In-source cracking controllable pulse direct-current arc induced nano-liter electrospray ionization source and mass spectrum combined system and detection method

Abstract

The invention discloses an in-source cracking controllable pulse direct-current arc induced nano-liter electrospray ionization source and mass spectrum combined system and a detection method. The system comprises a mass spectrum, a quartz capillary tube, a metal coil, a positive wire, a negative wire and a direct-current arc generator. The high charge density characteristic of pulse direct-current arc plasma and the solution polarization effect induced by a metal coil are combined to construct a dual-drive ionization system. Under low voltage, molecular ion integrity is maintained; under high voltage, the characteristic fragment ion strength is obviously enhanced, the compound structure information can be obtained without depending on tandem mass spectrometry, and the problems of time consumption and sample consumption of nanoliter electrospray ionization source analysis are effectively solved. The pulse direct-current arc provides high-density positive and negative charges, the metal coil strengthens directional migration of charged species to the tip of the capillary tube through potential difference, and ionization stability and efficiency are remarkably improved.

Description

TECHNICAL FIELD

[0001] The application relates to a pulsed direct current arc induced nano-electrospray ionization source with controllable in-source fragmentation, a mass spectrometry system and a detection method, and belongs to the field of analytical chemistry. BACKGROUND

[0002] Nano-electrospray ionization (nano-ESI) is an ionization technique based on ultra-low flow rate and sub-micron droplet size, which has high ionization efficiency and good sample saving characteristics, and is especially suitable for micro-sample detection at the picoliter to nanoliter level (Anal. Chem. 1996, 68(1), 1-8). The technique has been widely used in the fields of metabolomics, proteomics and natural product screening (Nat. Chem. Biol. 2014, 10(11), 963-968). However, as a soft ionization method, the traditional nano-ESI is usually dominated by producing intact quasi-molecular ions, and can only provide basic information such as molecular weight and molecular formula, and it is difficult to directly obtain specific structural information. Structural analysis often needs to rely on tandem mass spectrometry (TrAC, Trends Anal. Chem. 2015, 69, 24-33), and the analysis time is relatively long and the sample consumption is relatively large.

[0003] In-source fragmentation (ISF) provides a potential solution to the above problems. ISF refers to the phenomenon that chemical bonds are broken due to excess energy or unstable molecular structure during ionization, thereby directly generating fragment ions in the ion source. Although ISF may cause the parent ion signal to decrease and affect the detection sensitivity, the fragment ions generated by ISF can provide direct structural information. Therefore, some studies have attempted to use ISF for structure analysis of substances. For example, Almasian et al. developed a low-temperature plasma ion source with dual-mode ISF function, which showed advantages in organic compound identification and gas-phase reaction research (Rapid Commun. Mass Spectrom. 2010, 24(6), 742-748). Zhu et al. proposed a fragmentation device based on arc plasma, which utilized the high energy, high temperature and unique chemical activity of the alternating current arc plasma to fragment neutral molecules or ions, while obtaining structural and molecular weight information (Anal. Chem. 2020, 92(21), 14633-14639). Tang et al. used ISF to characterize perfluoro and polyfluoroalkyl substances, and achieved targeted and non-targeted screening through fragment ions (npj Clean Water 2023, 6(1), 6). Huang et al. also designed a thermal coupling charge ionization device, which showed hard ionization characteristics when the temperature was higher than 400℃, and could generate fragment ions that were helpful for isomer differentiation (Anal. Chem. 2024, 96(48), 19012-19020). The above studies show that ISF has important application prospects in molecular structure analysis.

[0004] It is worth noting that arc discharge, as a strong thermal plasma source, can produce highly excited states beyond the energy limits of conventional chemical or photochemical processes (J. Am. Chem. Soc. 1955, 77(9), 2351-2361). These excited states can promote the decomposition of organic compounds through various fragmentation pathways (Plasma Chem. Plasma Process. 1983, 3(1), 1-61), providing a new idea for the development of ISF technology based on arc plasma. SUMMARY

[0005] The present application provides a pulsed direct current arc-induced nanoliter electrospray ionization source with controllable in-source fragmentation, a mass spectrometry system and a detection method.

[0006] This invention develops a pulsed DC arc-induced nanoliter electrospray ionization source with controllable in-source fragmentation. It utilizes the high-density positive and negative charges provided by the arc plasma to charge the analyte, and then enhances the directional migration of charged ions to the capillary tip through the potential difference of the metal coil, significantly improving ionization stability and efficiency. Simultaneously, by adjusting the output voltage to influence the energy of the arc plasma, the in-source fragmentation behavior can be controlled; at low voltage, the integrity of molecular ions is maintained, while at high voltage, the intensity of characteristic fragment ions is significantly enhanced. Furthermore, the plasma microdroplet system constructed by this device can promote the reaction of HO· and H4O2. +· The generation of these functional groups enables the functionalization of drug molecules. To achieve the above-mentioned objectives, the technical solution adopted by this invention is as follows:

[0007] A pulsed DC arc-induced nanoliter electrospray ionization source coupled with mass spectrometry, with controllable in-source fragmentation, comprises:

[0008] Mass spectrometry;

[0009] A capillary tube is installed at the inlet of the mass spectrometer;

[0010] A metal coil wound around the capillary;

[0011] A positive electrode wire, wherein the positive electrode wire is directly connected to the end of the metal coil away from the mass spectrometer;

[0012] A negative electrode wire, wherein the negative electrode wire is connected at a distance from the end of the metal coil near the mass spectrometer;

[0013] A DC arc generator, wherein the DC arc generator is connected to the positive and negative conductors.

[0014] This invention combines the high charge density of pulsed DC arc plasma with the solution polarization effect induced by a metal coil to construct a dual-drive ionization system. At low voltage, the integrity of molecular ions is maintained; at high voltage, the intensity of characteristic fragment ions is significantly enhanced. Compound structural information can be obtained without relying on tandem mass spectrometry, effectively solving the problems of time-consuming analysis and sample consumption in nanoliter electrospray ionization sources. The pulsed DC arc provides a high density of positive and negative charges, while the metal coil enhances the directional migration of charged species to the capillary tip through potential difference, significantly improving ionization stability and efficiency. It overcomes the limitations of traditional nanospray ionization, which is characterized by "soft ionization and few fragments," by precisely adjusting the output voltage to control the degree of fragmentation within the source. Furthermore, the unique reaction environment formed by the pulsed DC arc and microdroplets induces efficient hydroxyl functionalization modification of drug molecules, providing a novel experimental platform for drug molecule structure modification and active derivative screening.

[0015] The sample outlet of the capillary is aligned with the sample inlet of the mass spectrometer, and the distance between the sample outlet of the capillary and the sample inlet of the mass spectrometer is 1 to 30 mm.

[0016] The sample outlet of the capillary is a pointed tip, and the inner diameter of the tip is between 1 μm and 500 μm.

[0017] The diameter of the metal wire in the metal coil is 0.1 to 5 mm; the number of turns in the metal coil is 2 to 200.

[0018] The negative electrode wire is connected to the end of the metal coil near the mass spectrometer at a distance of 0.1 to 5 cm.

[0019] The capillary can be one or more, and when there are multiple capillary tubes, each capillary tube adopts an array structure.

[0020] A coaxial inner tube is provided inside the capillary, and the sample outlet of the inner tube is flush with the sample outlet of the capillary.

[0021] A systematic detection method includes the following steps:

[0022] a) Draw the solution to be tested into the capillary tube;

[0023] (b) Start the DC arc generator, boosting the daily 220V AC power to 1-100kV. An arc discharge occurs in the gap between the negative electrode wire and the metal coil, generating plasma, which causes the solution to be tested to produce charged ions. Simultaneously, the potential difference generated by the metal coil promotes the directional movement of charged ions. After the ions accumulate at the capillary tip, electrospray is generated, and the plasma enters the mass spectrometer for detection. When the solution to be tested is a mixture of methanol and water containing drug molecules, it will react with H₂O· and H₄O₂. +· Under the influence of [something], a polyhydroxy oxidation reaction occurs.

[0024] This invention provides a pulsed DC arc-induced nano-liter electrospray ionization source with controllable in-source pyrolysis. The source induces nano-liter electrospray to generate charged microdroplets through arc plasma. The non-contact induced electrospray avoids the electrochemical and capillary blockage phenomena present in conventional nano-liter electrospray ionization, and represents a novel plasma-microdroplet system.

[0025] Furthermore, a method for detecting the use of a pulsed DC arc-induced nanoliter electrospray ionization source with controllable in-source splitting includes the following steps:

[0026] a) The sample solution is drawn into the quartz capillary tube by capillary action. The quartz capillary tube passes through the center of the metal coil. A certain length of wire is reserved at both ends of the metal coil, and the front end of the metal coil is aligned with the transition point of the inner diameter of the quartz capillary tube.

[0027] b) The DC arc generator is connected to the rear end of the metal coil via a positive wire, and the negative wire is spaced a certain distance from the front end of the metal coil;

[0028] c) Start the DC arc generator to boost the daily 220V AC power to 1-100kV, and generate an arc discharge in the negative conductor and the front end of the metal coil to produce plasma.

[0029] d) The potential difference generated before and after the metal coil promotes the directional movement of charged ions. When a certain number of ions accumulate at the tip of the quartz capillary, electrospray is generated, and the abundant active species generated by the plasma act on the electrospray region.

[0030] e) The synergistic effect of arc plasma and microdroplets promotes the reaction of HO· and H4O2. +· The generation of active species accelerates their oxidation reaction, generating polyhydroxy oxidized drug molecules.

[0031] The arc plasma can be replaced by various forms of plasma such as Tesla discharge and corona discharge.

[0032] The quartz capillary can be arranged in an array, with 2 to 10 capillary bundles arranged together and passing through a metal coil. By rotating the capillary group and starting the DC arc generator, multiple capillary tubes can generate electrospray simultaneously, thereby enabling rapid analysis of multiple samples and collecting reaction products generated during the spraying process.

[0033] The quartz capillaries can be arranged in an array and inserted into multiple metal coils, which are connected in series and one end is connected to the negative electrode wire. By moving different capillaries, multiple sets of samples can be quickly switched and arrayed for analysis.

[0034] The quartz capillary can be equipped with a coaxial sleeve structure, with different sample solutions introduced into the two tubes respectively, thereby achieving a two-phase reaction during the spraying process.

[0035] In a preferred embodiment, the diameter of the quartz capillary tip is on the order of nm to μm, and the distance between it and the mass spectrometer inlet is 1 to 30 mm.

[0036] In a preferred embodiment, the metal coil material includes, but is not limited to, silver, copper, gold, aluminum, niobium, nickel, iron, tungsten, zirconium, and titanium; the diameter of the metal wire is 0.1–5 mm; and the number of coil turns is 2–200.

[0037] In a preferred embodiment, the distance between the negative electrode wire and the metal coil is 0.1 to 4.0 cm.

[0038] Compared with existing nano-ESI technology, the present invention has the following significant advantages:

[0039] 1. It can analyze samples with low to medium polarity, thus expanding the detection range of nano-ESI;

[0040] 2. It can induce intrasource fragmentation of analytes and effectively control the degree of intrasource fragmentation by adjusting the voltage;

[0041] 3. Can promote the reaction of HO· and H4O2 +· The generation of active species accelerates the oxidation of drug molecules, thereby achieving drug functionalization.

[0042] 4. It has good stability and can be used for the quantitative analysis of amino acids. Attached Figure Description

[0043] Figure 1 This invention relates to a schematic diagram of a pulsed DC arc-induced nanoliter electrospray ionization source with controllable in-source splitting;

[0044] Figure 2 This invention relates to a pulsed DC arc-induced nanoliter electrospray ionization source device with controllable in-source splitting;

[0045] Figure 3 The results are the analytical results of dioctyl phthalate, testosterone, 1,2-naphthoquinone, bergamot lactone, sronandrolone, ethyl n-octanoate, ethyl decanoate, and diethyl phthalate in Example 1 of this invention.

[0046] Figure 4 The results are the analytical results of leucine, proline, isoleucine, histidine, alanine, phenylalanine, methionine, tyrosine, and glutamic acid in Example 2 of the present invention.

[0047] Figure 5 The results of the analysis of proline, cefoperazone and telmisartan under 15kV and 22kV conditions in Example 3 of the present invention are as follows:

[0048] Figure 6 This is the analytical result of reserpine in Example 4 of the present invention;

[0049] Figure 7 This is the standard curve for analyzing five amino acid fragment ions in Example 5 of this invention. Detailed Implementation

[0050] The present invention will be further described below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following description.

[0051] like Figure 1 and Figure 2As shown, this invention provides a schematic diagram and a photograph of a source-controlled pulsed DC arc-induced nanoliter electrospray ionization source with controllable in-source splitting. A system combining a source-controlled pulsed DC arc-induced nanoliter electrospray ionization source with a mass spectrometer includes: a mass spectrometer; a capillary 1 disposed at the inlet of the mass spectrometer; a metal coil 2 wound around the capillary 1; a positive electrode wire 4 directly connected to the end of the metal coil 2 furthest from the mass spectrometer; a negative electrode wire 5 spaced apart from the end of the metal coil 2 near the mass spectrometer; and a DC arc generator 3 connected to the positive electrode wire 4 and the negative electrode wire 5.

[0052] The quartz capillary tip used in this invention has a tip diameter in the range of nm to μm and an inner diameter in the range of 1 μm to 500 μm. The sample outlet of the capillary 1 faces the sample inlet of the mass spectrometer, and the two are flush. The distance between the sample outlet of the capillary 1 and the sample inlet of the mass spectrometer is 1 to 30 mm.

[0053] The metal coil materials used in this invention include, but are not limited to, silver, copper, gold, aluminum, niobium, nickel, iron, tungsten, zirconium, and titanium; the diameter of the metal wire is 0.1–5 mm; and the number of coil turns is 2–200.

[0054] In this invention, the negative electrode wire 5 is connected to the metal coil 2 at a distance of 0.1 to 5 cm from the end near the mass spectrometer. More preferably, the distance between the negative electrode wire and the metal coil is 0.1 to 4.0 cm.

[0055] The arc plasma used in this invention can be replaced by various forms of plasma such as Tesla discharge and corona discharge.

[0056] The quartz capillary used in this invention can be arranged in an array structure, with 2 to 10 capillary bundles arranged together and passing through a metal coil. By rotating the capillary group and starting the DC arc generator, multiple capillary tubes can generate electrospray simultaneously, thereby enabling rapid analysis of multiple samples and can also be used to collect reaction products generated during the spraying process.

[0057] The quartz capillaries used in this invention can be arranged in an array and inserted into multiple metal coils. The metal coils are connected in series and one end is connected to the negative electrode wire. By moving different capillaries, multiple sets of samples can be quickly switched and arrayed for analysis.

[0058] The quartz capillary used in this invention can be equipped with a coaxial sleeve structure inside, and different sample solutions can be introduced into the two tubes respectively, thereby realizing a two-phase reaction during the spraying process.

[0059] A method for installing and using a pulsed DC arc-induced nanoliter electrospray ionization source with controllable in-source pyrolysis includes the following steps:

[0060] a) The sample solution is drawn into the quartz capillary tube 1 by capillary action. The quartz capillary tube passes through the center of the metal coil 2. A certain length of wire is reserved at both ends of the metal coil 2, and the front end of the metal coil 2 is aligned with the transition point of the inner diameter of the quartz capillary tube 1.

[0061] b) The DC arc generator 3 is connected to the rear end of the metal coil via the positive wire 4, and the negative wire 5 is spaced a certain distance from the front end of the metal coil 2;

[0062] c) Start the DC arc generator 3 to boost the daily 220V AC power to 1-100kV, and generate an arc discharge in the negative conductor and the front end of the metal coil to produce plasma.

[0063] d) The potential difference generated before and after the metal coil 2 promotes the directional movement of charged ions. When the ions accumulate to a certain number at the tip of the quartz capillary 1, electrospray is generated, and the abundant active species generated by the plasma act on the electrospray region.

[0064] e) The synergistic effect of arc plasma and microdroplets promotes the reaction of HO· and H4O2. +· The generation of active species accelerates their oxidation reaction, generating polyhydroxy oxidized drug molecules.

[0065] The technical effects achievable by the pulsed DC arc-induced nano-liter electrospray ionization source with controllable in-source pyrolysis described in this invention will be further illustrated below with specific application examples.

[0066] Example 1

[0067] use Figure 1 The apparatus shown is coupled with a mass spectrometer (LCQ Fleet mass spectrometer) to analyze low- to intermediate-level compounds. The specific operation is as follows:

[0068] The mass spectrometer was used in full scan mode with the following parameters: scan range 50–1000 Da, capillary voltage 25 V, capillary temperature 275 °C, lens voltage 75 V, and sheath gas flow rate, auxiliary gas flow rate, and purge gas flow rate all 0. Under the experimental conditions, each scan lasted 30 ms.

[0069] A single-tube structure is adopted, in which the sample solution is drawn into a quartz capillary with an inner diameter of 50μm through capillary action. The quartz capillary is then threaded into a metal coil with 15 turns made of copper wire with a diameter of 0.2mm, and placed on a 3D moving platform.

[0070] The sample solutions were mixed solutions of methanol and water containing the sample (volume ratio of methanol to water was 2:3). The samples were dioctyl phthalate, testosterone, 1,2-naphthoquinone, bergamot lactone, sronandrolone, ethyl n-octanoate, ethyl decanoate, and diethyl phthalate. Eight samples corresponded to eight sample solutions, which were drawn into quartz capillaries for detection.

[0071] Connect the positive lead to the rear end of the metal coil, and leave the negative lead 1.5cm away from the front end of the metal coil;

[0072] The DC arc generator is started, and the daily 220V AC power is boosted to 17kV through a small circuit board, which generates an arc discharge at the front end of the negative conductor and the metal coil, producing abundant plasma.

[0073] Figure 3 The results are from the analysis of eight low- to medium-polarity compounds using the source-controlled pulsed DC arc-induced nano-liter electrospray ionization source described in this invention. The spectra of dioctyl phthalate, testosterone, 1,2-naphthoquinone, bergamot lactone, and sronandrolone, ethyl n-octanoate, ethyl decanoate, and diethyl phthalate all showed clear target analyte signals, indicating that the source-controlled pulsed DC arc-induced nano-liter electrospray ionization source described in this invention has a good ionization effect on low- to medium-polarity compounds.

[0074] Example 2

[0075] use Figure 1 The apparatus shown is coupled with a mass spectrometer (LCQ Fleet mass spectrometer) for the analysis of amino acids. The specific operation is as follows:

[0076] The mass spectrometer was used in full scan mode with the following parameters: scan range 50–1000 Da, capillary voltage 25 V, capillary temperature 275 °C, lens voltage 75 V, and sheath gas flow rate, auxiliary gas flow rate, and purge gas flow rate all 0. Under the experimental conditions, each scan lasted 30 ms.

[0077] A single-tube structure is used to draw a 20 μg / mL methanol-water mixture (methanol to water volume ratio of 2:3) into a quartz capillary tube for detection. The mixture contains 9 samples: leucine, proline, isoleucine, histidine, alanine, phenylalanine, methionine, tyrosine, and glutamic acid. Each sample has its own methanol-water mixture and is drawn into the capillary tube for detection. The capillary tube is then threaded through a metal coil made of 0.3 mm diameter copper wire and placed on a 3D moving platform.

[0078] Connect the positive lead to the rear end of the metal coil, and leave the negative lead 1.0 cm away from the front end of the metal coil;

[0079] The DC arc generator is started, and the daily 220V AC power is boosted to 22kV through a small circuit board, which generates an arc discharge at the front end of the negative conductor and the metal coil, producing abundant plasma.

[0080] Figure 4 The results are from the analysis of nine amino acids using the source-controlled pulsed DC arc-induced nanoliter electrospray ionization source described in this invention. The mass spectrometry results of the nine amino acids consistently show the presence of protonated molecular ion peaks ([M+H)). + It also contains characteristic fragment ions with a 46 Da mass difference. This cleavage originates from the breakage of the carboxyl group, leading to the loss of formic acid and the formation of [M+H-HCOOH]. + Furthermore, fragment ions with mass differences of 17 and 18 Da were observed, corresponding to the loss of ammonia and water, respectively, forming [M+H-NH3]. + and [M+H-H2O] + The above results demonstrate that the pulsed DC arc-induced nanoliter electrospray ionization source with controllable in-source pyrolysis described in this invention can generate fragment ions and achieve in-source pyrolysis even without applying additional collision energy.

[0081] Example 3

[0082] use Figure 1 The apparatus shown was coupled with a mass spectrometer (LCQ Fleet mass spectrometer) to analyze proline, cefoperazone, and telmisartan. The specific operation is as follows:

[0083] The mass spectrometer was used in full scan mode with the following parameters: scan range 50–1000 Da, capillary voltage 30 V, capillary temperature 300 °C, lens voltage 100 V, and sheath gas flow rate, auxiliary gas flow rate, and purge gas flow rate all 0. Under the experimental conditions, each scan lasted 30 ms.

[0084] Using a single-tube structure, a quartz capillary tube with a tip inner diameter of 60 μm is drawn into the system via capillary action. The solutions are: a 100 μg / mL proline solution in methanol and water (volume ratio of methanol to water: 2:3), a 100 μg / mL cefoperazone solution in methanol and water (volume ratio of methanol to water: 2:3), and a 100 μg / mL telmisartan solution in methanol and water (volume ratio of methanol to water: 2:3). The capillary tube is then threaded through a 12-turn metal coil made of 0.2 mm diameter copper wire and placed on a 3D moving platform.

[0085] Connect the positive lead to the rear end of the metal coil, and the negative lead to the front end of the metal coil at a distance of 2.0 cm;

[0086] The DC arc generator is activated, and the daily 220V AC power is boosted to 15kV and 22kV through a small circuit board. Arc discharge occurs at the negative conductor and the front end of the metal coil, generating abundant plasma.

[0087] Figure 5 The analytical results for proline, cefoperazone, and telmisartan were obtained using the source-controlled pulsed DC arc-induced nanoliter electrospray ionization source described in this invention, under conditions of 15 kV and 22 kV. Figure 5 In A, proline produces fragment ions with m / z 70.0, and their intensity increases from 1.16 × 10⁻⁶ at 15 kV. 3 2.48×10 when upgraded to 22kV 3 .exist Figure 5 In component B, cefoperazone produces fragment ions with an m / z of 530.1, the intensity of which increases with voltage from 1.62 × 10⁻⁶. 3 Increased to 3.03×10 3 .and Figure 5 In C, telmisartan showed almost no fragmentation at 15 kV, but significant fragmentation occurred at 22 kV at m / z 305.3. These results demonstrate that the pulsed DC arc-induced nano-liter electrospray ionization source with controllable in-source fragmentation described in this invention can regulate the degree of fragmentation by adjusting the voltage.

[0088] Example 4

[0089] use Figure 1 The apparatus shown was coupled with a mass spectrometer (LCQ Fleet mass spectrometer) to analyze reserpine. The specific operation is as follows:

[0090] The mass spectrometer was used in full scan mode with the following parameters: scan range 50–1000 Da, capillary voltage 25 V, capillary temperature 275 °C, lens voltage 75 V, and sheath gas flow rate, auxiliary gas flow rate, and purge gas flow rate all 0. Under the experimental conditions, each scan lasted 30 ms.

[0091] Using a single-tube structure, reserpine solution (with a methanol / water volume ratio of 2 / 3) is drawn into a quartz capillary with an inner diameter of 30 μm through capillary action. The quartz capillary is then threaded into a 14-turn metal coil made of copper wire with a diameter of 0.2 mm and placed on a 3D moving platform.

[0092] Connect the positive lead to the rear end of the metal coil, and leave the negative lead 1.5cm away from the front end of the metal coil;

[0093] The DC arc generator is started, and the daily 220V AC power is boosted to 17kV through a small circuit board, which generates an arc discharge at the front end of the negative conductor and the metal coil, producing abundant plasma.

[0094] Figure 6 The results are from the analysis of reserpine using the source-controlled pulsed DC arc-induced nanoliter electrospray ionization source described in this invention. Figure 6 In addition to the protonation signal of reserpine (m / z 609.4), several consecutive ion peaks with a mass difference of 16 Da also appeared. In this invention, the pulsed DC arc plasma and microdroplets work synergistically to promote the generation of various active substances in local high-concentration regions; at the same time, the microdroplet acceleration effect can enhance the oxidation activity of substances such as hydroxyl radicals, water dimer radical cations, etc., thereby forming polyhydroxylated reserpine derivatives.

[0095] Example 5

[0096] use Figure 1 The apparatus shown was coupled with a mass spectrometer (LCQ Fleet mass spectrometer) to analyze fragment ions of five amino acids and plot quantitative curves at concentrations of 1, 10, 100, 500, and 1000 ng / mL. The specific operation is as follows:

[0097] The mass spectrometer was used in full scan mode with the following parameters: scan range 50–1000 Da, capillary voltage 25 V, capillary temperature 275 °C, lens voltage 75 V, and sheath gas flow rate, auxiliary gas flow rate, and purge gas flow rate all 0. Under the experimental conditions, each scan lasted 30 ms.

[0098] Using a single-tube structure, an amino acid mixture solution (containing five solutes: proline, valine, isoleucine, histidine, and phenylalanine, with a solvent volume ratio of 2 / 3 methanol / water) is drawn into a quartz capillary with an inner diameter of 40 μm through capillary action. The quartz capillary is then threaded through a 12-turn metal coil made of copper wire with a diameter of 0.3 mm and placed on a 3D moving platform.

[0099] Five amino acid mixtures were aspirated into a quartz capillary tube for detection. In the first amino acid mixture, the concentrations of proline, valine, isoleucine, histidine, and phenylalanine were all 1 ng / mL. In the second amino acid mixture, the concentrations of proline, valine, isoleucine, histidine, and phenylalanine were all 10 ng / mL. In the third amino acid mixture, the concentrations of proline, valine, isoleucine, histidine, and phenylalanine were all 100 ng / mL. In the fourth amino acid mixture, the concentrations of proline, valine, isoleucine, histidine, and phenylalanine were all 500 ng / mL. In the fifth amino acid mixture, the concentrations of proline, valine, isoleucine, histidine, and phenylalanine were all 1000 ng / mL.

[0100] Connect the positive lead to the rear end of the metal coil, and leave the negative lead 1.5cm away from the front end of the metal coil;

[0101] The DC arc generator is started, and the daily 220V AC power is boosted to 17kV through a small circuit board, which generates an arc discharge at the front end of the negative conductor and the metal coil, producing abundant plasma.

[0102] Figure 7 The quantitative curves for the five amino acids plotted in Example 5 are shown, with amino acid concentration on the x-axis and amino acid fragment ion signal intensity on the x-axis. This invention demonstrates good quantitative efficacy for the five amino acids. 2 All values ​​are greater than 0.99. This indicates that the pulsed DC arc-induced nano-liter electrospray ionization source with controllable in-source pyrolysis described in this invention has good stability.

[0103] The above embodiments demonstrate that the source-controlled pulsed DC arc-induced nanoliter electrospray ionization source of the present invention is an ion source with adjustable soft / hard ionization. Under low voltage conditions, it can maintain the integrity of molecular ions; under high voltage conditions, it can significantly enhance the intensity of characteristic fragment ions, thereby achieving accurate resolution of molecular structures. The present invention can effectively enhance the concentration of hydroxyl radicals and water dimer radical cations, accelerating their oxidation reactions and achieving the generation of polyhydroxyl oxidized drug molecules. Furthermore, the present invention exhibits excellent ionization performance, enabling efficient analysis of compounds with a wide polarity range; it also demonstrates excellent signal stability, making it suitable for the quantitative analysis of molecules such as amino acids. Notably, the present invention combines soft and hard ionization functions, allowing for flexible adjustment according to different analytical needs, providing optional solutions for the detection of various substances, and exhibiting superior detection performance and reliability.

[0104] Finally, it is necessary to state that the above embodiments should not be construed as limiting the scope of application of the present invention. The scope of protection of the present invention is defined by the appended claims, and any modifications based on the claims of the present invention are within the scope of protection of the present invention.

Claims

1. A pulsed DC arc-induced nanoliter electrospray ionization source and mass spectrometry system with controllable in-source fragmentation, characterized in that, include: Mass spectrometry; A capillary tube (1) is installed at the inlet of the mass spectrometer; A metal coil (2) wound around the capillary tube (1); Positive electrode wire (4), the positive electrode wire (4) is directly connected to the end of the metal coil (2) away from the mass spectrometer; The negative electrode wire (5) is connected at an interval to the end of the metal coil (2) near the mass spectrometer. A DC arc generator (3) is connected to the positive conductor (4) and the negative conductor (5).

2. The system according to claim 1, characterized in that, The outlet of the capillary (1) faces the inlet of the mass spectrometer, and the two are flush. The distance between the outlet of the capillary (1) and the inlet of the mass spectrometer is 1 to 30 mm.

3. The system according to claim 2, characterized in that, The sample outlet of the capillary (1) is a tip, and the inner diameter of the tip is between 1 μm and 500 μm.

4. The system according to claim 1, characterized in that, The diameter of the metal wire in the metal coil (2) is 0.1 to 5 mm; the number of turns in the metal coil (2) is 2 to 200.

5. The system according to claim 1, characterized in that, The negative electrode wire (5) is connected to the end of the metal coil (2) near the mass spectrometer at a distance of 0.1 to 5 cm.

6. The system according to claim 1, characterized in that, There may be one or more capillaries (1). When there are multiple capillaries (1), each capillary (1) adopts an array structure.

7. The system according to claim 1, characterized in that, A coaxial inner tube is provided inside the capillary (1), and the sample outlet of the inner tube is flush with the sample outlet of the capillary (1).

8. A detection method using the system described in any one of claims 1 to 7, characterized in that, Includes the following steps: a) The solution to be tested is drawn into the capillary tube (1); b) Start the DC arc generator (3) to boost the daily 220V AC power to 1~100kV. An arc discharge occurs in the gap between the negative electrode wire (5) and the metal coil (2) to generate plasma, which causes the solution to be detected to generate charged ions. At the same time, the potential difference generated by the metal coil (2) promotes the directional movement of charged ions. After the ions accumulate at the tip of the capillary (1), electrospray is generated and enters the mass spectrometer to complete the detection.

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