Microwave-assisted laser double-beam ablation cell

Abstract

The present invention discloses a microwave-assisted laser double-beam ablation cell, which includes a sample cell, a focusing mirror, an ablation laser, and a microwave emitter. A laser lens is provided at the top of the sample cell. The laser emitted by the ablation laser sequentially passes through the focusing mirror and the laser lens and enters the sample cell. The microwave emitted by the microwave emitter enters the sample cell through the laser lens. After the sample is ablated by the ablation laser in the present invention, aerosol particles of different sizes are generated. Through the microwave emitted by the microwave emitter, the particle size of the aerosol particles becomes smaller, evaporates and finally atomizes, and the solvent in the aerosol particles is also removed, so that more solutes enter the inductively coupled plasma mass spectrometry for ionization analysis, thereby reducing the oxide interference in the detection process, improving the detection limit of elements, enhancing the sensitivity, stability and analysis performance of the instrument, and reducing the memory effect and plasma matrix effect of the instrument, and obtaining more real, accurate high-precision element content and isotope ratio.

Description

Technical Field

[0001] The present invention relates to the technical field of laser ablation, and in particular to a microwave-assisted laser double-beam ablation cell. Background Art

[0002] Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is the main analytical method for obtaining high-precision elements and isotopes of samples in different fields. The LA-ICP-MS technology has the analytical advantages of in-situ, real-time, fast, accurate, and non-destructive, as well as high sensitivity, good spatial resolution, multi-element determination, and the detection ability to provide isotope ratio information. This technology is widely used in the fields of geology, chemistry, materials science, environment, paleontology, etc.

[0003] Solution pneumatic nebulization injection is the most mainstream sample introduction system in modern ICP-MS. It converts the sample solution into extremely fine aerosol particles and continuously transports them into the plasma. However, the aerosol particle size distribution formed by the conventional nebulizer is relatively large, and only about 2-3% of the tiny aerosols are successfully introduced into ICP-MS, resulting in low efficiency of traditional nebulization injection, and a large amount of samples are discharged in the form of waste liquid. To solve the dilemma of traditional solution nebulization, different types of new solution nebulization methods have been proposed in recent years, such as ultrasonic nebulization technology or thermal nebulization technology. However, these technologies all have problems such as excessive solvent amount, aggravated ICP matrix effect and memory effect problems, and reduced instrument stability.

[0004] On the other hand, natural liquids are a major category in geological analysis, such as river water, seawater, groundwater, brine, petroleum, etc. Their elemental composition and isotope ratio information are of great significance in studying geological evolution processes, related mineral resource development, environmental pollution surveys, etc. Although liquid samples have better elemental distribution uniformity compared to solid samples, their complex composition makes it difficult for traditional nebulization techniques to directly introduce samples into ICP. For example, the ultra-high organic matter content of petroleum samples or the high salt content in brines easily lead to problems such as nebulizer blockage, cone hole blockage, and severe matrix effect during the ICP-MS test. Therefore, in actual tests, natural liquid samples still need to undergo complex pretreatment operations such as centrifugation, filtration, dilution or enrichment, and medium conversion.

[0005] Mass spectrometry interference and non-mass spectrometry interference are the two main factors affecting the quality of ICP-MS data analysis. Mass spectrometry interference comes from isotopes or polyatomic ions with the same mass-to-charge ratio as the element to be measured. Non-mass spectrometry interference is often referred to as the matrix effect, which is affected by the chemical composition and content of the sample. Usually, a large dilution method is used to reduce the influence of the matrix effect. In general geological sample analysis, the dilution factor is required to be greater than 2000. In ICP-MS analysis, the sample is usually introduced by solution nebulization (sample consumption is 0.1 - 1 mL / min). The continuously introduced aqueous solution is the main source of hydrogen and oxygen in the plasma, and the interference of the corresponding oxides and hydroxides of these two elements is one of the most difficult interference types to solve in traditional ICP-MS analysis. For example, when testing rare earth elements in geological samples, it will be affected by the oxide and hydroxide ion interference of Ba element, especially for samples with significantly higher Ba content than rare earth element content, such as the international geological standard sample GSP-2 (granodiorite); when the content of light rare earths in the sample is significantly higher than that of medium and heavy rare earths, the former will also have an obvious impact on the latter's test.

[0006] Currently, the membrane desolvation device is the most commonly used method for suppressing mass spectrometry interference caused by aqueous solutions. However, after connecting the membrane desolvation device, many serious disadvantages will also arise, such as the instrument's tolerance to the matrix becoming worse; the memory effect being significantly enhanced; when analyzing high-salt samples, it may cause membrane blockage, resulting in signal intensity suppression and an increase in oxide yield. In addition, the membrane desolvation injection method cannot solve the problem of non-mass spectrometry interference in inductively coupled plasma mass spectrometry. Summary of the Invention

[0007] The main object of the present invention is to propose a microwave-assisted laser double-beam ablation cell, which can make the aerosol particles of different sizes ablated smaller and more uniform through the action of microwaves, and can improve the detection sensitivity.

[0008] To achieve the above object, the present invention provides a microwave-assisted laser double-beam ablation cell, which includes a sample cell, a focusing mirror, an ablation laser, and a microwave emitter. The top of the sample cell is sealed by a laser lens; the focusing mirror is located outside the sample cell and is close to the laser lens; the laser emitted by the ablation laser passes through the focusing mirror and then enters the sample cell through the laser lens; the microwave emitted by the microwave emitter enters the sample cell through the laser lens.

[0009] Optionally, it further includes a shielding cover covering the outside of the sample cell, and an opening is provided at the top of the shielding cover; the focusing mirror, the ablation laser, and the microwave emitter are all located outside the shielding cover, and the laser emitted by the ablation laser enters the sample cell through the opening.

[0010] Optionally, the shielding cover is made of aluminum alloy material; and / or, the length of the shielding cover is 200 - 205 mm, the width is 150 - 155 mm, and the height is 50 - 55 mm; and / or, observation windows are provided on both the front and rear side walls of the shielding cover, and a high-density brass mesh is laid on each observation window.

[0011] Optionally, the microwave emitter includes an emission end. Among them, a limiting port is provided at the top of the shielding cover, and the emission end extends into the shielding cover through the limiting port; and / or, the distance between the emission end and the surface of the sample in the sample cell is 4 - 5 mm.

[0012] Optionally, a soft high-density wire mesh is laid in the limiting port, and the emission end is clamped in the soft high-density wire mesh.

[0013] Optionally, the microwave emitter includes a resonant cavity and a microwave source controller. The resonant cavity includes a first end and a second end. The first end is used to emit microwaves towards the sample cell; the microwave source controller is connected to the second end through a radio frequency line.

[0014] Optionally, the sample cell is connected to a carrier pipeline and an air outlet pipeline. Among them, the carrier pipeline is used to transport inert gas; and / or, the gas flow rate in the carrier pipeline is 650 - 655 mL / min.

[0015] Optionally, the microwave frequency emitted by the microwave emitter is 433 MHz, 915 MHz, 2.54 GHz or 5.80 GHz; and / or, the power of the microwave emitter is 10 - 200 W.

[0016] Optionally, the thickness of the laser lens is 0.4 - 1 mm; and / or, the transmittance of the 193 nm ultraviolet laser through the laser lens is not less than 92%; and / or, the laser beam spot diameter emitted by the ablation laser is 100 - 105 µm; and / or, the pulse frequency of the ablation laser is 5 - 10 Hz; and / or, the laser energy emitted by the ablation laser is 8 - 10 J·cm -2 。

[0017] Optionally, it further includes a total reflection mirror, which is arranged between the focusing mirror and the ablation laser, and is used to reflect the laser emitted by the ablation laser so that the laser shoots towards the focusing mirror.

[0018] In the technical solution of the present invention, when detecting a liquid sample, after the sample is ablated by the ablation laser, aerosol particles of different sizes are generated. The microwave emitted by the microwave emitter makes the particle size of the aerosol particles smaller, evaporates and finally atomizes. At the same time, the microwave can also remove the solvent in the aerosol particles, enabling more solutes to enter the inductively coupled plasma mass spectrometry for ionization analysis, thereby reducing the oxide interference during the detection process, improving the detection limit of elements, enhancing the sensitivity, stability and analysis performance of the instrument, and reducing the memory effect and plasma matrix effect of the instrument, so as to obtain more real, accurate high-precision element content and isotope ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0020] Figure 1 It is a schematic structural diagram of a microwave-assisted laser double-beam ablation cell provided by an embodiment of the present invention.

[0021] The reference numeral descriptions of the embodiments provided by the present invention are as follows:

[0022] Label Name Label Name 100 Microwave-assisted laser double-beam ablation cell 4 Shielding cover 1 Sample cell 41 Limit port 11 Sample groove 42 Observation window 2 Focusing mirror 5 Carrier pipeline 3 Microwave transmitter 6 Outlet pipeline 31 Resonant cavity 7 Total reflection mirror 32 Microwave source controller 8 Microwave beam 33 RF cable 9 Laser lens

[0023] The realization, functional characteristics and advantages of the object of the present invention will be further described in conjunction with the embodiments and with reference to the drawings. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0025] It should be noted that if there are directional indications (such as up, down, left, right, front, back...) involved in the embodiments of the present invention, the directional indications are only used to explain the relative positional relationship and movement conditions between components in a specific posture (as shown in the drawings). If the specific posture changes, the directional indications will also change accordingly.

[0026] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are for descriptive purposes only, and should not be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the meaning of "and / or" appearing throughout the text includes three parallel scenarios. Taking "A and / or B" as an example, it includes scenario A, or scenario B, or the scenario where both A and B are satisfied simultaneously. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or inability to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0027] Currently, the membrane desolvation device is the most commonly used method for suppressing mass spectrometry interference caused by aqueous solutions. However, after connecting the membrane desolvation device, many serious drawbacks will also occur. For example, the tolerance of the instrument to the matrix becomes worse; the memory effect is significantly enhanced; when analyzing high-salt samples, membrane clogging may occur, resulting in the suppression of signal intensity and an increase in the oxide yield. In addition, the membrane desolvation injection method cannot solve the problem of non-mass spectrometry interference in inductively coupled plasma mass spectrometry.

[0028] In view of this, the present invention provides a microwave-assisted laser double-beam ablation cell, which can make the aerosol particles of different sizes ablated smaller and more uniform through the action of microwaves, and can improve the detection sensitivity. Figure 1 It is a schematic structural diagram of the microwave-assisted laser double-beam ablation cell provided by an embodiment of the present invention.

[0029] In the technical solution of the present invention, the microwave-assisted laser double-beam ablation cell 100 includes a sample cell 1, a focusing mirror 2, an ablation laser, and a microwave emitter 3. The top of the sample cell 1 is sealed by a laser lens 9; the focusing mirror 2 is located outside the sample cell 1 and is disposed close to the laser lens 9; the laser emitted by the ablation laser passes through the focusing mirror 2 and then enters the sample cell 1 through the laser lens 9; the microwave emitted by the microwave emitter 3 enters the sample cell 1 through the laser lens 9.

[0030] In the above technical solution, the specific structure of the sample cell 1 is not limited, and it can be columnar, cubic, etc. The purpose is to hold the sample to be ablated. A laser lens 9 is provided on one side wall of the sample cell 1 for allowing the laser beam 8 to pass through. Preferably, the laser lens 9 is provided at the top of the sample. A sample groove 11 is provided at the inner bottom of the sample cell 1 for placing the sample. At the same time, the present application also does not limit the specific structures of the ablation laser and the microwave emitter 3, as long as they can emit the required light beams. The laser emitted by the ablation laser passes through the focusing lens 2 and the laser lens 9 and enters the sample cell 1, irradiating the sample to ablate the sample and turn the sample into small particle aerosols. The light beam emitted by the microwave emitter 3 enters the sample cell 1 through the laser lens 9 to further process the aerosols.

[0031] In the technical solution of the present invention, when detecting a liquid sample, after the sample is ablated by the ablation laser, aerosol particles of different sizes are generated in the sample. By the microwave emitted by the microwave emitter 3, the particle size of the aerosol particles becomes smaller, evaporates and finally atomizes. At the same time, the microwave can also remove the solvent in the aerosol particles, so that more solutes enter the inductively coupled plasma mass spectrometry for ionization analysis, thereby reducing the oxide interference in the detection process, improving the detection limit of elements, and enhancing the sensitivity, stability and analysis performance of the instrument. In addition, the memory effect and plasma matrix effect of the instrument are reduced, and more real, accurate high-precision element contents and isotope ratios are obtained. The present invention enables the laser ablation of liquid samples with small consumption, high sampling efficiency, and no need for sample dilution. The sampling amount of conventional geological samples can be reduced from 50-100 mg to 1-5 mg, which is particularly suitable for the analysis of precious geological samples, making it possible to directly analyze samples with low matrix effect, low mass loading effect, high salinity, high acidity and alkalinity, and high organic matter. During the sample extraction process and the sample pretreatment process, the consumption of acid and high-purity water will be reduced by more than 90%. The scale of waste acid and waste gas emissions is much lower than that of traditional ultra-clean rooms, which helps to achieve a miniaturized and localized ultra-clean experimental environment, realize the direct laser ablation extraction of various liquid samples, and achieve fast and efficient aerosol particle transmission.

[0032] Further, as Figure 1As shown, it further includes a shielding cover 4 covering the outside of the sample cell 1. An opening is provided at the top of the shielding cover 4. The focusing lens 2, the ablation laser, and the microwave transmitter 3 are all located outside the shielding cover 4. The laser emitted by the ablation laser and the microwave emitted by the microwave transmitter 3 both enter the sample cell 1 through the opening. In some embodiments, the shielding cover 4 is made of aluminum alloy material. Using this material has the effect of shielding the laser and can protect the staff. In some embodiments, the length of the shielding cover 4 is 200 - 205 mm, the width is 150 - 155 mm, and the height is 50 - 55 mm. Preferably, the length of the shielding cover 4 is 200 mm, the width is 150 mm, and the height is 50 mm. Making the shielding cover 4 of the same size is convenient for mass production. In some embodiments, observation windows 42 are provided on the front and rear side walls of the shielding cover 4, which is convenient for the staff to observe. A high-density brass mesh is laid on each observation window 42 to shield the hazards brought by the laser and the microwave and protect the staff.

[0033] Further, the microwave transmitter 3 includes a transmitting end. Among them, a limiting port 41 is provided at the top of the shielding cover 4, and the transmitting end extends into the shielding cover 4 through the limiting port 41. In this way, it is convenient to limit the microwave transmitter 3. In some embodiments, the distance between the transmitting end and the surface of the sample in the sample cell is 4 - 5 mm. Within this distance range, the microwave can act well on the aerosol.

[0034] Understandably, a soft high-density wire mesh is laid in the limiting port 41, and the transmitting end is clamped in the soft high-density wire mesh. In order to prevent the laser or the microwave from leaking from the limiting port 41 and hurting the staff, a soft high-density wire mesh is provided in the limiting port 41. The soft high-density wire mesh covers the outside of the transmitting end and is used to block the limiting port 41.

[0035] Specifically, the microwave transmitter 3 includes a resonant cavity 31 and a microwave source controller 32. The resonant cavity 31 includes a first end and a second end. The first end is used to emit microwaves towards the sample cell 1; the microwave source controller 32 is connected to the second end through a radio frequency line 33, as Figure 1As shown, the resonant cavity 31 is assembled from multiple parts made of stainless steel and brass. The tail of the resonant cavity 31 is provided with an interface for the RF cable 33. The microwave source controller 32 is connected to the resonant cavity 31 through the RF cable 33. Through the microwave source controller 32, the cylinder at the front end of the resonant cavity 31 releases continuous high-frequency microwaves. The operating frequency of the microwaves is 433 MHz, 915 MHz, 2.54 GHz or 5.80 GHz, the power is continuously adjustable from 10 - 200 W, set to 100 W, the power supply is 220 VAC, it is air-cooled, and has forward and reverse power monitoring.

[0036] Exemplarily, in order to place the resonant cavity 31 more stably, as Figure 1 shown, the resonant cavity 31 is arranged at a 45° downward tilt with the shielding cover 4 through the limiting port 41.

[0037] Further, the sample cell 1 is connected to a carrier pipeline 5 and an outlet pipeline 5. Among them, the carrier pipeline 5 is used to transport inert gas, and the inert gas can be helium, which is used to protect the sample from reacting with other components. In order to better protect the sample, the purity of helium can be 99.999%. In some embodiments, the gas flow rate in the carrier pipeline 5 is 650 - 655 mL / min, preferably 650 mL / min.

[0038] Specifically, the thickness of the laser lens 9 is 0.4 - 1 mm and / or, the transmittance of the 193 nm ultraviolet laser of the laser lens 9 is not less than 92%; and / or, the laser beam spot diameter emitted by the ablation laser is 100 - 105 µm; and / or, the pulse frequency emitted by the ablation laser is 5 - 10 Hz; and / or, the laser energy emitted by the ablation laser is 8 - 10 J·cm -2 , adopting the above technical solution can enable the laser to better ablate the sample.

[0039] Further, it further includes a total reflection mirror 7, which is arranged between the focusing lens 2 and the ablation laser, and is used to reflect the laser emitted by the ablation laser, so that the laser beam 8 is directed towards the focusing lens 2. The main function of the total reflection mirror 7 is to change the path of the laser beam 8 so that the laser beam 8 can always be directed towards the sample.

[0040] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. All equivalent structural transformations made under the inventive concept of the present invention, or direct / indirect applications in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A microwave-assisted laser dual-beam ablation cell, characterized in that: include: Sample cell, the top is sealed by laser lens; A focusing lens is located outside the sample pool and is arranged close to the laser lens; an ablation laser, the laser emitted by the ablation laser passes through the focusing lens and then passes through the laser lens into the sample cell; and A microwave transmitter, which transmits microwaves into the sample cell through the laser lens; The laser emitted by the ablation laser enters the sample pool through the focusing lens and the laser lens, and irradiates the sample to ablate the sample and turn the sample into aerosol of small particles. The light beam emitted by the microwave transmitter enters the sample pool through the laser lens to further process the aerosol. Wherein, the microwave transmitter comprises: a resonant cavity, comprising a first end and a second end, wherein the first end is used to emit microwaves toward the sample pool; and A microwave source controller connected to the second end portion via a radio frequency line; The microwave transmitter comprises a transmitting end, and the distance between the transmitting end and the sample surface in the sample pool is 4-5 mm.

2. The microwave-assisted laser dual-beam ablation cell according to claim 1, characterized in that: It also includes a shielding cover arranged outside the sample pool, and a hole is opened on the top of the shielding cover; The focusing mirror, the ablation laser and the microwave transmitter are all located outside the shielding cover, and the laser light emitted by the ablation laser enters the sample pool through the opening.

3. The microwave-assisted laser dual-beam ablation cell according to claim 2, characterized in that: The shielding cover is made of aluminum alloy material; and / or, The shielding cover has a length of 200-205 mm, a width of 150-155 mm, and a height of 50-55 mm; and / or, The front and rear side walls of the shielding cover are both provided with observation windows, and each observation window is covered with a high-density brass mesh.

4. The microwave-assisted laser dual-beam ablation cell according to claim 2, characterized in that: The microwave transmitter comprises a transmitting end, wherein: A limiting opening is provided on the top of the shielding cover, and the emitting end extends into the shielding cover through the limiting opening.

5. The microwave-assisted laser dual-beam ablation cell according to claim 4, characterized in that: A soft high-density wire mesh is laid in the limiting opening, and the emitting end is clamped in the soft high-density wire mesh.

6. The microwave-assisted laser dual-beam ablation cell according to claim 1, characterized in that: The sample pool is connected with a carrier pipeline and an air outlet pipeline, wherein: The carrier pipeline is used to transport inert gas; and / or, The flow rate of the gas in the carrier pipeline is 650-655 mL / min.

7. The microwave-assisted laser dual-beam ablation cell according to claim 1, characterized in that: The microwave frequency emitted by the microwave transmitter is 433 MHz, 915 MHz, 2.54 GHz or 5.80 GHz; and / or, The power of the microwave transmitter is 10-200W.

8. The microwave-assisted laser dual-beam ablation cell according to claim 1, characterized in that: The thickness of the laser lens is 0.4-1 mm; and / or, The 193nm ultraviolet laser transmittance of the laser lens is not less than 92%; and / or, The laser beam spot diameter emitted by the ablation laser is 100-105 μm; and / or, The pulse frequency emitted by the ablation laser is 5-10 Hz; and / or, The laser energy emitted by the ablation laser is 8-10 J·cm-2.

9. The microwave-assisted laser dual-beam ablation cell according to claim 1, characterized in that: It also includes a total reflection mirror, which is arranged between the focusing mirror and the ablation laser and is used to reflect the laser light emitted by the ablation laser so that the laser light is directed toward the focusing mirror.

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