulation column in the three temperature intervals; the modulation column is bent into a column ring in each of the two hot zones, and extends into the column temperature box through the copper tube transmission line fixed at the bottom of the hot zone, and is connected to the inlet end of the one-dimensional column and the outlet end of the two-dimensional column.

[0016] The modulation process of the solid-state thermal modulator is achieved by moving the modulation column back and forth between different temperature zones; when the modulation column moves to the left, a certain section thereof moves from the cold zone to the inlet hot zone, and the compounds previously condensed or retained in the cold zone are reheated and released; at the same time, another section moves from the outlet hot zone to the cold zone, so that the compounds released from the red part of the first stage are recondensed or retained in the black part of the second stage; after a period of time, when the modulation column moves to the right, the first stage re-enters the cold zone, cold-condenses the compounds distilled from the first-dimensional column, and prevents them from entering the two-dimensional column; the second stage moves to the outlet hot zone, and quickly releases the compounds previously cold-condensed in the second stage to the second-dimensional column for two-dimensional analysis; the modulation column continuously shuttles between the three temperature zones, forming a classic two-stage thermal modulation process.

[0017] The embodiment of the present invention provides an online analysis system for long-chain alkanes based on comprehensive two-dimensional gas chromatography and aerosol thermal desorption analyzer, and the system specifically includes:

[0018] TAG sampling module: When sampling, through the PM 2.5 The cyclone separator of the cutting head draws in ambient air, which is then passed through a multi-channel carbon remover to remove gaseous organic matter;

[0019] Thermal desorption analysis module: connected to the standard sample injection system, the particulate matter is collected in the thermal desorption unit CTD, the sampling time is 60 minutes, and then the captured organic matter is vaporized through the programmed temperature rise process of CTD, and then introduced into the subsequent FT; the analytes after thermal desorption are re-concentrated into the FT at 45°C; before thermal desorption, 5μL of the internal standard mixed solution is added to the CTD unit; then, the FT is heated to 315°C, and back-flushed with 7ml / min of helium, and the analytes are introduced into the one-dimensional GC column through the valveless injection system, which takes 12 minutes;

[0020] Mass spectrometry module: connected to the thermal desorption analysis system, the separated compounds enter the mass spectrometer and first pass through the ion source electron bombardment EI. During this process, the sample molecules are bombarded by high-energy electrons, causing the molecules to break, and the compounds are ionized to form charged ions; the generated ions are accelerated and focused and enter the quadrupole mass spectrometer; the accelerating electric field enables the ions to gain kinetic energy and form a high-energy ion beam; the ions are separated in the mass spectrometer according to their mass-to-charge ratio (m / z), and ions with different mass-to-charge ratios move in different ways in the analyzer, thereby achieving separation; the separated ions are captured by the detector to generate a mass spectrum, showing the relationship between the relative abundance of the ions and the mass-to-charge ratio; by comparing with the NIST library, the compounds in the sample can be identified and qualitative and quantitative analysis can be performed.

[0021] An embodiment of the present invention provides a computer device, which includes a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the online analysis method for long-chain alkanes based on comprehensive two-dimensional gas chromatography and aerosol thermal desorption analyzer.

[0022] An embodiment of the present invention provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the processor executes the steps of the online analysis method for long-chain alkanes based on comprehensive two-dimensional gas chromatography and aerosol thermal desorption analyzer.

[0023] An embodiment of the present invention provides an information data processing terminal, which is used to implement the long-chain alkane online analysis system based on comprehensive two-dimensional gas chromatography and aerosol thermal desorption analyzer.

[0024] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0025] First, for the analysis of long-chain alkanes, most of the related technologies use filter membrane sampling and experimental analysis, which has low time resolution. In addition, a small number of studies use two-dimensional gas chromatography technology for offline analysis of samples, which cannot avoid complex pre-treatment processes. This technology combines TAG with GC×GC to overcome the above problems. The resulting TAG-GC×GC system has the following advantages:

[0026] The front end of the present invention adopts TAG for air sampling, and TAG can be used to achieve rapid capture of long-chain alkanes within 30 minutes, which greatly reduces the loss of samples during long-term sampling. The back-end separation and analysis device of the present invention uses GC×GC-MS, which can significantly improve the separation efficiency compared with traditional analysis methods, especially when dealing with complex samples, it can effectively separate compounds with similar structures, further improve the sensitivity and selectivity of the analysis, reduce the interference of co-eluting compounds, and the arrangement of compounds on the chromatogram is more regular; in addition, the total time from pollutant collection to the end of analysis of the present invention is controlled within two hours, which can effectively capture the change characteristics of long-chain alkanes in the process of pollution event generation and elimination. In addition, the hour-level data resolution is of great reference significance for subsequent indication of pollution characteristics and determination of emission sources; in addition, the present technology automatically imports GC×GC-MS for in-situ analysis after TAG automatic sampling to obtain the response signal of long-chain alkanes, which reduces the loss and pollution of samples during storage, pretreatment and transfer; at the same time, the present invention saves a series of processes such as sample collection, transportation, pretreatment, etc. through automated analysis, and reduces the manpower and material costs required for sample storage, transportation and pretreatment.

[0027] Second, the expected benefits and commercial value of the technical solution of the present invention after transformation are as follows: This technical solution has great industrialization potential, especially in the field of atmospheric environment monitoring. It is expected that after the TAG-GC×GC system enters the market, it will gradually replace traditional offline detection equipment and significantly improve detection efficiency and data quality. From the market level, this technology has a wide range of potential users and has good market expectations.

[0028] Third, the technical solution of the present invention solves a technical problem that people have been eager to solve but have never succeeded in solving: this technology realizes the combination of online capture of long-chain alkanes and two-dimensional gas chromatography column analysis, and realizes the acquisition of hourly data, solving the problems of long offline sampling and analysis time and high human resource requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a flow chart of an online analysis system for long-chain alkanes based on comprehensive two-dimensional gas chromatography and aerosol thermal desorption analyzer provided by an embodiment of the present invention;

[0030] Figure 2is a schematic diagram of a TAG-GC×GC system provided by an embodiment of the present invention;

[0031] Figure 3 This is the GC×GC operation mode provided by the embodiment of the present invention;

[0032] Figure 4 is a structural diagram of a solid-state thermal modulator provided by an embodiment of the present invention;

[0033] Figure 5 The solid-state thermal modulator modulation process provided by the embodiment of the present invention;

[0034] Figure 6 It is established by the TAG method provided by the embodiment of the present invention;

[0035] Figure 7 It is a TAG work log provided by an embodiment of the present invention;

[0036] Figure 8 is a two-dimensional spectrum of long-chain alkanes provided by an embodiment of the present invention;

[0037] Fig. 9 is an extracted mass spectrum provided by an embodiment of the present invention;

[0038] Fig.10 It is the peak result detailed information provided by the embodiment of the present invention;

[0039] Fig.11 is a front view of TAG-GC×GC provided by an embodiment of the present invention;

[0040] Fig.12 It is a full two-dimensional solid-state thermal modulator provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0042] Example: Online detection of long-chain alkanes in ambient air using comprehensive two-dimensional gas chromatography (GC×GC) and aerosol thermal desorption analyzer (TAG)

[0043] Step S1: Sampling and particle collection

[0044] 1. Collect ambient air samples through a cyclone separator with a PM2.5 cutting head so that only PM2.5 particles enter the analysis system.

[0045] 2. Organic matter in the gas phase is removed by a multi-channel carbon stripper, ensuring that only samples containing particulate matter are collected in the thermal desorption unit (CTD).

[0046] 3. The sampling time is set to 60 minutes to ensure sufficient sample volume.

[0047] Step S2: Thermal desorption and focusing

[0048] 1. Before starting thermal desorption, add 5 μL of internal standard mixed solution containing deuterated alkanes to the CTD unit for subsequent quantitative analysis.

[0049] 2. Start the temperature rise program of CTD, set the initial temperature to 45°C and keep it for 2 minutes, then increase the temperature to 330°C at a rate of 50°C / min and keep it at 330°C for 12 minutes. During this process, the organic matter in the particles is vaporized and captured in the focusing trap (FT).

[0050] Step S3: Sample injection

[0051] 1. The focusing trap (FT) was heated to 315°C, backflushed with helium at 7 ml / min, and the sample was introduced into the one-dimensional chromatographic column (GC column) through a valveless injection system.

[0052] 2. The one-dimensional GC column used was DB-5MS (specification: 30 m × 0.25 mm × 0.25 μm), and the injection time was approximately 12 min.

[0053] Step S4: GC×GC separation

[0054] 1. Start the GC×GC-MS system and separate the samples according to the following temperature program:

[0055] The initial temperature was 45°C and maintained for 5 minutes;

[0056] Raise the temperature to 195°C at a rate of 6°C / min and hold for 2 min;

[0057] The temperature was then raised to 300°C at a rate of 7°C / min and maintained at this temperature for 12 minutes.

[0058] 2. The analysis time for each sample is 60 minutes. The TAG system collects the next environmental sample while the GC×GC-MS is running, achieving cyclic sampling.

[0059] Step S5: Mass spectrometry detection and data analysis

[0060] 1. The separated compounds enter the mass spectrometer and are ionized by the electron bombardment ion source (EI). The sample molecules are bombarded by high-energy electrons and broken into charged ions.

[0061] 2. The generated ions are accelerated and focused and then enter the quadrupole mass spectrometer, where they are separated according to their mass-to-charge ratio (m / z) and captured by the detector.

[0062] 3. By comparing with the standard spectra in the NIST database, the qualitative and quantitative analysis of the compounds in the sample can be achieved, and the concentration distribution of long-chain alkanes in the air sample can be obtained.

[0063] The mass spectrometry data obtained from the analysis can evaluate the alkane pollution level of PM2.5 in air quality based on the concentration of long-chain alkanes in different regions, and provide data support for source analysis of atmospheric pollutants and environmental monitoring.

[0064] like Figure 1 As shown, an embodiment of the present invention provides an online analysis method for long-chain alkanes based on comprehensive two-dimensional gas chromatography and aerosol thermal desorption analyzer, the method comprising:

[0065] S1: When sampling, through the PM 2.5 The cyclone separator of the cutting head inhales ambient air, which is then passed through a multi-channel carbon remover to remove gas phase organic matter, and then the particulate matter is collected in a thermal desorption unit (CTD) with a sampling time of 60 minutes;

[0066] S2: Subsequently, the captured organic matter is vaporized through the temperature program process of CTD, and then introduced into the subsequent focused trap (FT); before thermal desorption, 5 μL of internal standard mixed solution is added to the CTD unit;

[0067] S3: Then, the FT was heated to 315°C and backflushed with 7 ml / min of helium. The analyte was introduced into the one-dimensional GC column through a valveless injection system. This process took 12 minutes.

[0068] S4: Then the GC×GC-MS starts the separation and analysis sequence; wherein the GC×GC temperature program is: first keep at 45°C for 5 minutes, then heat to 195°C at a rate of 6°C / min and keep at this temperature for 2 minutes, then heat to 300°C at a rate of 7°C / min and keep at this temperature for 12 minutes; the analysis time for each sample is 60 minutes, and at the same time, the TAG system collects the next environmental sample while the GC×GC-MS system is running, and repeats this process;

[0069] S5: The separated compounds enter the mass spectrometer and first undergo electron bombardment EI in the ion source. During this process, the sample molecules are bombarded by high-energy electrons, causing the molecules to break and the compounds to be ionized to form charged ions. The generated ions are accelerated and focused and enter the quadrupole mass spectrometer. The accelerating electric field enables the ions to gain kinetic energy and form a high-energy ion beam. The ions are separated in the mass spectrometer according to their mass-to-charge ratio (m / z). Ions with different mass-to-charge ratios move in different ways in the analyzer, thereby achieving separation. The separated ions are captured by the detector to generate a mass spectrum, which shows the relationship between the relative abundance of the ions and the mass-to-charge ratio. By comparing with the NIST library, the compounds in the sample can be identified and qualitative and quantitative analysis can be performed.

[0070] The temperature program of the CTD was as follows: the initial temperature was set at 45°C for 2 minutes, then increased to 330°C at a rate of 50°C per minute, and maintained at 330°C for 12 minutes, and the sample was desorbed from the CTD.

[0071] The internal standard mixed solution is deuterated alkane.

[0072] The one-dimensional GC chromatographic column is DB-5MS, with specifications of 30m×0.25mm×0.25μm;

[0073] like Figure 3 As shown, the operation mode of the two-dimensional GC is to connect the second-dimensional GC column through a solid-state thermal modulator on the basis of the original one-dimensional GC column, and finally analyze it through a detector; in this operation mode, the flow rate of the first-dimensional column is the same as the flow rate of the second-dimensional column.

[0074] like Figure 4 As shown in the figure, the solid-state thermal modulator is mainly composed of a cold zone in the middle and two hot zones on both sides, which are respectively called the left inlet hot zone and the right outlet hot zone; inside the cold zone, a metal block is close to the semiconductor refrigeration element to achieve cooling; the two hot zones are heated by heating plates; a copper needle is installed between the two hot zones and the cold zone, one end of which is locked on the wall of the hot zone to effectively conduct the temperature of the hot zone to the entire length of the copper needle; the other end extends into the cold zone and keeps a certain distance from the metal block in the cold zone without contacting; this design not only ensures extremely fast temperature switching, but also limits the thermal crosstalk between the cold zone and the hot zone, realizing three-temperature The three zones are controlled independently; the copper needles in the two hot zones and the central hole of the metal block in the cold zone are precisely aligned to ensure that a fused silica capillary modulation column can pass through smoothly; there is a rotating electromagnetic valve behind the right hot zone, and its extended shaft extends into the hot zone to connect with a metal swing arm; the modulation column is fixed to the end gripper of the metal swing arm, so as to convert the arc rotation of the electromagnetic valve into horizontal movement of the modulation column in the three temperature zones; the modulation column is bent into a column ring in each of the two hot zones, and extends into the column temperature box through the copper tube transmission line fixed at the bottom of the hot zone, and is connected with the inlet end of the one-dimensional column and the outlet end of the two-dimensional column.

[0075] like Figure 5 As shown, the modulation process of the solid-state thermal modulator is achieved by moving the modulation column back and forth between different temperature zones; when the modulation column moves to the left, a certain section thereof moves from the cold zone to the inlet hot zone, and the compounds previously condensed or retained in the cold zone are reheated and released; at the same time, another section moves from the outlet hot zone to the cold zone, so that the compounds released from the red part of the first stage are recondensed or retained in the black part of the second stage; after a period of time, when the modulation column moves to the right, the first stage re-enters the cold zone, and the compounds distilled from the first-dimensional column are cold-condensed to prevent them from entering the two-dimensional column; the second stage moves to the outlet hot zone, and the compounds previously cold-condensed in the second stage are quickly released to the second-dimensional column for two-dimensional analysis; the modulation column continuously shuttles between the three temperature zones, forming a classic two-stage thermal modulation process.

[0076] The embodiment of the present invention provides an online analysis method of long-chain alkanes based on comprehensive two-dimensional gas chromatography and aerosol thermal desorption analyzer, and an online analysis system of long-chain alkanes based on comprehensive two-dimensional gas chromatography and aerosol thermal desorption analyzer, the system comprising:

[0077] TAG sampling module: When sampling, through the PM 2.5 The cyclone separator of the cutting head draws in ambient air, which is then passed through a multi-channel carbon remover to remove gaseous organic matter;

[0078] Thermal desorption analysis module: connected to the standard sample injection system, the particulate matter is collected in the thermal desorption unit CTD, the sampling time is 60 minutes, and then the captured organic matter is vaporized through the programmed temperature rise process of CTD, and then introduced into the subsequent FT; the analytes after thermal desorption are re-concentrated into the FT at 45°C; before thermal desorption, 5μL of the internal standard mixed solution is added to the CTD unit; then, the FT is heated to 315°C, and back-flushed with 7ml / min of helium, and the analytes are introduced into the one-dimensional GC column through the valveless injection system, which takes 12 minutes;

[0079] Mass spectrometry module: connected to the thermal desorption analysis system, the separated compounds enter the mass spectrometer and first pass through the ion source electron bombardment EI. During this process, the sample molecules are bombarded by high-energy electrons, causing the molecules to break, and the compounds are ionized to form charged ions; the generated ions are accelerated and focused and enter the quadrupole mass spectrometer; the accelerating electric field enables the ions to gain kinetic energy and form a high-energy ion beam; the ions are separated in the mass spectrometer according to their mass-to-charge ratio (m / z), and ions with different mass-to-charge ratios move in different ways in the analyzer, thereby achieving separation; the separated ions are captured by the detector to generate a mass spectrum, showing the relationship between the relative abundance of the ions and the mass-to-charge ratio; by comparing with the NIST library, the compounds in the sample can be identified and qualitative and quantitative analysis can be performed.

[0080] An embodiment of the present invention provides a computer device, which includes a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the online analysis method for long-chain alkanes based on comprehensive two-dimensional gas chromatography and aerosol thermal desorption analyzer.

[0081] An embodiment of the present invention provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the processor executes the steps of the online analysis method for long-chain alkanes based on comprehensive two-dimensional gas chromatography and aerosol thermal desorption analyzer.

[0082] An embodiment of the present invention provides an information data processing terminal, which is used to implement the long-chain alkane online analysis system based on comprehensive two-dimensional gas chromatography and aerosol thermal desorption analyzer.

[0083] Taking the running of a standard sample as an example, this paper introduces in detail how to use this technology to conduct qualitative and quantitative analysis of long-chain alkanes.

[0084] First, set up the method on the TAG system operating software. The standard sample system automatically applies external standards, solvents and internal standards. The sample is desorbed from the CTD and transferred to the one-dimensional GC column using a two-step thermal desorption method. Then, the sample is analyzed by GC×GC through a two-dimensional column connected to the modulator. The specific method settings are as follows: Figure 6 shown.

[0085] After the method is set up, the next step is to create a sequence. After uploading the sequence to the TAG system, save the work log, such as Figure 7 As shown. In the work log, the temperature changes of the heating part and the flow information of each part during the sequence operation will be recorded. After the instrument is running, the real-time sequence operation status of the instrument can also be queried in the status information of the software, which provides convenience for subsequent troubleshooting of instrument problems.

[0086] After the entire sequence run is completed, the two-dimensional chromatogram analysis software (Canvas) is opened to first obtain the structured two-dimensional spectrum of long-chain alkanes, such as Figure 8 As shown in the figure, long-chain alkanes appear in order of volatility, showing strips on the spectrum, and the depth of color represents the concentration of the substance.

[0087] In Canvas, load the NIST mass spectrum library for qualitative analysis. First, use the peak detection function of the 2D software to automatically integrate. After turning on the peak selection switch, randomly select a peak on the 2D spectrum. The mass spectrum of the selected compound is displayed in the mass spectrum (blue), and the highest matching compound of the compound is also displayed on the spectrum (red). The detailed information of the compound is displayed in the matching compound information table below the spectrum. Fig. 9 It can be seen that this compound is mainly composed of ion fragments of m / z=57, 71, and 85, which are the signature ion peaks of alkanes. First, we determine it to be an alkane. In the matching compound information, the substance matched by the NIST library is C15H32, and the reverse matching degree is 841. Then, based on the elution time of alkanes, it is finally determined that this substance is C15H32, thus completing the qualitative identification of a substance.

[0088] Repeat the above method to find all the long-chain alkanes in the sample and perform qualitative analysis, and derive the peak areas of all long-chain alkanes for quantitative analysis. In the Canvas software, after performing peak integration, you can click on the peak result to view detailed information on all integrations, such as Fig.10 As shown in the figure, such as retention time, peak area and other information. By deriving the peak area of ​​the corresponding long-chain alkane, the internal standard method is used for quantification.

[0089] After importing the peak area into Excel, the quantitative part takes making a standard curve as an example. The C14-C40 long-chain alkane stock solution was diluted several times with n-hexane solution using a 10mL reagent bottle to prepare a working standard solution, and the final concentration of the long-chain alkane working solution was 0.32ng / μL. Table 1 shows the corresponding IS and other detailed information of the external standard (ES), and Table 2 lists the standard preparation details of the internal standard (IS). After injecting different volumes (ranging from 5 to 30μL) of working standard solution and a fixed volume (5μL) of IS into the CTD, the standard curve was constructed by fitting the normalized peak area of ​​ES to the corresponding IS. It can be seen from Table 1 that the R2 of the long-chain alkane standard curve is above 0.90 as a whole, indicating that it has a good linear response.

[0090] Table 1. ES sample names and their corresponding IS and standard curve R 2 and quantitative ions, etc.

[0091]

[0092]

[0093] Table 2. IS substance detailed information list

[0094]

[0095] Fig.11 It is a front view of TAG / GC×GC-MS, in which the part labeled 1 is the collection and thermal desorption unit (CTD) mentioned above, the part labeled 2 is the standard injection system, the part labeled 3 is the focusing trap, and the part labeled 4 is the full two-dimensional solid-state thermal modulator.

[0096] Fig.12 This is a detailed diagram of the components of the full two-dimensional solid-state thermal modulator. Label 1 is the heat insulation pad of the inlet hot zone, label 2 is the heat insulation board of the outlet hot zone, label 3 is the guide rod, label 4 is the gripper, label 5 is the modulation rod, label 6 is the millet grain, which is used to connect the modulation columns at both ends of the inlet hot zone and the outlet hot zone. Label 7 is the semiconductor refrigeration zone.

[0097] It should be noted that the embodiments of the present invention can be implemented by hardware, software, or a combination of software and hardware. The hardware part can be implemented using dedicated logic; the software part can be stored in a memory and executed by an appropriate instruction execution system, such as a microprocessor or dedicated design hardware. It can be understood by a person of ordinary skill in the art that the above-mentioned devices and methods can be implemented using computer executable instructions and / or contained in a processor control code, such as a carrier medium such as a disk, CD or DVD-ROM, a programmable memory such as a read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. Such code is provided on the carrier medium. The device and its modules of the present invention can be implemented by hardware circuits such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, etc., or programmable hardware devices such as field programmable gate arrays, programmable logic devices, etc., can also be implemented by software executed by various types of processors, and can also be implemented by a combination of the above-mentioned hardware circuits and software, such as firmware.

[0098] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with the technical field within the technical scope disclosed by the present invention and within the spirit and principle of the present invention should be covered by the protection scope of the present invention.

Claims

1. An online analysis method for long-chain alkanes based on comprehensive two-dimensional gas chromatography and aerosol thermal desorption analyzer, characterized in that: The method includes: S1: When sampling, through the PM 2.5 The cyclone separator of the cutting head inhales ambient air, which is then passed through a multi-channel carbon remover to remove gas phase organic matter, and then the particulate matter is collected in a thermal desorption unit (CTD) with a sampling time of 60 minutes; S2: Subsequently, the captured organic matter is vaporized through the temperature program process of CTD, and then introduced into the subsequent focusing trap; before thermal desorption, 5 μL of internal standard mixed solution is added to the CTD unit; S3: Then, the FT was heated to 315°C and backflushed with 7 ml / min of helium. The analyte was introduced into the one-dimensional GC column through a valveless injection system. This process took 12 minutes. S4: Then the GC×GC-MS starts the separation and analysis sequence; wherein the GC×GC temperature program is: first keep at 45°C for 5 minutes, then heat to 195°C at a rate of 6°C / min and keep at this temperature for 2 minutes, then heat to 300°C at a rate of 7°C / min and keep at this temperature for 12 minutes; the analysis time for each sample is 60 minutes, and at the same time, the TAG system collects the next environmental sample while the GC×GC-MS system is running, and repeats this process; S5: The separated compounds are ionized by electron bombardment in the mass spectrometer and then enter the quadrupole mass spectrometer. The ions are separated according to the mass-to-charge ratio to generate a mass spectrum, which is then compared with the NIST library for qualitative and quantitative analysis.

2. The long-chain alkane online analysis method according to claim 1, characterized in that: The temperature program of CTD was as follows: the initial temperature was set at 45 °C for 2 min, then increased to 330 °C at a rate of 50 °C / min and maintained at 330 °C for 12 min to allow the sample to desorb from CTD.

3. The long-chain alkane online analysis method according to claim 1, characterized in that: The internal standard mixed solution is deuterated alkane.

4. The long-chain alkane online analysis method according to claim 1, characterized in that: The one-dimensional GC chromatographic column is DB-5MS, with a specification of 30m×0.25mm×0.25μm; the two-dimensional GC operation mode is to connect the second-dimensional GC column through a solid-state thermal modulator on the basis of the one-dimensional GC column, and analyze through a detector.

5. The long-chain alkane online analysis method according to claim 4, characterized in that: The solid-state thermal modulator consists of a cold zone and two hot zones on the left and right. The cold zone is equipped with a metal block that is close to the semiconductor refrigeration element; the hot zones are heated by heating plates and each is equipped with a copper needle connected to the cold zone to achieve independent control of the three temperature zones and rapid temperature switching.

6. The long-chain alkane online analysis method according to claim 4, characterized in that: The modulation process of the solid-state thermal modulator is achieved by moving the modulation column between the cold zone and the hot zone. When the modulation column moves left and right, the compound alternates between condensation and release, forming a two-stage thermal modulation process.

7. The long-chain alkane online analysis method according to claim 6, characterized in that: The modulation column cools the polymerized substances in the cold zone and prevents them from entering the two-dimensional column, and releases the cool polymerized compounds in the outlet hot zone to enter the two-dimensional column for analysis, thereby achieving secondary separation and analysis.

8. An online analysis system for long-chain alkanes based on comprehensive two-dimensional gas chromatography and aerosol thermal desorption analyzer based on the online analysis method for long-chain alkanes based on comprehensive two-dimensional gas chromatography and aerosol thermal desorption analyzer as claimed in claims 1 to 7, characterized in that: The system includes: TAG sampling module: When sampling, through the PM 2.5 The cyclone separator of the cutting head draws in ambient air, which is then passed through a multi-channel carbon remover to remove gaseous organic matter; Thermal desorption analysis module: connected to the standard sample injection system, the particles are collected in the thermal desorption unit CTD, the sampling time is 60 minutes, and then the captured organic matter is vaporized through the programmed temperature rise process of CTD, and then introduced into the subsequent focusing trap FT; the analytes after thermal desorption are re-concentrated into the focusing trap at 45°C; before thermal desorption, 5μL of the internal standard mixed solution is added to the CTD unit; then, the FT is heated to 315°C, and back-flushed with 4ml / min of helium, and the analyte is introduced into the one-dimensional GC column through the valveless injection system, which takes 12 minutes; Mass spectrometry module: connected to the thermal desorption analysis system, the separated compounds enter the mass spectrometer and first pass through the ion source electron bombardment EI. During this process, the sample molecules are bombarded by high-energy electrons, causing the molecules to break, and the compounds are ionized to form charged ions; the generated ions are accelerated and focused and enter the quadrupole mass spectrometer; the accelerating electric field enables the ions to gain kinetic energy and form a high-energy ion beam; the ions are separated in the mass spectrometer according to their mass-to-charge ratio (m / z), and ions with different mass-to-charge ratios move in different ways in the analyzer, thereby achieving separation; the separated ions are captured by the detector to generate a mass spectrum, showing the relationship between the relative abundance of the ions and the mass-to-charge ratio; by comparing with the NIST library, the compounds in the sample can be identified and qualitative and quantitative analysis can be performed.

9. A computer-readable storage medium storing a computer program, wherein when the computer program is executed by a processor, the processor executes the steps of the online analysis method for long-chain alkanes based on comprehensive two-dimensional gas chromatography and aerosol thermal desorption analyzer as described in any one of claims 1 to 6.

10. An information data processing terminal, characterized in that: The information data processing terminal is used to implement the long-chain alkane online analysis system based on comprehensive two-dimensional gas chromatography and aerosol thermal desorption analyzer as described in claim 7.

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