Application of elemental carbon in laser desorption ionization mass spectrometry detection

Abstract

The invention relates to an application of elemental carbon in laser desorption ionization mass spectrometry detection, and the elemental carbon (EC) is obtained by cleaning and extracting components of organic carbon (OC) by using an incomplete combustion product Soot. The EC is used as a material of a graphite-like structure, is used as a substrate when environmental pollution particles are analyzed by using LDI-MS, and can enhance the detection strength of aromatic compounds in the particles. Furthermore, when the EC is used for analyzing aromatic substances, the EC has a better enhancement effect on substances containing reactive hydrogen (PAH with OC containing odd carbon in the invention, namely PAHodd) and substances with lower conjugacy. According to the device and the method, pollution particulate matters are recycled, detection and analysis of particulate matter components are facilitated, and the detection sensitivity of aromatic substances is improved.

Description

[0001] The present invention relates to the field of analysis and detection technology, and in particular to application of elemental carbon in enhancing the detection of polycyclic aromatic hydrocarbons by laser desorption ionization mass spectrometry. Background Art

[0002] Particulate matter refers to tiny solid or liquid particles suspended in the air, typically ranging in diameter from a few nanometers to tens of microns. These particles can originate from natural sources (such as dust and volcanic ash) or human activities (such as coal burning, traffic emissions, and industrial emissions). Particulate matter is ubiquitous in the atmosphere and has significant impacts on human health and environmental quality. The current global energy structure is still dominated by fossil fuels and biomass fuels, whose incomplete combustion produces black carbon (soot). Soot, a significant component of atmospheric particulate matter, can disrupt the global radiation balance and cloud condensation nuclei. It can also react with other pollutants in the environment, impacting the global climate and environment. Since the mid-1980s, scientists have been observing and studying soot. Surveys have shown that global soot emissions showed an annual upward trend from 1960 to 2007. The environmental impact and health risks of large-scale soot emissions cannot be ignored. Analyzing the concentration, composition, and sources of particulate matter can help assess air quality and formulate appropriate environmental policies and control measures. For example, by monitoring the concentration and composition of particulate matter, we can identify the primary pollutants and implement measures to reduce emissions. Particulate matter analysis can also help assess the effectiveness of control measures and monitor the progress of environmental improvements. Improving the sensitivity of detecting PAHs, the primary pollutant components in particulate matter, will further facilitate particulate matter analysis and control. Summary of the Invention

[0003] The present invention provides a use of elemental carbon (EC) in black carbon (Soot), a product of incomplete combustion in the environment, as a matrix material for laser desorption ionization mass spectrometry (LDI-MS).

[0004] According to an embodiment of the present invention, the LDI-MS is LDI FT-ICR MS positive ion mode detection.

[0005] According to an embodiment of the present invention, the elemental carbon (EC) is a carbon material having a graphite-like structure.

[0006] According to an embodiment of the present invention, the incomplete combustion product Soot is an incomplete combustion product of environmental pollution particulate matter, fossil fuels and biomass materials, such as C 1-12 Incomplete combustion products of alkanes, such as the incomplete combustion products of n-hexane.

[0007] According to an embodiment of the present invention, the matrix material includes a quartz plate and EC supported on the quartz plate.

[0008] According to an embodiment of the present invention, the matrix material has a specific enhancement effect on LDI-MS detection of substances containing active hydrogen.

[0009] According to an embodiment of the present invention, the substance containing active hydrogen is C 27-48 Organic substances, such as aromatic compounds, such as polycyclic aromatic hydrocarbons (PAH) and their derivatives. Preferably, the substance containing active hydrogen is a C 27-47 Organic compounds such as C 27-47 Aromatic compounds, such as C 27-47 Polycyclic aromatic hydrocarbons (PAH) and their derivatives, for example, one, two or more selected from the following compounds:

[0010]

[0011] According to an embodiment of the present invention, the EC is prepared by the following method:

[0012] The soot produced by incomplete combustion is washed with an organic solvent to remove the organic carbon (OC) in the soot to obtain EC.

[0013] According to an embodiment of the present invention, the organic solvent is selected from an alcohol solvent, a halogenated alkane solvent, a ketone solvent, an ester solvent, or an alkane solvent, for example, one, two, or more selected from methanol, ethanol, dichloromethane, chloroform, acetone, ethyl acetate, and n-hexane. For example, the organic solvent is selected from an alcohol solvent, a halogenated alkane solvent, and an alkane solvent. For example, dichloromethane, methanol, and n-hexane are used to clean the Soot.

[0014] In some embodiments, EC is prepared using the following method:

[0015] Step (1): adding liquid spectrally pure n-hexane into a premixed diffusion burner and burning to produce Soot;

[0016] Step (2): The Soot prepared in step (1) is extracted and washed with an organic solvent to obtain EC.

[0017] According to an embodiment of the present invention, the fuel delivery to the premixed diffusion burner in step (1) is achieved through a cotton wick extending into the liquid fuel storage.

[0018] According to an embodiment of the present invention, in step (1), the gas flow used for combustion is a mixture of high-purity O2 and N2, for example, a mixed gas with an O2 content of 21.3% by volume.

[0019] According to an embodiment of the present invention, in step (1), the volume ratio of fuel to oxygen is 1:(0.1-0.5), such as 1:0.18.

[0020] According to an embodiment of the present invention, in step (1), the Soot generated by the diffusion flame combustion is directly deposited on the quartz plate; further, the quartz plate is transferred to a bottle, the bottle is sealed, and stored in the dark for future use.

[0021] According to an embodiment of the present invention, a quartz plate is used when collecting Soot in step (1); preferably, a cleaned quartz plate is used.

[0022] According to an embodiment of the present invention, the quartz plate needs to be cleaned with ethanol and deionized water; preferably, the quartz plate is ultrasonically cleaned.

[0023] According to an embodiment of the present invention, the cleaned quartz plate is dried in an oven; preferably, the drying time is not less than 30 minutes.

[0024] According to an embodiment of the present invention, in step (1), when collecting the soot produced by combustion, the quartz plate needs to be placed above the flame; preferably, the quartz plate is 2 cm above the flame.

[0025] According to an embodiment of the present invention, in step (2), the quartz plate loaded with Soot is soaked and cleaned using three organic solvents of different polarities.

[0026] The organic solvents are chromatographically pure dichloromethane, methanol and n-hexane;

[0027] According to an embodiment of the present invention, in step (2), the three solvents are placed in a brown bottle during the extraction and cleaning process, and at least 15 ml of solvent is used for extraction and cleaning.

[0028] According to an embodiment of the present invention, in step (2), the extraction and cleaning process of dichloromethane, methanol and n-hexane is circulated for extraction and cleaning once, which constitutes one round, and the extraction process needs to be repeated for more than three rounds.

[0029] According to an embodiment of the present invention, in step (2), the extraction time of each reagent in the extraction and cleaning process is at least 15 minutes.

[0030] According to an embodiment of the present invention, in step (2), after the extraction and cleaning process, the step of drying the quartz plate loaded with EC is further included, and the drying time is 10-30 minutes, for example, 20 minutes;

[0031] After drying, the substance loaded on the quartz plate is EC.

[0032] According to an embodiment of the present invention, in step (2), after the extraction and cleaning process, the substance contained in the extract is organic carbon (OC), which is composed of aromatic substances.

[0033] According to an embodiment of the present invention, each ultrasonic cleaning time is not less than 15 minutes.

[0034] According to the embodiment of the present invention, one cycle of ethanol and deionized water cleaning is considered as one round, and the cleaning process needs to be repeated at least twice.

[0035] According to an embodiment of the present invention, the organic solution generated during the Soot cleaning process is subjected to rotary evaporation to obtain a concentrated solution containing OC.

[0036] Beneficial effects

[0037] The present invention utilizes the product of incomplete combustion, Soot, to obtain elemental carbon (EC) by washing and extracting the components of organic carbon (OC). EC, as a material with a graphite-like structure, can be used as a substrate when analyzing environmental pollution particulate matter using LDI-MS to enhance the detection intensity of aromatic compounds in particulate matter. Furthermore, when EC is used to analyze aromatic substances, it can detect substances containing active hydrogen (in this invention, OC contains PAH with an odd number of carbon atoms, i.e., PAH odd ), substances with lower conjugation have better enhancement effects. The present invention realizes the reuse of polluted particulate matter, facilitates the detection and analysis of particulate matter components, and improves the sensitivity of aromatic substance detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 Comparison of the spectra of OC@EC and EC prepared in Example 1 under the positive ion mode of laser desorption ionization Fourier transform particle cyclotron resonance mass spectrometry (LDI FT-ICR MS).

[0039] Figure 2 This is the LDI FT-ICR MS spectrum of OC in the positive ion mode in Comparative Example 1.

[0040] Figure 3 This is a comparison chart of the different enhancement effects of EC and graphite on PAH with different structures in Example 1.

[0041] Figure 4 This is the LDI FT-ICR MS spectrum in positive ion mode when the same content of OC is loaded on different contents of EC in Example 2. DETAILED DESCRIPTION

[0042] The technical solutions of the present invention will be described in further detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are encompassed within the scope of protection that the present invention is intended to protect.

[0043] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0044] Preparation Example 1

[0045] Liquid chromatography-grade n-hexane was added to a premixed diffusion burner and burned. A soot sample was collected for 20 seconds using a quartz plate starting from the 8th minute of flame combustion. During the collection process, the quartz plate was kept 2 cm above the flame and moved parallel to the smoke diffusion range to ensure sample uniformity.

[0046] The quartz plate was subjected to an extraction process (one round of extraction and cleaning with dichloromethane, methanol, and n-hexane was repeated three times. During the extraction and cleaning process, the three solvents were placed in a brown bottle, and at least 15 ml of solvent was used for extraction and cleaning. The extraction time for each reagent in the extraction and cleaning process was 15 minutes). After OC was extracted and separated, a quartz plate sample loaded with EC was obtained, which was recorded as quartz plate 1.

[0047] The main components of the obtained OC are polycyclic aromatic hydrocarbons (PAH) and their derivatives (Highly oxygenated organic molecules with high unsaturation formed upon photochemical aging of soot, Chem8, 2688–2699, October 13, 2022), which are further divided into PAHs with odd carbon numbers and PAHs with even carbon numbers (hereinafter referred to as PAH odd and PAH even Specifically, the structures of these polycyclic aromatic hydrocarbons (PAH) are shown in Table 1 below:

[0048] Table 1

[0049]

[0050] Preparation Example 2

[0051] The operation of Preparation Example 1 was repeated to obtain a quartz plate loaded with two portions of EC, which was designated as Quartz Plate 2.

[0052] Example 1

[0053] The OC concentrated solution produced after extraction and rotary evaporation in Preparation Example 1 was coated on the quartz plate loaded with EC prepared in Preparation Example 1. The size of the quartz plate is 1cm×1cm. 10μL of concentrated solution was taken with a pipette each time and coated on the quartz plate. The plate was placed in a brown screw-capped bottle in a N2 atmosphere and dried naturally at room temperature. This process was repeated three times, and a total of 30μL of OC concentrated solution was loaded to obtain a sample of EC substrate loaded with OC. The EC substrate and the sample after EC substrate loaded with OC were subjected to LDIFT-ICR MS test in positive ion mode. The test results are shown as follows. Figure 1 In addition, the test results of the blank quartz substrate loaded with OC quartz plate samples are shown as follows Figure 2 As shown. Figure 1 and 2 It can be seen that EC can not only enhance the detection of aromatic substances (polycyclic aromatic hydrocarbons and their derivatives), but also has different enhancement effects on PAHs with different structures.

[0054] Samples of OC, OC loaded on EC (EC+OC), and OC loaded on graphite (G+OC) were subjected to LDI FT-ICRMS detection and analysis. The molecular formula of the mass peaks with a signal-to-noise ratio greater than 5 was identified and their intensities were recorded. The ratio of the sum of the molecular intensities of each cluster containing odd-numbered carbon atoms to the sum of the molecular intensities of the even-numbered carbon atoms corresponded to different points, such as C37 / C38=C 37 H 14 +C 37 H 16 +C 37 H 18 +C 37 H 20 / C 38 H 14 +C 38 H 16 +C 38 H 18 +C 38 H 20 From C27 to C48, statistics were performed, C27 / C28, C29 / C30...C37 / C38...C45 / C46, C47 / C48, and each carbon cluster ratio corresponds to a point. The height of the bar graph corresponds to the ratio of the sum of the intensities of all PAHs with odd carbon numbers (C27-C48) in the mass spectrum to the sum of the intensities of all PAHs with odd carbon numbers. The results are as follows Figure 3 As shown by Figure 3 It can be seen that when the EC of the present application is used as a matrix for LDI FT-ICR MS detection, the signals of aromatic substances with odd carbon numbers (polycyclic aromatic hydrocarbons and their derivatives) can be significantly enhanced, and the enhancement effect is significantly better than that of the graphite matrix.

[0055] Example 2

[0056] The OC concentrate produced after extraction and rotary evaporation in Preparation Example 1 was coated on quartz plates with different contents of EC. The size of the quartz plates is 1cm×1cm, with one portion of EC loaded on quartz plate 1 and two portions of EC loaded on quartz plate 2. Each time, 10μL of the concentrate was taken up with a pipette and coated on quartz plates 1 and 2, which were placed in a brown screw-capped bottle in a N2 atmosphere and dried naturally at room temperature. This process was repeated three times, and a total of 30μL of OC concentrate was loaded to obtain samples with different contents of EC substrates loaded with the same amount of OC. The two samples were then tested by LDI FT-ICR MS in positive ion mode. The test results are shown in the figure below. Figure 4 As shown. Figure 4 It can be seen that the greater the EC content of the quartz plate 2 relative to that of the quartz plate 1, the stronger the enhancement effect on the substances (aromatic substances) in the OC.

[0057] Comparative Example 1

[0058] The OC concentrate produced after the extraction and rotary evaporation in Preparation Example 1 was coated on a clean quartz plate. The size of the quartz plate was 1 cm × 1 cm. 10 μL of the concentrate was pipetted onto the plate each time and then placed in a brown screw-capped bottle in an N2 atmosphere and dried naturally at room temperature. This process was repeated three times, and a total of 30 μL of OC concentrate was loaded to obtain a quartz plate loaded only with OC. The quartz plate sample loaded only with OC was subjected to LDI FT-ICRMS testing in positive ion mode. The test results are shown in Figure 2. Figure 2 shown.

[0059] The above describes the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. Application of elemental carbon in black carbon, a product of incomplete combustion in the environment, as a matrix material for laser desorption ionization mass spectrometry (LDI-MS).

2. The use according to claim 1, characterized in that The LDI-MS is detected in the positive ion mode of LDIFT-ICR MS.

3. The use according to claim 1 or 2, characterized in that The incomplete combustion product black carbon is an incomplete combustion product of environmental pollution particulate matter, fossil fuels and biomass materials.

4. The use according to any one of claims 1 to 3, characterized in that The matrix material includes a quartz plate and elemental carbon supported on the quartz plate.

5. The use according to any one of claims 1 to 4, characterized in that The matrix material is used to perform LDI-MS detection on substances containing active hydrogen; Preferably, the substance containing active hydrogen is C 27-47 Organic compounds such as C 27-47 Aromatic compounds, such as C 27-47 Polycyclic aromatic hydrocarbons and their derivatives, for example, one, two or more selected from the following compounds:

6. The use according to any one of claims 1 to 5, characterized in that The elemental carbon is prepared by the following method: The black carbon produced by incomplete combustion is washed with an organic solvent to remove the organic carbon in the black carbon to obtain elemental carbon; Preferably, the organic solvent is selected from alcohol solvents, halogenated alkane solvents, ketone solvents, ester solvents or alkane solvents, for example, one, two or more selected from methanol, ethanol, dichloromethane, chloroform, acetone, ethyl acetate and n-hexane.

7. The use according to claim 6, characterized in that Elemental carbon was prepared using the following method: Step (1): adding liquid spectrally pure n-hexane into a premixed diffusion burner and burning it to produce black carbon; Step (2): The black carbon prepared in step (1) is extracted and cleaned with an organic solvent to obtain elemental carbon.

8. The use according to claim 7, characterized in that In step (1), the black carbon produced by the diffusion flame combustion is directly deposited on the quartz plate.

9. The use according to claim 7 or 8, characterized in that In step (2), the quartz plate loaded with black carbon is soaked and cleaned using three organic solvents of different polarities; The organic solvents are dichloromethane, methanol and n-hexane respectively.

10. The use according to any one of claims 7 to 9, characterized in that In step (2), the extraction and cleaning process of dichloromethane, methanol and n-hexane is circulated for extraction and cleaning once, which is one round. The extraction process needs to be repeated for more than three rounds.

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