A microporous vibrating atomizing ionization device

Abstract

This invention relates to the field of electrospray ionization technology, providing a microporous vibratory nebulization ionization device, including a sample cell and a nebulizer. The nebulizer comprises a metal vibrator, an insulating layer, and a piezoelectric ceramic plate. The metal vibrator is in contact with the analyte in the sample cell. The metal vibrator has a cap-shaped structure with a central protrusion facing the insulating layer. The protrusion has a micron-sized single pore. The piezoelectric ceramic plate is connected to the positive and negative terminals of a power supply, respectively, allowing it to vibrate and thus drive the metal vibrator to vibrate. This ionization device offers advantages such as ultra-portability, low energy consumption, and wide applicability. It achieves strong ionization capability with a low voltage of 3-5V, making it widely applicable to the analysis of complex samples and proteins. As a soft ionization device, it can largely preserve the molecular structure of the analyte. Furthermore, this device has the potential to be used in portable mass spectrometers for mobile, in-situ outdoor analysis.

Description

Technical Field

[0001] This invention relates to the field of electrospray ionization technology, and more particularly to a microporous vibration atomization ionization device. Background Technology

[0002] A mass spectrometer mainly consists of several major parts, including a sample introduction system, an ion source, a mass analyzer, a detector, and a data processing system. The ion source is considered the "heart" of the mass spectrometer because analyte molecules must be ionized to form an ion beam of a certain energy before they can be detected by the mass spectrometer. The most commonly used ion sources include electron impact ionization (EI), chemical ionization (CI), electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), and matrix-assisted laser desorption / ionization (MALDI). "Soft ionization" techniques, primarily ESI, play an important role in the direct mass spectrometry analysis of complex samples because they do not produce excessive fragment ions and can be analyzed under normal pressure. The main principle of ESI is that an external gas flow (such as nitrogen) and high voltage charge the liquid surface, creating atomization at the nozzle tip. As the solvent evaporates and the electric field reaches a certain strength, the ions are converted into gaseous ions, which then enter the mass spectrometer detector for detection.

[0003] Electrospray ionization (ESI) is a newly developed soft ionization technique for generating gaseous ions in recent years. The process involves the analyte entering the spray chamber via an nebulizer. Under a strong voltage, the sample solution is pulled out and broken into charged droplets. Drying gas continuously evaporates the solvent, reducing the droplet diameter. When the Rayleigh limit is reached, a Coulomb explosion occurs, producing even smaller charged droplets. When the electric field on the droplet surface reaches a certain intensity, bare ions are emitted from the droplet surface, transforming into gaseous ions, which are then detected by a mass spectrometer. Depending on the various forms of actual samples and the characteristics of different analytes, many different types of electrospray devices have emerged, such as electrospray desorption ionization (DESI), probe electrospray ionization (PESI), and electrospray extraction ionization (EESI). Different types of electrospray ionization devices have different analytical characteristics. Electrospray desorption ionization (DESI) is characterized by fast analysis speed, high specificity, and high sensitivity; probe electrospray ionization (PESI) is characterized by low sample consumption and strong salt resistance; and electrospray extraction ionization (EESI) is characterized by the fact that the sample does not come into direct contact with high voltage during the analysis process.

[0004] However, these electrospray devices all require a stable carrier gas (argon, nitrogen, etc.) and a high voltage to form an charged spray, allowing for better detection of the analyte. Relatively speaking, they are neither portable nor economical or environmentally friendly. While nanoliter electrospray ionization can generate a spray without an auxiliary gas, its extremely small nozzle diameter limits its application. It is generally only suitable for solution samples, and can easily cause nozzle tip clogging when analyzing complex samples. It is also unsuitable for viscous liquids or emulsions. Therefore, it is necessary to develop an electrospray ionization device that does not require a carrier gas or a high ionization voltage. Summary of the Invention

[0005] The present invention aims to overcome at least one of the shortcomings and deficiencies of the prior art mentioned above, and to provide a microporous vibration atomizing ionization device. This invention achieves its objective based on the following technical solution:

[0006] This invention provides a microporous vibration atomization ionization device, comprising a sample cell and an atomizing plate. The sample cell is used to hold the analyte, and the atomizing plate is used to ionize and spray the analyte. The atomizing plate includes a metal vibrating plate, an insulating layer, and a piezoelectric ceramic plate. The insulating layer is disposed between the metal vibrating plate and the piezoelectric ceramic plate to insulate them from each other. The metal vibrating plate is in contact with the analyte in the sample cell. The metal vibrating plate has a cap-shaped structure with a protrusion at its center. The protrusion has a single hole with a diameter on the micrometer scale, and the protrusion faces the insulating layer. The front and back sides of the piezoelectric ceramic plate are connected to the positive and negative terminals of a power supply, respectively, which can cause the piezoelectric ceramic plate to vibrate, thereby driving the metal vibrating plate to vibrate. The center of the metal vibrating plate and the insulating layer has a hole for spray to pass through.

[0007] Preferably, it also includes a protective cover for stabilizing the spray, one side of which is close to the piezoelectric ceramic plate and the opposite side corresponds to the sample inlet of the mass spectrometer.

[0008] Preferably, the atomizing plate is fixed to the sample cell by a fixing ring.

[0009] Preferably, the outer diameter of the piezoelectric ceramic sheet is 10-20 mm and the inner diameter is 2-6 mm.

[0010] Preferably, the outer diameter of the insulating layer is 10-20 mm and the inner diameter is 2-6 mm.

[0011] Preferably, the outer diameter of the metal vibrating plate is 10-20 mm and the inner diameter is 2-6 mm.

[0012] Preferably, the diameter of the single hole is 1 to 30 μm.

[0013] Preferably, the vibration frequency of the piezoelectric ceramic sheet is 100–200 kHz.

[0014] Preferably, the metal vibrating plate is made of steel.

[0015] Preferably, the insulating layer is made of a two-component epoxy structural adhesive.

[0016] Preferably, the voltage of the power supply connected to the piezoelectric ceramic sheet is 3 to 5V.

[0017] Preferably, the metal vibrating plate is further provided with a metal wire, which is used to selectively connect to a high voltage.

[0018] Preferably, the analyte includes a solution, a viscous liquid, or an emulsion.

[0019] Compared with traditional electrospray ionization methods, this invention employs different atomization and charging methods, which can achieve at least one of the following beneficial effects:

[0020] 1) It has the advantages of being portable (small size), environmentally friendly, low energy consumption (3-5V power supply and no auxiliary gas required) and having high ionization efficiency (higher than common electrospray ionization sources);

[0021] 2) Since the principle of this device is to atomize and charge the solution to be tested by high-frequency vibration, it has the characteristics of soft ionization and is suitable for direct analysis of complex samples at the molecular level.

[0022] 3) This device modifies the traditional atomizing plate by using the vibration of a piezoelectric ceramic plate to drive the vibration of a metal vibrating plate, thereby causing the analyte to be atomized through a small hole on the metal vibrating plate. On the one hand, by drilling only a single hole of a few micrometers on the metal vibrating plate, the analyte can be atomized into extremely small droplets. On the other hand, insulation is provided between the metal vibrating plate and the piezoelectric ceramic plate, which can avoid the influence of the voltage applied to the piezoelectric ceramic plate on the analyte. Moreover, a high voltage can be applied to the metal vibrating plate, thereby charging the solution in contact with the metal vibrating plate and further improving the signal response intensity.

[0023] 4) This device generates spray based on high-frequency vibration, thus it has the advantage of being less prone to clogging. It can even atomize emulsions and even certain viscous liquids, such as milk and essential oils, making it widely applicable. Aqueous samples can also be atomized efficiently without the need for organic solvents.

[0024] 5) Unlike traditional methods that apply high voltage to charge droplets, this invention features soft ionization, which can largely preserve the molecular structure of the analyte.

[0025] 6) This device can potentially be adapted to portable mass spectrometers for mobile, in-situ outdoor analysis. Attached Figure Description

[0026] Figure 1This is a schematic diagram of the structure of a microporous vibration atomizing ionization device according to a preferred embodiment of the present invention;

[0027] Figure 2 This is a schematic diagram of the structure of the atomizing plate according to a preferred embodiment of the present invention;

[0028] Figure 3 Comparison of mass spectrometry signals of vitamin B aqueous solution (1.0 μg / mL) in positive ion mode: (a) primary mass spectrum of electrospray mass spectrometry; (b) primary mass spectrum of the device of the present invention; (c) secondary mass spectrum of vitamin B (m / z 265);

[0029] Figure 4 Analysis of melamine in milk samples using the apparatus of the present invention in positive ion mode: (a) primary spectrum of milk sample; (b) secondary spectrum of melamine in milk sample;

[0030] Explanation of reference numerals in the attached drawings: Sample cell 1, Atomizing plate 2, Protective cover 3, Metal vibrating plate 4, Insulating layer 5, Piezoelectric ceramic plate 6, Protrusion 7, Single hole 8, Fixing ring 9, Hole 10, Metal wire 11, Analyte 12, Sample inlet 13. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] Example 1

[0033] like Figures 1-2 As shown, a preferred embodiment of the present invention provides a microporous vibration atomization ionization device, comprising a sample cell 1 and an atomizing plate 2 connected in sequence, wherein:

[0034] The sample cell 1 is used to hold the analyte, and the atomizing plate 2 is used to ionize and spray the analyte. The atomizing plate 2 includes a metal vibrating plate 4, an insulating layer 5, and a piezoelectric ceramic plate 6. The insulating layer 5 is disposed between the metal vibrating plate 4 and the piezoelectric ceramic plate 6 to insulate between them. The voltage applied to the piezoelectric ceramic plate 6 has pulse characteristics, which is not conducive to the ionization of the analyte. The insulating layer 5 is provided between the metal vibrating plate 4 and the piezoelectric ceramic plate 6 for insulation and isolation, which can avoid the influence of the voltage applied to the piezoelectric ceramic plate 6 on the analyte. The metal vibrating plate 4 is in contact with the analyte placed in the sample cell 1. The metal vibrating plate 4 has a cap-shaped structure with a protrusion 7 at its center, facing the insulating layer 5. The top of the protrusion 7 has a single hole 8 with a diameter in the micrometer range, approximately 1–30 μm, preferably 5–10 μm. The piezoelectric ceramic plate 6 is connected to the positive and negative terminals of the power supply on its front and back sides, respectively, allowing it to vibrate, which in turn drives the metal vibrating plate 4 to vibrate. The piezoelectric ceramic plate 6 and the insulating layer 5 have a hole 10 at their center for the spray to pass through. The outer diameter of the metal vibrating plate 4, the insulating layer 5, and the piezoelectric ceramic plate 6 is 10–20 mm, and the inner diameter is 2–6 mm (i.e., the diameter of the hole 10 and the diameter of the bottom of the protrusion 7), preferably 16 mm and 4 mm. After the power is turned on, the vibration of the piezoelectric ceramic plate 6 drives the vibration of the metal vibrating plate 4, causing the analyte in contact with the metal vibrating plate 4 to be broken up by high frequency, generating a spray and carrying energy, which then enters the mass spectrometer for analysis and detection.

[0035] Compared to traditional electrospray ionization, this invention employs a different atomization and charging method. A piezoelectric ceramic plate vibrates, driving a metal vibrator to vibrate, thus atomizing the analyte through small holes in the metal vibrator. This invention boasts strong atomization capabilities, requiring no carrier gas or organic solvents. Furthermore, it features low power consumption, requiring only two dry-cell batteries; its small size and portability, along with the ability to achieve or even surpass the effects of traditional electrospray ionization without applying high voltage, make it suitable for direct analysis of complex samples at the molecular level. Moreover, this invention utilizes high-frequency vibration to charge the spray, unlike the traditional method of applying high voltage to charge droplets, thus exhibiting soft ionization characteristics. This greatly preserves the molecular structure of the analyte, making it suitable for direct analysis of complex samples at the molecular level. It is also less prone to clogging and has a wide range of applications (it can analyze complex samples such as milk and essential oils).

[0036] The metal vibrating plate 4 is made of a thin, inert metal sheet with good toughness and high strength, such as steel. The insulating layer 5 is made of a two-component epoxy structural adhesive, which has the advantages of high temperature resistance, high strength, excellent insulation performance, and long service life. The piezoelectric ceramic plate 6 vibrates at a frequency of 100–200 kHz, generating spray based on high-frequency vibration, resulting in strong atomization capability. The piezoelectric ceramic plate 6 is powered by a 3–5V power supply, such as two dry batteries or 3–5V DC power, featuring low power consumption.

[0037] In this embodiment, the ionization device further includes a protective cover 3 for stabilizing the spray. One side of the protective cover 3 is close to the piezoelectric ceramic plate 6, and the opposite side corresponds to the sample inlet of the mass spectrometer. The protective cover stabilizes the spray, thereby reducing interference with the mass spectrometry response and improving signal stability. The atomizing plate 2 is fixed between the sample cell 1 and the protective cover 3 by a fixing ring 9.

[0038] In this embodiment, the metal vibrating plate 4 is also provided with a metal wire 11, which is used to selectively connect to a high voltage. A metal wire is pre-existing on the metal vibrating plate, which can selectively apply a high voltage, thereby charging the solution in contact with the metal vibrating plate and further improving the signal response intensity.

[0039] In this embodiment, the analyte includes a solution, a viscous liquid, or an emulsion. The ionization device of the present invention generates a spray based on high-frequency vibration, thus having the advantage of being less prone to clogging. It can even atomize emulsions or liquids of a certain viscosity, such as milk and essential oils; aqueous samples can also be efficiently atomized without the need for organic solvents.

[0040] The ionization device of the present invention has the advantages of being portable, environmentally friendly, low energy consumption, strong atomization ability and high ionization efficiency. It does not require carrier gas assistance or organic solvents, and also has the characteristics of soft ionization. It is suitable for direct analysis of complex samples at the molecular level, is not easy to clog, and has a wide range of applications.

[0041] Example 2

[0042] The application of this invention will be explained in detail below with reference to specific test samples.

[0043] 1. Mass spectrometry analysis of an aqueous solution of vitamin B (1.0 μg / mL) was performed using the apparatus of the present invention. The results are shown in [Figure number missing]. Figure 3 .

[0044] contrast Figure 3 As shown in (a) and (c), the mass spectrum peaks of the ions obtained by ionization in this invention perfectly match those of vitamin B molecules. (Comparison) Figure 3 As shown in (a) and (b), compared with conventional ESI, the ionization device of this invention produces a stronger mass spectrometry signal (mass spectrometry signal intensity of 8.41E5 in (a) and 7.69E6 in (b)), and requires no carrier gas or high voltage. Furthermore, the first-order spectra also show that the signal intensities of the fragment peaks m / z 122 and m / z 144 generated by the molecular ion peak m / z 265 in this invention are significantly lower than those generated by ESI, indicating that this invention can better preserve the molecular structure of the analyte and is a "softer" ionization device than ESI.

[0045] 2. Analysis of milk samples

[0046] Figure 4 These are the primary and secondary mass spectra of the analytical results of melamine in milk samples obtained in this invention. The experiment involved first adding melamine to pure milk to a concentration of 50 mg / L, then diluting the milk sample 50-fold before analysis. In positive ion mode, the signal for melamine is [M+H]. + (m / z=127)( Figure 4 (a) CID analysis of the signal reveals that m / z 127 produces three fragment peaks at m / z 60, 85, and 110, with m / z 85 being the dominant fragment peak. Figure 4 (b) This further confirms the molecular structure of melamine in the milk sample. This demonstrates that the present invention can directly analyze complex and viscous samples, solving the problem of easy clogging in existing electrospray ionization devices.

[0047] The ionization device of this invention has the advantages of being ultra-portable, low-power, and widely applicable. It achieves strong ionization capability with a low voltage of 3-5V, making it suitable for the analysis of complex samples and proteins. As a soft ionization device, this invention can preserve the molecular structure of the analyte to a great extent. Furthermore, this device has the potential to be applied to portable mass spectrometers for mobile, in-situ outdoor analysis.

[0048] Finally, it should be noted that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A microporous vibration atomizing ionization device, characterized in that, The device includes a sample cell (1) and an atomizing plate (2) connected in sequence. The sample cell (1) is used to hold the analyte, and the atomizing plate (2) is used to ionize and spray the analyte. The atomizing plate (2) includes a metal vibrating plate (4), an insulating layer (5), and a piezoelectric ceramic plate (6). The insulating layer (5) is disposed between the metal vibrating plate (4) and the piezoelectric ceramic plate (6) to insulate between them. The metal vibrating plate (4) is connected to the analyte in the sample cell (1). When the object is in contact, the metal vibrating plate (4) has a cap-shaped structure with a protrusion (7) at its center. The protrusion (7) has a single hole (8) with a diameter of micrometers. The protrusion (7) faces the insulating layer (5). The piezoelectric ceramic plate (6) is connected to the positive and negative terminals of the power supply on its front and back sides, respectively. The piezoelectric ceramic plate (6) can vibrate, thereby driving the metal vibrating plate (4) to vibrate. The piezoelectric ceramic plate (6) and the insulating layer (5) have a hole (10) at their center for spray to pass through. The metal vibrating plate (4) is also provided with a metal wire (11), which is used to selectively connect to a high voltage.

2. The microporous vibration atomizing ionization device according to claim 1, characterized in that, It also includes a protective cover (3) for stabilizing the spray, one side of which is close to the piezoelectric ceramic plate (6) and the opposite side corresponds to the inlet of the mass spectrometer.

3. The microporous vibration atomizing ionization device according to claim 1, characterized in that, The atomizing plate (2) is fixed to the sample cell (1) by a fixing ring (9).

4. The microporous vibration atomizing ionization device according to claim 1, characterized in that, The outer diameter of the insulating layer (5) and / or the piezoelectric ceramic sheet (6) is 10-20 mm and the inner diameter is 2-6 mm, and / or the outer diameter of the metal vibrating sheet (4) is 10-20 mm and the inner diameter is 2-6 mm.

5. The microporous vibration atomizing ionization device according to claim 1, characterized in that, The diameter of the single hole (8) is 1 to 30 μm.

6. The microporous vibration atomizing ionization device according to claim 1, characterized in that, The vibration frequency of the piezoelectric ceramic sheet (6) is 100-200 kHz.

7. The microporous vibration atomizing ionization device according to claim 1, characterized in that, The metal vibrating plate (4) is made of steel, and / or the insulating layer (5) is made of two-component epoxy structural adhesive.

8. The microporous vibration atomizing ionization device according to claim 1, characterized in that, The voltage of the power supply connected to the piezoelectric ceramic sheet (6) is 3 to 5V.

9. The microporous vibration atomizing ionization device according to claim 1, characterized in that, The analyte includes solutions, viscous liquids, or emulsions.

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