Laser-based metal film vibration mass spectrum sampling method

Abstract

The invention belongs to the technical field of mass spectrometry analysis and research, and discloses a laser-based metal film vibration mass spectrometry sampling method which comprises the following specific steps: step 1, dissolving a to-be-detected sample to prepare a saturated solution of melamine, taking ethanol as a solvent, and oscillating the prepared solution by using an ultrasonic oscillator to ensure that the solution is in a uniform dispersion state; a sample is uniformly sprayed on titanium foil, a laser thermal mechanical effect is accurately regulated and controlled, non-contact desorption is realized by utilizing mechanical vibration wave conduction with optimized thickness of the titanium foil, the problem of molecular cracking caused by direct irradiation of traditional laser is effectively avoided, a uniform sample layer is formed through ultrasonic dispersion pretreatment and warm lamp temperature control drying, and the thermal mechanical effect of the titanium foil is accurately regulated and controlled. Dynamic sampling of a three-position translation table and laser parameter adaptation are combined, meanwhile, a cooperative adjustment mechanism of thermal expansion response of a titanium foil substrate and the distance of an ion source can be compatible with diversified sample analysis, and stable and repeatable long-time mass spectrum detection is achieved on the premise that the integrity of a molecular structure is maintained.

Description

Technical Field

[0001] The present invention belongs to the technical field of mass spectrometry research, and specifically relates to a laser-based vibration mass spectrometry sampling method for metal thin films. Background Technique

[0002] Mass spectrometry is an analytical technique based on the separation and detection of substances according to the differences in mass-to-charge ratio (m / z), and is widely used in the fields of chemistry, biology, medicine, environmental science, and materials science.

[0003] Desorbing non-volatile organic molecule from the substrate requires sufficient energy to break the "bonds" between the sample molecules and the substrate. The common method based on directly focusing the laser beam on the desorption of sample molecules will inevitably increase the internal energy of the molecules, resulting in the breaking of some chemical bonds within the molecules. A large number of fragment ion peaks will appear in the mass spectrometry detection, making it difficult to obtain the parent ion peak. With the rapid development of biomedicine, the demand for measuring the molecular weights of macromolecular compounds is increasing. Mass spectrometry urgently needs to develop a "soft desorption" method to detect organic molecules and obtain the complete molecular ion signal of the sample molecules. Therefore, it needs to be improved. Summary of the Invention

[0004] The purpose of the present invention is to provide a laser-based vibration mass spectrometry sampling method for metal thin films to solve the problems raised in the above background technique.

[0005] To achieve the above purpose, the present invention provides the following technical solution: A laser-based vibration mass spectrometry sampling method for metal thin films, and the specific steps are as follows:

[0006] Step 1: Dissolve the sample to be measured

[0007] Prepare a saturated solution of melamine with ethanol as the solvent, and use an ultrasonic oscillator to oscillate the prepared solution to ensure its uniform dispersion state;

[0008] Step 2: Spray the sample

[0009] Spray the sample evenly onto the titanium foil;

[0010] Step 3: Dry the sample

[0011] Dry the sample in Step 2 with a warm lamp, leaving a thin and uniform sample;

[0012] Step 4: Fix the sample

[0013] Fix the titanium foil on a three-axis moving platform with a bracket, and keep the thin film flat and taut;

[0014] Step 5: Inject the sample

[0015] Place the sample at an appropriate position from the sampling end of the ion source;

[0016] Step Six: Trigger the laser

[0017] Turn on the desorption laser, focus it onto the titanium foil through a focusing lens, and the sample attached to the back of the titanium foil can be desorbed from the titanium foil;

[0018] Step Seven: Start the injection platform

[0019] At the same time, turn on the motor of the moving platform. Driven by the motor, the sample moves continuously to ensure that the desorption laser does not only irradiate the same point on the titanium foil;

[0020] Step Eight: Turn on the ionization source

[0021] Turn on the dielectric barrier discharge ionization source to ionize the sample desorbed by the desorption laser, and the ionized ions are detected by the mass spectrometry detector.

[0022] Preferably, in Step One, the ultrasonic oscillator oscillates the configured solution for 3 minutes to ensure that the solution is evenly dispersed without aggregation.

[0023] Preferably, the thickness of the titanium foil in Step Two is 8 - 14 microns.

[0024] Preferably, the specific numerical values of the length and width dimensions of the titanium foil in Step Two are determined according to the size of the fixed bracket.

[0025] Preferably, the laser irradiation site in Step Six is the side of the titanium foil without the sprayed sample.

[0026] Preferably, when the laser in Step Six irradiates the titanium foil, the part of the titanium foil irradiated by the focused laser will rapidly heat up and undergo thermal expansion, thereby causing mechanical vibration of the titanium foil. When the mechanical wave propagates to the sample on the other side of the titanium foil, the sample on the back of the titanium foil will be desorbed from the titanium foil.

[0027] Preferably, the specific values of the laser in Step Six are: wavelength is 532 nanometers, and pulse frequency is 10 hertz.

[0028] Preferably, the distance between the metal film and the ion source and the intensity of the laser in Step Five need to be adjusted according to the physical and chemical components of the sample to obtain the best mass spectrometry signal.

[0029] Preferably, in Step Three, a warm lamp is used to dry the sample solution, and the drying time should be controlled within 5 minutes.

[0030] The beneficial effects of the present invention are as follows:

[0031] By uniformly spraying the sample on the titanium foil and precisely controlling the laser thermo-mechanical effect, non-contact desorption is achieved by utilizing the optimized mechanical vibration wave conduction of the titanium foil thickness, effectively avoiding the problem of molecular cleavage caused by traditional direct laser irradiation. A uniform sample layer is formed through ultrasonic dispersion pretreatment and warm lamp temperature-controlled drying. Combining three-dimensional translation stage dynamic sampling and laser parameter adaptation, at the same time, the synergistic adjustment mechanism of the thermal expansion response of the titanium foil substrate and the ion source distance can be compatible with diverse sample analysis, realizing stable and reproducible long-term mass spectrometry detection while maintaining the integrity of the molecular structure, especially suitable for the precise mass spectrometry characterization of fragile biological macromolecules and complex organic compounds. Description of the Drawings

[0032] Figure 1 It is the schematic diagram of the mass spectrometry sampling and detection of non-volatile organic compounds in the present invention;

[0033] Figure 2 It is the morphology diagram after the direct action of the laser on the titanium foil on the side facing the laser (a) and the morphology diagram of the back surface of the titanium foil, that is, the sample surface (b) after the laser action in the present invention;

[0034] Figure 3 It is the influence diagram of the distance between the titanium foil and the sampling inlet of the ion source and the laser power density on the mass spectrometry signal intensity in the second embodiment of the present invention;

[0035] Figure 4 It is the mass spectrometry diagram of melamine in the second embodiment of the present invention. Detailed Embodiments

[0036] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0037] Embodiment 1

[0038] As Figures 1 to 2 shown, the embodiment of the present invention provides a laser-based metal thin film vibration mass spectrometry sampling method, and the specific steps are as follows:

[0039] Step 1: Dissolution of the sample to be measured

[0040] Prepare a saturated solution of melamine, with ethanol as the solvent, and use an ultrasonic oscillator to oscillate the prepared solution to ensure its uniformly dispersed state;

[0041] Step 2: Sample spraying

[0042] Spray the sample uniformly onto the titanium foil;

[0043] Step 3: Drying the sample

[0044] Dry the sample from Step 2 with a warm lamp, leaving a thin and uniform layer of the sample;

[0045] Step 4: Fixing the sample

[0046] Fix the titanium foil on the three-axis moving platform with a bracket, and keep the thin film flat and taut;

[0047] Step 5: Loading the sample

[0048] Place the sample at an appropriate position from the sampling end of the ion source;

[0049] Step 6: Triggering the laser

[0050] Turn on the desorption laser, focus it onto the titanium foil through a focusing lens, and the sample attached to the back of the titanium foil can be desorbed from the titanium foil;

[0051] Step 7: Starting the sample loading platform

[0052] At the same time, turn on the motor of the moving platform. Driven by the motor, the sample moves continuously to ensure that the desorption laser does not irradiate the same point on the titanium foil;

[0053] Step 8: Turning on the ionization source

[0054] Turn on the dielectric barrier discharge ionization source to ionize the sample desorbed by the desorption laser, and the ionized ions are detected by the mass spectrometry detector.

[0055] First, dissolve or make the sample to be measured into a suspension, evenly spray it on the titanium foil. After the sample is dried, send the sample into the mass spectrometer for detection. At the same time, turn on the motor of the moving platform to make the laser irradiate different points on the titanium foil, and long-term sampling analysis can be carried out. The experimental results show that this new laser-based mass spectrometry sampling method is suitable for mass spectrometry analysis of non-volatile organic molecules. Compared with the traditional laser-based mass spectrometry sampling method, this method has the advantage of avoiding a large number of fragments generated by molecular cleavage.

[0056] Among them, in Step 1, the ultrasonic oscillator oscillates the prepared solution for 3 minutes to ensure that the solution is evenly dispersed without aggregation.

[0057] The ultrasonic oscillator oscillates the solution for 3 minutes to ensure that the sample is evenly dispersed and eliminate the aggregation phenomenon in the solution. This pretreatment improves the uniformity of the sample distribution sprayed on the titanium foil, avoids the interference of local high concentration or agglomeration on the subsequent mass spectrometry detection, and thus enhances the repeatability and accuracy of the experimental data.

[0058] Among them, in Step 2, the thickness of the titanium foil is 8 - 14 microns.

[0059] Select a titanium foil with a thickness of 8 - 14 microns as the substrate. This thickness range can balance mechanical strength and thermal response characteristics. A thinner titanium foil can generate effective thermal expansion vibration waves, while sufficient thickness can prevent laser penetration damage, enabling the mechanical wave to conduct to the sample surface with just the right amount of energy to reach the desorption threshold, avoiding molecular cleavage while ensuring desorption efficiency.

[0060] Among them, the specific numerical values of the length and width dimensions of the titanium foil in step two are determined according to the size of the fixed bracket.

[0061] The size of the titanium foil is customized according to the bracket to ensure a perfect fit with the three - axis moving platform. This customized design keeps the titanium foil in a uniformly taut state after fixation, which is beneficial to the directional conduction of mechanical vibration waves.

[0062] Among them, the laser irradiation site in step six is the side of the titanium foil without the sprayed sample.

[0063] The laser irradiates the side of the titanium foil without the sample, indirectly driving the desorption of the sample through the thermal expansion effect. This non - contact energy transfer method avoids direct laser irradiation of the sample molecules, significantly reducing the risk of chemical bond breakage caused by the photothermal effect.

[0064] Among them, when the laser irradiates the titanium foil in step six, the part of the titanium foil irradiated by the focused laser will rapidly heat up and undergo thermal expansion, thereby causing the titanium foil to generate mechanical vibration. When the mechanical wave conducts to the sample on the other side of the titanium foil, the sample on the back of the titanium foil will be desorbed from the titanium foil.

[0065] The laser - induced mechanical vibration wave conduction mechanism utilizes the instantaneous thermal expansion of the titanium foil to generate stress waves. This physical action mode precisely transfers energy to the sample interface in the form of mechanical waves, maintaining the integrity of the molecular structure during desorption and effectively solving the problem of fragment peak interference.

[0066] Among them, the specific values of the laser in step six are: the wavelength is 532 nanometers, and the pulse frequency is 10 hertz.

[0067] By adopting the laser parameter combination of a 532nm wavelength and a 10Hz pulse frequency, it not only ensures sufficient vibration energy but also avoids overheating and deformation of the substrate.

[0068] Among them, the distance between the metal thin film and the ion source and the intensity of the laser in step five need to be adjusted according to the physical and chemical composition of the sample to obtain the best mass spectrometry signal.

[0069] The optimized scheme of dynamically adjusting the distance between the thin film and the ion source and the laser intensity adapts the parameters according to the characteristics of different samples such as molecular weight and polarity, significantly improving the universality of the method and enabling the same platform to be compatible with the detection of diverse samples.

[0070] Among them, in Step 3, a warm lamp is used to dry the sample solution, and the drying time should be controlled within 5 minutes.

[0071] By precisely controlling the drying time, a uniform sample layer can be formed while preventing film cracking caused by over-drying.

[0072] Example 2

[0073] As Figures 1 to 4 shown, the embodiment of the present invention provides a laser-based vibration mass spectrometry sampling method for metal thin films, and the specific steps are as follows:

[0074] Step 1: Dissolution of the sample to be measured

[0075] Prepare a saturated solution of melamine with ethanol as the solvent, and use an ultrasonic oscillator to vibrate the prepared solution to ensure its uniform dispersion state;

[0076] Step 2: Sample spraying

[0077] Spray the sample evenly onto the titanium foil;

[0078] Step 3: Sample drying

[0079] Dry the sample in Step 2 with a warm lamp, leaving a thin and uniform sample layer;

[0080] Step 4: Sample fixation

[0081] Fix the titanium foil on a three-axis moving platform with a bracket, and keep the thin film flat and taut;

[0082] Step 5: Sampling

[0083] Place the sample at an appropriate position from the sampling end of the ion source;

[0084] Step 6: Trigger the laser

[0085] Turn on the desorption laser, and focus it on the titanium foil through a focusing lens, so that the sample attached to the back of the titanium foil can be desorbed from the titanium foil;

[0086] Step 7: Start the sampling platform

[0087] At the same time, turn on the motor of the moving platform. Driven by the motor, the sample is continuously moving to ensure that the desorption laser does not irradiate the same point on the titanium foil;

[0088] Step 8: Turn on the ionization source

[0089] Turn on the dielectric barrier discharge ionization source to ionize the sample desorbed by the desorption laser, and the ionized ions are detected by the mass spectrometry detector.

[0090] First, dissolve or suspend the sample to be tested, and evenly spray it on the titanium foil. After the sample is dried, send the sample into the mass spectrometer for detection. At the same time, turn on the motor of the mobile platform to make the laser irradiate different points on the titanium foil, and long-term sampling analysis can be carried out. The experimental results show that this new laser-based mass spectrometry sampling method is suitable for mass spectrometry analysis of non-volatile organic molecules. Compared with the traditional laser-based mass spectrometry sampling method, this method has the advantage of avoiding a large number of fragments generated by molecular cleavage, as shown in the attached Figure 4 As shown, curve 1 is the matrix mass spectrometry signal of melamine obtained under the combined action of the desorption laser and the ionization source; curve 2 is the mass spectrometry signal of the sample that does not appear when only the first desorption laser acts, indicating that under the action of the first laser, the non-volatile organic matter melamine is desorbed from the titanium foil, and its sampling and mass spectrometry analysis are successfully carried out.

[0091] Among them, in step one, the ultrasonic oscillator oscillates the prepared solution for 3 minutes to ensure that the solution is evenly dispersed without aggregation.

[0092] The ultrasonic oscillator oscillates the solution for 3 minutes to ensure that the sample is evenly dispersed and eliminates the aggregation phenomenon in the solution. This pretreatment improves the uniformity of the sample sprayed on the titanium foil and avoids the interference of local high concentration or caking on the subsequent mass spectrometry detection, thereby enhancing the repeatability and accuracy of the experimental data.

[0093] Among them, in step two, the thickness of the titanium foil is 8 - 14 microns.

[0094] Select a titanium foil with a thickness of 8 - 14 microns as the substrate. This thickness range can balance the mechanical strength and thermal response characteristics. A thinner titanium foil can generate effective thermal expansion vibration waves, while a sufficient thickness can prevent the laser from penetrating and damaging, so that the mechanical wave conduction to the sample surface just reaches the desorption threshold, avoiding molecular cleavage and ensuring the desorption efficiency.

[0095] Among them, in step two, the specific numerical values of the length and width dimensions of the titanium foil are determined according to the size of the fixed bracket.

[0096] The size of the titanium foil is customized according to the bracket to ensure a perfect fit with the three-dimensional mobile platform. This customized design keeps the titanium foil in a uniform and tight state after being fixed, which is beneficial to the directional conduction of mechanical vibration waves.

[0097] Among them, in step six, the laser irradiation site is the side of the titanium foil without the sprayed sample.

[0098] The laser irradiates the side of the titanium foil without the sample, and indirectly drives the desorption of the sample through the thermal expansion effect. This non-contact energy transfer avoids direct laser irradiation of the sample molecules and significantly reduces the risk of chemical bond breakage caused by the photothermal effect.

[0099] Among them, when the laser irradiates the titanium foil in step six, the part of the titanium foil irradiated by the laser focus will rapidly heat up and undergo thermal expansion, which will cause the titanium foil to generate mechanical vibration. When the mechanical wave propagates to the sample on the other side of the titanium foil, the sample on the back of the titanium foil will be desorbed from the titanium foil.

[0100] The conduction mechanism of the laser-induced mechanical vibration wave uses the instantaneous thermal expansion of the titanium foil to generate stress waves. This physical action mode accurately transfers energy to the sample interface in the form of mechanical waves, maintains the integrity of the molecular structure during desorption, and effectively solves the problem of fragment peak interference.

[0101] Among them, the specific values of the laser in step six are a wavelength of 532 nanometers and a pulse frequency of 10 hertz.

[0102] By adopting the laser parameter combination of a 532nm wavelength and a 10Hz pulse frequency, it not only ensures sufficient vibration energy but also avoids overheating and deformation of the substrate.

[0103] Among them, the distance between the metal film and the ion source and the intensity of the laser in step five need to be adjusted according to the physical and chemical composition of the sample to obtain the best mass spectrometry signal.

[0104] The optimization scheme of dynamically adjusting the distance between the film and the ion source and the laser intensity adapts the parameters according to the characteristics such as the molecular weight and polarity of different samples, significantly improving the universality of the method and making the same platform compatible with the detection of diverse samples.

[0105] Among them, in step three, a warm lamp is used to dry the sample solution, and the drying time should be controlled within 5 minutes.

[0106] By precisely controlling the drying time, not only a uniform sample layer can be formed, but also film cracking caused by over-drying can be prevented.

[0107] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device.

[0108] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A laser-based metal film vibration mass spectrometry sampling method, characterized in that: The specific steps are as follows: Step 1: Dissolve the sample to be tested A saturated solution of melamine is prepared, the solvent is ethanol, and the prepared solution is shaken with an ultrasonic oscillator to ensure that it is in a uniformly dispersed state; Step 2: Sample spraying The sample was sprayed evenly onto the titanium foil; Step 3: Sample drying Dry the sample in step 2 with a warm lamp, leaving a thin and uniform layer of the sample; Step 4: Sample Fixation Fix the titanium foil on a three-dimensional moving platform with a bracket, and keep the film flat and tight; Step 5: Sample injection Place the sample at a suitable distance from the sampling end of the ion source; Step 6: Trigger the laser Turn on the desorption laser and focus it onto the titanium foil through a focusing lens, so that the sample attached to the back of the titanium foil can be desorbed from the titanium foil; Step 7: Start the injection platform At the same time, the motor of the mobile platform is turned on. Driven by the motor, the sample is constantly moved to ensure that the desorption laser does not irradiate only the same point of the titanium foil. Step 8: Turn on the ionization source The dielectric barrier discharge ionization source is turned on to ionize the sample desorbed by the desorption laser, and the ionized ions are detected by the mass spectrometer detector.

2. The laser-based metal film vibration mass spectrometry sampling method according to claim 1, characterized in that: The ultrasonic oscillator described in step 1 oscillates the prepared solution for 3 minutes to ensure that the solution is evenly dispersed without aggregation.

3. The laser-based metal film vibration mass spectrometry sampling method according to claim 1, characterized in that: The thickness of the titanium foil in step 2 is 8 to 14 microns.

4. The laser-based metal film vibration mass spectrometry sampling method according to claim 1, characterized in that: The specific values ​​of the length and width of the titanium foil in step 2 are determined according to the fixed bracket size.

5. The laser-based metal film vibration mass spectrometry sampling method according to claim 1, characterized in that: The laser irradiation area in step six is ​​the side of the titanium foil that is not sprayed with the sample.

6. The laser-based metal film vibration mass spectrometry sampling method according to claim 1, characterized in that: When the laser irradiates the titanium foil in step six, the part of the titanium foil irradiated by the laser will heat up rapidly and expand thermally, which will cause mechanical vibration of the titanium foil. When the mechanical wave is transmitted to the sample on the other side of the titanium foil, the sample on the back of the titanium foil will be detached from the titanium foil.

7. The laser-based metal film vibration mass spectrometry sampling method according to claim 1, characterized in that: The specific values ​​of the laser in step six are: a wavelength of 532 nanometers and a pulse frequency of 10 Hz.

8. The laser-based metal film vibration mass spectrometry sampling method according to claim 1, characterized in that: The distance between the metal film and the ion source and the intensity of the laser in step 5 need to be adjusted according to the physical and chemical composition of the sample to obtain the best mass spectrometry signal.

9. The laser-based metal film vibration mass spectrometry sampling method according to claim 1, characterized in that: As described in step 3, use a warm lamp to dry the sample solution. The drying time should be controlled within 5 minutes.

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