Titanium-based solid-phase filler, titanium-based needle type filter containing titanium-based solid-phase filler and application of titanium-based needle type filter

Abstract

The invention discloses a titanium-based solid-phase filler, a titanium-based needle type filter containing the titanium-based solid-phase filler and application of the titanium-based needle type filter. According to the invention, the titanium-based solid-phase filler is used as a functional filler and is filled in the specially-made titanium-based needle type filter for further selective treatment of the DOM sample obtained through SPE pre-enrichment, and the design plays a role in secondary selective purification in the analysis process, so that the analysis accuracy is improved. Background components of carboxylic acid and phenol oxygen-containing organic matters which are easy to ionize can be efficiently removed, the mass spectrum baseline noise is reduced, and the detection sensitivity and the quantitative reliability of soluble organic nitrides are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical fields of environmental functional materials and environmental detection technologies, and particularly relates to a titanium-based solid-phase filler, a titanium-based needle filter containing the same, and their applications. Background Art

[0002] Dissolved Organic Nitrogen Compounds (DONs) are part of the Dissolved Organic Matter (DOM) in water bodies and are widely present in various environmental media such as surface water, groundwater, domestic sewage, and industrial wastewater, usually existing at low concentrations (ng / L - μg / L). Their sources include agricultural non-point source pollution, domestic sewage discharge, industrial wastewater discharge, and natural biological processes, and they are important pollutants that cause water eutrophication and affect drinking water safety.

[0003] DONs have diverse molecular structures, including amines, amides, nitrogen-containing heterocyclic compounds, amino acids and their derivatives, etc., and usually have strong polarity, making it difficult to directly detect them through traditional liquid chromatography - mass spectrometry systems. Although in recent years, ultra-high resolution mass spectrometry (such as FT-ICR MS, Orbitrap-MS) technologies have been widely used in DOM research, due to the complex matrix and low target concentration, efficient sample pretreatment technologies are still required for enrichment and purification. Currently, common pretreatment methods mostly use Solid Phase Extraction (SPE) technology, and their targets are mostly to enrich the entire DOM system, rather than the characteristic components of DONs. Especially on commonly used fillers such as PPL, HLB, and C18, the mainly enriched substances are oxygen-containing organic compounds such as carboxylic acids and phenols. These substances not only have a rich content but are also more easily ionized under the electrospray ionization source (ESI), resulting in an overly strong signal of carboxylic acids during the analysis process, masking the mass spectrometry response of DONs.

[0004] Carboxylic acid substances are widely present in DOM, and their carboxyl structures can undergo coordination adsorption on the surface of metal oxides. Research shows that the surface of TiO2 is rich in Lewis acidic sites, which can combine with carboxylic acid functional groups through monodentate or bidentate coordination methods to form a stable Ti - OOC structure, thereby achieving high-selectivity adsorption of compounds containing carboxyl functional groups. This property can be used to selectively remove the strongly interfering carboxylic acid background components in enriched DOM samples, improving the signal-to-noise ratio and detection sensitivity of DONs in subsequent analyses.

[0005] Molecular sieve materials, especially MCM-41 (Mobil Composition of Matter No. 41) with a regular pore structure, are ideal carrier materials due to their high specific surface area, adjustable pore size, and surface modifiability. By in-situ introducing TiO2 into the pore structure of MCM-41, a TiO2 / MCM-41 composite molecular sieve material can be obtained, which has a controllable pore size distribution, good chemical affinity, and a stable interfacial structure, and is suitable for the selective adsorption and purification of carboxylic acid components in complex DOM background samples.

[0006] However, the selective adsorption ability of molecular sieve materials in the prior art for oxygen-containing organic compounds such as carboxylic acids and phenols still needs to be improved. They cannot efficiently and highly selectively adsorb carboxylic acids and phenolic oxygen-containing organic compounds simultaneously, resulting in insufficient detection sensitivity and quantitative reliability of dissolved organic nitrogen compounds during the detection process.

[0007] Therefore, there is an urgent need for a titanium-based solid-phase filler and a titanium-based needle filter containing the same that can effectively selectively adsorb carboxylic acids and phenolic oxygen-containing organic compounds, thereby improving the detection sensitivity and quantitative reliability of dissolved organic nitrogen compounds. Summary of the Invention

[0008] Object of the Invention: Aiming at the defects of the prior art, the object of the present invention is to provide a titanium-based solid-phase filler and a titanium-based needle filter containing the same and their applications that can effectively selectively adsorb carboxylic acids and phenolic oxygen-containing organic compounds, thereby improving the detection sensitivity and quantitative reliability of dissolved organic nitrogen compounds.

[0009] Technical Solution: On the one hand, the present invention provides a titanium-based solid-phase filler, which is prepared by the following steps: (1) In a reactor, tetrabutyl titanate is mixed with dodecyltrimethylammonium bromide, tetraethyl orthosilicate, isopropanol, and ultrapure water, and after sufficient stirring, a uniform sol is formed, and the pH value is adjusted using hydrochloric acid; (2) The prepared sol is aged at a certain temperature to allow TiO2 to grow and crystallize in-situ in the pore structure of MCM-41; (3) After crystallization is completed, the unreacted template agent and impurities are removed by filtration and washing, and the template agent is removed by drying and calcination to obtain TiO2 / MCM-41 molecular sieve; (4) In a reactor, TiO2 / MCM-41 molecular sieve and amino-modified silane are added, and after ultrasonic oscillation, heating reaction is carried out. After the reaction is complete, it is cooled, filtered, washed, and dried to obtain the titanium-based solid-phase filler; The amino-modified silane has the structure shown in Formula A below: .

[0010] The titanium-based solid-phase filler in the present invention can selectively absorb oxygen-containing organic compounds such as carboxylic acids and phenols accurately and efficiently. On the one hand, the TiO2 / MCM-41 molecular sieve filler can combine with carboxylic acid functional groups through monodentate or bidentate coordination to form a stable Ti-OOC structure, thereby achieving high-selectivity adsorption of carboxyl-functional group-containing compounds. On the other hand, by reacting an amino-modified silane with the TiO2 / MCM-41 molecular sieve, large steric hindrance and amino groups can be grafted onto the molecular sieve. After amino protonation, phenolate anions are electrostatically adsorbed, and phenolic compounds are selectively adsorbed through the benzene ring and the structure with large steric hindrance.

[0011] Further, in the step (1), the molar ratio of tetrabutyl titanate, dodecyltrimethylammonium bromide, tetraethyl orthosilicate, isopropanol and ultrapure water is (0.1-0.5):(0.1-0.3):(0.5-2):(1-3):(2-5), and the pH of the sol is 2-4.

[0012] Further, in the step (2), the aging temperature is 100-150 °C, and the aging time is 12-48 h.

[0013] Further, in the step (3), the drying temperature is 80-120 °C, and the drying time is 6-12 h; the calcination temperature is 350-800 °C, and the calcination time is 3-8 h.

[0014] Further, in the step (4), the heating temperature is 110-130 °C, and the reaction time is 4-6 h.

[0015] Further, the amino-modified silane is prepared through the following steps: In a reactor, a solvent, diphenylchlorosilane and acrylamide are added, heated to 40-50 °C, a platinum catalyst is added, after stirring and reacting for 3-4 hours, it is heated to 55-60 °C, after adding dilute sulfuric acid and reacting for 2-3 hours, it is cooled, filtered, washed and dried to obtain the amino-modified silane.

[0016] Further, the content of effective platinum in the platinum catalyst is 1.0×10 -5 -5.0×10 -5 ; the mass concentration of the dilute sulfuric acid is 15-25%; the molar ratio of diphenylchlorosilane and acrylamide is 1:1.2-1.5.

[0017] On the other hand, the present invention provides a titanium-based needle filter, and the titanium-based needle filter includes any one of the above titanium-based solid-phase fillers; The titanium-based needle filter includes a left liquid inlet interface, a central main body housing and a right compression knob; The titanium-based solid-phase filler is filled in the central main body housing, and the filling amount is controlled to be 3-10 mg; The pore size of the titanium-based solid-phase filler is 5-10 nm, and the overall particle size is 100-200 nm.

[0018] In the titanium-based needle filter containing the titanium-based solid-phase filler of the present invention, compared with the traditional column-structured SPE material, the titanium-based needle filter has the advantages of small volume, replaceability, strong adaptability, and suitability for rapid processing of small-volume samples. Moreover, the titanium-based material filler proposed in the present invention has the characteristics of good thermal stability, high chemical tolerance, and strong selective adsorption, overcoming the problem that the traditional filter only has a physical filtering function and cannot achieve chemical selective adsorption, and is particularly suitable for the pretreatment requirements of trace DONs in high-throughput environmental samples.

[0019] Specifically, the filling amount can be 3, 4, 5, 6, 7, 8, 9, 10 mg, the pore size of the titanium-based solid-phase filler can be 5, 6, 7, 8, 9, 10 nm, and the overall particle size can be 100, 125, 150, 175, 200 nm.

[0020] For example, the pore size of the titanium-based solid-phase filler is 7 nm, and the particle size is 150 nm.

[0021] The pore size and particle size of the titanium-based solid-phase filler in the present invention can be adjusted, which can ensure the recognition ability of medium and small molecule DONs while taking into account the filtration efficiency.

[0022] Finally, the present invention also provides an application of the above-mentioned titanium-based needle filter in detecting dissolved organic nitrogen compounds in environmental samples.

[0023] Furthermore, the specific steps for detecting dissolved organic nitrogen compounds in the environmental sample include: S1. Adjust the volume and concentration of the DOM sample pretreated by solid-phase extraction and then refrigerate it for later use; S2. After activating the titanium-based needle filter with methanol, connect it to the sample syringe for filtration and purification; S3. Inject the filtered and purified sample directly into the ultra-high resolution mass spectrometry system for mass spectrometry detection and analysis.

[0024] Beneficial effects: (1) In the present invention, by using the titanium-based solid-phase filler as the functional filler and filling it in the specially designed titanium-based needle filter, it is used for further selective treatment of the DOM sample pre-enriched by SPE. This design plays a role of secondary selective purification in the analysis process, can efficiently remove the background components of easily ionizable carboxylic acid and phenolic oxygen-containing organic compounds, reduce the mass spectrometry baseline noise, and significantly improve the detection sensitivity and quantitative reliability of dissolved organic nitrogen compounds.

[0025] (2) The titanium-based solid-phase filler provided by the present invention can selectively absorb oxygen-containing organic compounds such as carboxylic acids and phenols accurately and efficiently. On the one hand, the TiO2 / MCM-41 molecular sieve filler can combine with carboxylic acid functional groups through monodentate or bidentate coordination to form a stable Ti-OOC structure, thereby achieving high-selectivity adsorption of compounds containing carboxyl functional groups. On the other hand, by reacting an amino-modified silane with the TiO2 / MCM-41 molecular sieve, bulky steric hindrance and amino groups can be grafted onto the molecular sieve. After the amino group is protonated, it electrostatically adsorbs phenolate anions, and selectively adsorbs phenolic compounds through the benzene ring and the structure with bulky steric hindrance.

[0026] (3) The titanium-based needle filter containing the titanium-based solid-phase filler provided by the present invention has the advantages of small volume, replaceability, strong adaptability, and suitability for rapid treatment of small-volume samples compared with the traditional column-structured SPE materials. Moreover, the titanium-based material filler proposed in the present invention has the characteristics of good thermal stability, high chemical tolerance, and strong selective adsorption, overcoming the problem that traditional filters only have a physical filtration function and cannot achieve chemical selective adsorption, and is particularly suitable for the pretreatment requirements of trace DONs in high-throughput environmental samples.

[0027] (4) The titanium-based needle filter containing the titanium-based solid-phase filler provided by the present invention and its application method have a small needle structure, are adapted to standard syringes and LC-MS interfaces, facilitating batch pretreatment and field detection; can be combined with high-resolution mass spectrometry to achieve accurate quantification of trace DONs under complex DOM matrices; are suitable for sample pretreatment in various water body types and have broad potential for popularization and application. Description of the Drawings

[0028] Figure 1 It is a schematic diagram of the internal structure of the titanium-based needle filter in Example 1 of the present invention.

[0029] Figure 2 It is a schematic diagram of the use of the titanium-based needle filter of the present invention.

[0030] Figure 3 It is a high-resolution mass spectrometry comparison chart of the water sample of dissolved organic nitrogen compounds (DONs) in the present invention before and after using the titanium-based needle filter.

[0031] Figure 4 It is a Venn diagram of the data of nitrogen-containing compounds analyzed by high-resolution mass spectrometry before and after using the titanium-based needle filter in the present invention.

[0032] Figure 5 It is a high-resolution mass spectrometry comparison chart of the influent sample of a typical urban sewage treatment plant in the present invention before and after using the titanium-based needle filter.

[0033] Figure 6 For the present invention Figure 5 is a partially enlarged view. Specific embodiments

[0034] The present invention will be described below in conjunction with specific implementation schemes. It should be noted that the following examples are examples of the present invention and are only used to illustrate the present invention, rather than to limit the present invention. Other combinations and various improvements within the concept of the present invention can be made without departing from the gist or scope of the present invention.

[0035] The platinum catalyst was diluted to a mass fraction of 4.0×10 -3 purchased from J&K Scientific Ltd.; the remaining reagents and equipment are conventional reagents and equipment in the technical field of the present invention.

[0036] Preparation of amino-modified silane The amino-modified silane was prepared by the following steps: In a reactor, 100 ml of isopropanol, 0.05 mol of diphenylchlorosilane and 0.06 mol of acrylamide were added, heated to 50 °C, 0.1 ml of platinum catalyst was added, and after stirring for 4 hours, it was heated to 60 °C, and dilute sulfuric acid with a mass concentration of 20% was added and reacted for 3 hours, then cooled, filtered, washed and dried to obtain the amino-modified silane.

[0037] Example 1 The titanium-based solid-phase filler was prepared by the following steps: (1) First, tetrabutyl titanate was added to isopropanol and stirred evenly until it was completely dissolved; then dodecyltrimethylammonium bromide and tetraethyl orthosilicate were respectively added to the mixed solution and stirred continuously until completely dissolved; after adding ultrapure water, stirring was continued for 30 min to ensure the uniformity of the solution; the pH value of the solution was adjusted to 3.0 with hydrochloric acid to ensure the stability of the sol and the hydrolysis process of TiO2; after the sol was prepared, stirring was continued at room temperature for 2 h until the solution formed a uniform sol system; Among them, tetrabutyl titanate, dodecyltrimethylammonium bromide, tetraethyl orthosilicate, isopropanol and ultrapure water were in a molar ratio of 0.3:0.2:1.0:2.0:4.0; (2) Sol aging: The prepared sol was placed in a stainless steel reaction kettle with a polytetrafluoroethylene lining; the temperature control of the reaction kettle was set at 100 °C and aged for 12 h. During the aging process, TiO2 began to grow in the pores of MCM-41 and was embedded in the silicon skeleton; during the aging process, TiO2 grew in situ within the pore structure of MCM-41 to form a TiO2 / MCM-41 composite material; (3) Filtration, drying and calcination: The aged sol was filtered using a 500-mesh filter cloth to remove unreacted templating agents and impurities; it was repeatedly rinsed with deionized water until the filtrate was colorless to ensure the removal of all impurities and templating agents; afterwards, the washed TiO2 / MCM-41 composite material was placed in an oven at 100 °C for drying for 8 h until the composite material was completely dry; The dried TiO2 / MCM-41 composite material was transferred to a boat-shaped crucible and placed in a tube furnace for calcination at a temperature of 500 °C. The calcination time was 4 h to ensure the complete removal of the templating agent and the successful loading of TiO2 into the pores of MCM-41. After calcination, the pore structure of the TiO2 / MCM-41 composite molecular sieve was stable, and TiO2 was successfully loaded into the pores of MCM-41 to obtain the TiO2 / MCM-41 molecular sieve; (4) In the reactor, TiO2 / MCM-41 molecular sieve and amino-modified silane were added, ultrasonically oscillated and then heated to 120 °C for reaction for 6 h. After the reaction was complete, it was cooled, filtered, washed and dried to obtain the titanium-based solid-phase filler.

[0038] As Figure 2 shown, this example provides a titanium-based needle filter prepared based on a titanium-based solid-phase filler. This filter has a compact structure, high pressure resistance and corrosion resistance, and can be used for the selective enrichment and analysis of dissolved organic nitrogen compounds (DONs).

[0039] (1) The titanium-based needle filter mainly includes the following components: Left liquid inlet interface (liquid inlet cap): It is made of polyether ether ketone (PEEK) material, with excellent corrosion resistance and organic solvent resistance. The outside of the interface is provided with fine anti-slip threads for the quick connection or disassembly of the sampling pipeline. The standard interface size is 1 / 16 inch; Central main body housing (fixed housing): It is made of polypropylene, and the filler part has a hexagonal prism appearance for easy clamping and positioning; the inside is a hollow structure for filling the TiO2 / MCM-41 composite molecular sieve material; the surface is treated by anodic oxidation or passivation to enhance corrosion resistance and weather resistance; Right pressing knob (locking screw): It is made of SUS304 stainless steel, and the surface is treated with rust prevention and has anti-slip knurled patterns. This component has the dual functions of pressing the internal solid-phase filler and serving as a direct connection interface for the sampling needle. A standard sampling needle insertion port is reserved inside, and a sampling needle with a diameter of 0.5 - 0.8 mm can be directly inserted, and airtight connection is achieved by screwing to facilitate quick sampling into the filter; (2) The packing is a titanium-based solid-phase packing; a material with a pore size of about 7 nm and a particle size of about 150 nm is selected; it is filled in the hexagonal internal cavity of the central main body housing; the filling amount is controlled to be 5 mg, and it is densely packed by means of micro-vibration assistance; during the filling process, it is kept uniform to avoid obvious packing layer or channel bypass phenomenon; (3) A stainless steel microporous filter with a pore size of 10 μm is provided at each of the left and right ends to support the solid-phase packing and prevent loss; the left liquid inlet cap and the right pressing knob are threadedly locked to form a stable and tight packaging structure.

[0040] Performance test 1. The titanium-based needle filter of the present invention is applied to the detection of dissolved organic nitrogen compounds (DONs) in water samples. This method can effectively remove interfering compounds, selectively enrich dissolved organic nitrogen compounds, and improve the detection sensitivity by applying the titanium-based needle filter to enrich the DOM sample after solid-phase extraction (SPE) treatment.

[0041] Specifically, it includes the following steps: (1) Sample information: The surface water sample collected from Qingnian Lake (117.17°E, 39.11°N) on the Weijin Road Campus of Tianjin University is selected as the implementation sample. The sampling point is 0.5 m below the lake surface and 2.0 m away from the lake shore.

[0042] (2) Sample pretreatment: Take 200 mL of the above water sample and filter it with a 0.45 μm filter membrane to remove large particulate suspensions. Subsequently, hydrochloric acid is added to adjust the pH value of the filtered water sample to 2. Then, the DOM in the water sample is enriched by a PPL type solid-phase extraction column (500 mg, 6 mL). After the enrichment is completed, the enriched DOM sample is dried to 1 mL with nitrogen to facilitate the subsequent detection.

[0043] (3) Use of the titanium-based needle filter: Take out the titanium-based needle filter in Example 1 of the present invention and wash and activate it with 5 mL of methanol to remove residual impurities. Its use schematic diagram is as Figure 2 shown. One end of this filter is a sampling needle connector, which supports the direct insertion of the sampling needle; the other end is a PEEK tube connector, which can be connected to the ionization source of a high-resolution mass spectrometer through a PEEK tube.

[0044] (4)Mass spectrometry acquisition: The water sample treated by SPE and concentrated is aspirated into the injection needle, and then connected to the titanium-based needle filter, PEEK tube, and mass spectrometry ion source in sequence. The flow rate of the injection needle is set to 0.30 mL / h. High-resolution mass spectrometry analysis is carried out using the positive ion mode (+) of the electrospray ionization source (ESI) of FT-ICR MS. At m / z 400, the mass resolution of FT-ICR MS is 450,000. Broadband 4M acquisition is adopted, the mass acquisition range is m / z 150 - 1000, and the spectra are stacked 256 times.

[0045] Meanwhile, under the same experimental conditions, mass spectrometry data of a sample without connecting the titanium-based needle filter is collected for comparative analysis.

[0046] The specific operation is as follows: After directly aspirating the water sample treated by SPE and concentrated into the injection needle, it is directly connected to the mass spectrometry ion source through the PEEK tube. Parameters such as the flow rate of the injection needle, mass spectrometry analysis mode, mass resolution, acquisition range, and spectra stacking times are kept consistent with the previous steps to ensure the comparability of the comparative data.

[0047] (5)Data analysis: After the sample test is completed, the data is recalibrated using the internal reference mass table. After internal calibration, ensure that the mass error does not exceed 600 ppb throughout the mass range. Select mass spectrometry peaks with a signal-to-noise ratio higher than 6, and assign accurate chemical formulas to the compounds according to the specific numbers of carbon, hydrogen, oxygen, nitrogen, and sulfur atoms to generate a detailed list of molecular masses and chemical formulas. Among them, the number of carbon atoms is 1 - 80, the number of hydrogen atoms is 2 - 120, the number of oxygen atoms is 0 - 25, the number of nitrogen atoms is 0 - 3, and the number of sulfur atoms is 0 - 2.

[0048] (6)Experimental results and analysis: The experimental results are as Figure 3 and Figure 4 shown.

[0049] Figure 3 is a high-resolution mass spectrometry comparison chart of the water sample of dissolved organic nitrogen compounds (DONs) before and after using the titanium-based needle filter. The results show that after treatment with the titanium-based needle filter, carboxylic acids, phenolic oxygen-containing organic compounds such as CHO and CHOS, and Na-containing compounds in the original DOM sample are effectively removed, indicating that the filter has a significant removal effect on these compounds. After removing these interfering compounds, the detection signals of CHN, CHNO, and CHNOS compounds are significantly enhanced. Figure 4 is a Venn diagram of high-resolution mass spectrometry analysis data of nitrogen-containing compounds before and after using the titanium-based needle filter. It can be seen from the figure that after using the titanium-based needle filter, 3732 nitrogen-containing compounds are detected more, accounting for 43.24% of the total. Only 47.61% of the nitrogen-containing compounds cannot be detected because they contain carboxyl groups and are adsorbed by the filter.

[0050] 2. The titanium-based needle filter system provided by the present invention is used to enrich and analyze DONs in the influent samples of a typical urban sewage treatment plant.

[0051] Specifically, it includes the following steps: (1) Sample information: At the inlet of a large sewage treatment plant, an untreated raw water sample is collected.

[0052] (2) Sample pretreatment: Take 50 mL of the above water sample, filter it with a 0.45 μm filter membrane to remove large particulate suspensions. Subsequently, add hydrochloric acid to adjust the pH value of the filtered water sample to 2. Then, enrich DOM in the water sample through a PPL solid-phase extraction column (200 mg, 3 mL). After enrichment, use nitrogen to blow dry the enriched DOM sample to 1 mL for subsequent detection.

[0053] (3) Use of the titanium-based needle filter: Take out the titanium-based needle filter of Example 1 of the present invention, wash and activate it with 5 mL of methanol to remove residual impurities. Its usage schematic diagram is as Figure 2 shown. One end of this filter is a sampling needle connector, which supports the direct insertion of the sampling needle; the other end is a PEEK tube connector, which can be connected to the ionization source of a high-resolution mass spectrometer through a PEEK tube.

[0054] (4) Mass spectrometry acquisition: Inhale the water sample treated and concentrated by SPE into the sampling needle, connect the titanium-based needle filter, PEEK tube and mass spectrometry ion source in sequence, and set the flow rate of the sampling needle to 0.30 mL / h. Use the electrospray ionization source (ESI) positive ion mode (+) of FT-ICR MS for high-resolution mass spectrometry analysis. At m / z 400, the mass resolution of FT-ICR MS is 450,000. Adopt broadband 4M acquisition, the mass acquisition range is m / z 150 - 1000, and the spectra are stacked 256 times.

[0055] At the same time, under the same experimental conditions, collect mass spectrometry data without connecting the titanium-based needle filter for comparative analysis. The specific operation is as follows: After directly inhaling the water sample treated and concentrated by SPE into the sampling needle, directly connect it to the mass spectrometry ion source through a PEEK tube. Parameters such as the flow rate of the sampling needle, the mass spectrometry analysis mode, the mass resolution, the acquisition range and the number of spectra stacking are kept consistent with the previous steps to ensure the comparability of the comparative data.

[0056] (5)Data analysis: After the sample test is completed, the data is recalibrated using the internal reference mass table. After internal calibration, ensure that the mass error does not exceed 600 ppb within the entire mass range. Select the mass spectrometry peaks with a signal-to-noise ratio higher than 6, and assign accurate chemical formulas to the compounds based on the specific numbers of carbon, hydrogen, oxygen, nitrogen, and sulfur atoms to generate a detailed list of molecular masses and chemical formulas. Among them, the number of carbon atoms is 1 - 80, the number of hydrogen atoms is 2 - 120, the number of oxygen atoms is 0 - 25, the number of nitrogen atoms is 0 - 3, and the number of sulfur atoms is 0 - 2.

[0057] (6)Experimental results and analysis: The experimental results are as Figure 5 shown.

[0058] Figure 5 This is a high-resolution mass spectrometry comparison chart of the influent sample of a typical urban sewage treatment plant in the present invention before and after using a titanium-based needle filter. The results show that the original wastewater DOM sample contains typical surfactants, and their strong polarity generates a series of strong peaks within the entire mass detection range, seriously masking the mass spectrometry signals of DOM compounds. After treatment with the titanium-based needle filter, these surfactants are significantly removed. For example, in the local enlarged view of the mass spectrometry point at m / z 371, the detection results of the nitrogen-containing compound peak can be clearly observed, indicating that the filter effectively reduces interference and improves the detection sensitivity of nitrogen-containing compounds.

[0059] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable those who are familiar with this technology to understand the content of the present invention and implement it. It should not be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A titanium-based solid-phase filler, characterized in that, It is prepared by the following steps: (1) In a reactor, tetrabutyl titanate is mixed with dodecyltrimethylammonium bromide, tetraethyl orthosilicate, isopropanol and ultrapure water, and after sufficient stirring, a uniform sol is formed, and the pH value is adjusted with hydrochloric acid; (2) The prepared sol is aged at a certain temperature to enable the in-situ growth and crystallization of TiO2 in the pore structure of MCM-41; (3) After the crystallization is completed, the unreacted template agent and impurities are removed by filtration and washing, and the template agent is removed after drying and calcination to obtain TiO2 / MCM-41 molecular sieve; (4) In a reactor, TiO2 / MCM-41 molecular sieve and amino-modified silane are added, and after ultrasonic oscillation, the reaction is heated. After the reaction is complete, it is cooled, filtered, washed and dried to obtain the titanium-based solid phase filler; The amino-modified silane has the structure shown in Formula A below: 。 2. The titanium-based solid-phase filler according to claim 1, wherein In the step (1), the molar ratio of tetrabutyl titanate, dodecyltrimethylammonium bromide, tetraethyl orthosilicate, isopropanol and ultrapure water is (0.1-0.5):(0.1-0.3):(0.5-2):(1-3):(2-5), and the pH of the sol is 2-4.

3. The titanium-based solid-phase filler according to claim 1, wherein In the step (2), the aging temperature is 100-150 °C and the aging time is 12-48 h.

4. The titanium-based solid-phase filler according to claim 1, characterized in that, In the step (3), the drying temperature is 80-120 °C and the drying time is 6-12 h; the calcination temperature is 350-800 °C and the calcination time is 3-8 h.

5. The titanium-based solid-phase filler according to claim 1, wherein, In the step (4), the heating temperature is 110-130 °C and the reaction time is 4-6 h.

6. The titanium-based solid-phase filler according to claim 1, wherein The amino-modified silane is prepared by the following steps: In a reactor, a solvent, diphenylchlorosilane and acrylamide are added, heated to 40-50 °C, a platinum catalyst is added, and after stirring and reacting for 3-4 hours, it is heated to 55-60 °C, and after adding dilute sulfuric acid and reacting for 2-3 hours, it is cooled, filtered, washed and dried to obtain the amino-modified silane.

7. The titanium-based solid-phase filler according to claim 6, wherein The content of effective platinum in the platinum catalyst is 1.0×l0 -5 -5.0×l0 -5 ; the mass concentration of the dilute sulfuric acid is 15-25%; the molar ratio of diphenylchlorosilane to acrylamide is 1:1.2-1.

5.

8. A titanium-based needle filter, characterized in that, The titanium-based needle filter comprises the titanium-based solid phase filler according to any one of claims 1-7; The titanium-based needle filter includes a left liquid inlet interface, a central main body housing and a right pressing knob; The titanium-based solid phase filler is loaded in the central main body housing, and the loading amount is controlled to be 3-10 mg; The pore diameter of the titanium-based solid phase filler is 5-10 nm, and the overall particle size is 100-200 nm.

9. Use of the titanium-based needle filter according to claim 8 in detecting dissolved organic nitrogen compounds in environmental samples.

10. The application according to claim 9, characterized in that, The specific steps for detecting dissolved organic nitrogen compounds in environmental samples include: S1. Adjust the volume and concentration of the DOM sample pretreated by solid phase extraction and then refrigerate it for standby; S2. After activating the titanium-based needle filter with methanol, connect it to a sample syringe for filtration and purification treatment; S3. Inject the filtered and purified sample directly into an ultra-high resolution mass spectrometry system for mass spectrometry detection and analysis.

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