Sample aerosol introduction device

Abstract

To provide a sample aerosol introduction device capable of suppressing memory effects.SOLUTION: A sample aerosol introduction device AA has a hydrophobic surface on the whole or a part of a wall forming a flow path for sample droplets, the surface being subjected to water-repellent treatment. For example, in the sample aerosol introduction device AA, an outer circumferential surface of a tip portion of a nebulizer 20A for atomizing a liquid sample and spraying sample droplets is a hydrophobic surface. For example, in the sample aerosol introduction device AA, an inner circumferential surface of a central tube of a plasma torch 40A is a hydrophobic surface. Since the whole or a part of the wall forming the flow path is a hydrophobic surface, sample droplets are less likely to remain inside the flow path, enabling suppression of memory effects.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sample atomization and introduction device, and more particularly to a sample atomization and introduction device that atomizes a liquid sample and introduces it into a sample introduction portion of an analyzer. [Background technology]

[0002] Known atomic spectrometry methods include plasma emission spectrometry, atomic absorption spectrometry, and atomic fluorescence spectrometry. Known mass spectrometry methods include plasma mass spectrometry and liquid chromatography mass spectrometry. Liquid chromatography using a light scattering detector is also known.

[0003] In analytical instruments used in these analytical methods, sample droplets obtained by atomizing a liquid sample are introduced into a sample introduction section, such as a plasma. Problems can arise when large sample droplets (coarse droplets) are introduced into the sample introduction section. For example, sample droplets introduced into the plasma are desolvated, and the elements contained in the droplets are excited or ionized, which are measured as emission intensity or ion count values. However, when coarse droplets are introduced into the plasma, time and energy are spent desolvating the sample droplets, resulting in insufficient excitation or ionization of the elements.

[0004] Therefore, large droplets are removed and only small sample droplets (fine droplets) are introduced into the sample introduction section. For example, after the liquid sample is atomized using a nebulizer to obtain sample droplets, the large droplets are removed by colliding with and adhering to the inner wall of the spray chamber using gravity and inertial force, and only the fine droplets are introduced into the sample introduction section.

[0005] When a liquid sample is atomized using a nebulizer, sample droplets may adhere to and remain on the outer surface of the nebulizer near the nozzle. The previous sample droplets that adhere to the outer surface of the nebulizer collide with the next sample droplets, gradually increasing in size and flowing into the nozzle. This re-atomization of the previous sample can lead to significant errors in the analytical results. Sample droplets ejected from the spray chamber may also adhere to and remain on the inner surface of the plasma torch. In this case, components contained in the remaining sample may be mixed into the next sample when it is measured, resulting in inaccurate measurement results. These phenomena are called the memory effect, and the former phenomenon in particular is called re-atomization.

[0006] One known countermeasure to the re-atomization phenomenon is to flow a nebulizer sheath gas so that it covers the vicinity of the nebulizer nozzle, thereby suppressing adhesion of sample droplets to the outer peripheral surface of the nebulizer. Another known method is to flow a sheath gas so that it covers the airflow of sample droplets being discharged from the spray chamber (Patent Document 1). This is thought to suppress adhesion of sample droplets to the inner peripheral surface of the plasma torch, thereby suppressing the memory effect.

[0007] Known spray chambers for removing coarse droplets include the double-tube type (also known as the Scott type) and the cyclone type. In either type of spray chamber, approximately 90-99% of the droplets introduced are discharged as drain, with approximately 1-10% being discharged as fine droplets. As a typical example, if the nebulizer spray rate is 0.6 mL / min and the proportion of droplets discharged as fine droplets is 5%, the discharge rate of fine droplets will be 30 μL / min.

[0008] When particle size selection is performed using a spray chamber, the flow rate of sample droplets introduced into the sample introduction section decreases, resulting in a decrease in analytical sensitivity. When the sample amount is large, the decrease in analytical sensitivity can be compensated for by extending the analysis time. However, when the sample amount is small, the decrease in analytical sensitivity becomes a major problem. In addition, if sample droplets adhere to the inner surface of the plasma torch, the amount of sample droplets introduced into the plasma decreases accordingly, further reducing analytical sensitivity.

[0009] To increase the transport efficiency of sample droplets into the plasma, a technique is known in which the entire amount of sample droplets sprayed from a micro-flow nebulizer is introduced into the plasma without using a spray chamber (Non-Patent Documents 1 and 2). This technique uses a long micro-flow nebulizer, such as a Direct Injection Nebulizer (commonly known as DIN) or a Direct Injection High Efficiency Nebulizer (commonly known as DIHEN). The central tube of the plasma torch is removed, and instead, a long micro-flow nebulizer is inserted into the plasma torch, with the nebulizer nozzle positioned 2 to 3 mm in front of the plasma.

[0010] Also known is a technique using a single-pipe spray chamber for total introduction (Non-Patent Document 3). In this technique, the spray chamber functions as a desolvator rather than a particle size selector. That is, the saturated water vapor pressure is, for example, about 30 g / m at 30°C. 3 (=30 mg / L), so if the spray rate of a micro-flow nebulizer is 30 μL / min, the solvent (water) in the droplets will evaporate in a short time with a nebulizer gas flow rate of 1 L / min. As a result, the sample droplets will become smaller, or the solvent will evaporate completely and become solid particles. The smaller the droplet size, the less loss there will be due to gravity settling and inertial collisions, and the more efficiently the sample droplets will be transported to the plasma. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] Japanese Patent Application Publication No. 6-102249 [Non-patent literature]

[0012] [Non-Patent Document 1] Direct injection nebulization for inductively coupled plasma mass spectrometry, Daniel R. Wiederin, Fred G. Smith, and RS Houk, Analytical Chemistry, Vol. 63, pp.219-225, 1991. [Non-patent document 2] A direct injection high-efficiency nebulizer for inductively coupled plasma mass spectrometry, John A. McLean, Hao Zhang, and Akbar Montaser, Analytical Chemistry, Vol. 70, pp.1012-1020, 1998. [Non-patent document 3] Total introduction of microsamples in inductively coupled plasma mass spectrometry by high-temperature evaporation chamber with a sheathing gas stream, Analytica Chimica Acta, Vol. 767, pp.14-20, 2013. Summary of the Invention [Problem to be solved by the invention]

[0013] In technologies that use nebulizer sheath gas flow near the nozzle of a nebulizer, increasing the flow rate of the nebulizer sheath gas to suppress sample droplet adhesion increases the total gas flow rate, which can make it difficult to operate under optimal excitation and ionization conditions. Therefore, there is a need for a technology that can effectively suppress sample droplet adhesion to the nebulizer even when the flow rate of the nebulizer sheath gas is reduced.

[0014] In the technology of flowing a sheath gas so as to cover the airflow of sample droplets discharged from the spray chamber, the sheath gas flow is maintained near the base end of the plasma torch, which has the effect of suppressing the adhesion of sample droplets. However, the sheath effect weakens near the tip of the plasma torch, and the adhesion of sample droplets is still unavoidable.

[0015] In the technology where the entire amount of sample droplets sprayed from a micro-flow nebulizer is introduced into the plasma, the droplets are introduced into the plasma at a higher speed than when using a spray chamber, resulting in a shorter residence time of the sample in the plasma. Furthermore, large droplets are also introduced directly into the plasma. This results in insufficient desolvation, excitation, and ionization in the plasma, which in turn reduces analytical sensitivity.

[0016] In the technology using a spray chamber for total introduction, sample droplets inevitably adhere to the inner wall of the spray chamber. Sample droplets also adhere to the inner surface of the plasma torch. Therefore, there is room for improvement in terms of the transport efficiency of sample droplets into the plasma.

[0017] In view of the above circumstances, an object of the present invention is to provide a sample atomization and introduction device that can suppress the memory effect. Another object of the present invention is to provide a sample atomization and introduction device that has high transport efficiency of sample droplets. [Means for solving the problem]

[0018] The first aspect of the sample atomization and introduction device is a sample atomization and introduction device that introduces sample droplets formed by atomizing a liquid sample into a sample introduction portion of an analytical device, and is characterized in that all or part of the wall surface that forms the flow path of the sample droplets is a water-repellent surface that has been treated with a water-repellent coating. The sample atomization and introduction device of the second aspect is characterized in that, in the first aspect, the water-repellent surface is a surface that has been lined with a fluorine-based resin, coated with a fluorine-based compound, coated with a silicone-based compound, or processed to form a nano- or micro-structure. A third aspect of the sample atomization and introduction device is the first or second aspect, wherein the water-repellent surface has a contact angle with water of 150° or more. The sample atomization and introduction device of the fourth aspect is characterized in that, in any of the first to third aspects, it comprises a nebulizer that atomizes the liquid sample to spray the sample droplets, and a nebulizer sheath gas flow path that flows a nebulizer sheath gas along the outer peripheral surface of the tip of the nebulizer, and the outer peripheral surface of the tip of the nebulizer is the water-repellent surface. The sample atomization and introduction device of the fifth aspect is any of the first to fourth aspects, and is characterized in that it comprises a plasma torch having a central tube through which the sample droplets flow, an intermediate tube into which the central tube is inserted and through which an auxiliary gas flows between the central tube and the intermediate tube, and an outer tube into which the intermediate tube is inserted and through which a plasma gas flows between the intermediate tube and the outer tube. The sample atomization and introduction device of a sixth aspect is the fifth aspect, characterized in that the inner peripheral surface of the central tube is the water-repellent surface. The seventh aspect of the sample atomization and introduction device is characterized in that, in the fifth or sixth aspect, the plasma torch further has a base end tube that is inserted into the base end of the central tube and through which central tube sheath gas flows between the plasma torch and the central tube. The sample atomization and introduction device of an eighth aspect is the seventh aspect, wherein the inner circumferential surface of the base end tube is the water-repellent surface. The ninth aspect of the sample atomization and introduction device is characterized in that, in the seventh or eighth aspect, it is provided with a nebulizer that atomizes the liquid sample and sprays the sample droplets, and the spray nozzle of the nebulizer is arranged inside the base tube. The sample atomization and introduction device of the 10th aspect is characterized in that, in any of the 5th to 9th aspects, the central tube has a gas inlet that introduces a portion of the auxiliary gas into the interior of the central tube and flows it as a central tube sheath gas. The sample atomization and introduction device of an eleventh aspect is the sample atomization and introduction device of any of the seventh to tenth aspects, characterized in that the central tube has a body portion with an inner diameter of 10 mm or more. The 12th aspect of the sample atomization introduction device is characterized in that, in any of the 5th to 10th aspects, the outer tube has a larger inner diameter at the rear end than at the front end, the intermediate tube has a larger inner diameter at the rear end than at the front end, and the central tube has a body with an inner diameter of 13 mm or more. The sample atomization and introduction device of a thirteenth aspect is characterized in that, in any one of the fifth to tenth aspects, the central tube has an inverted cone-shaped body portion whose inner diameter continuously decreases from the base end to the tip end. The sample atomization and introduction device of the 14th aspect is characterized in that, in any of the 5th to 10th aspects, the central tube has a body portion consisting of a cone-shaped rear portion whose inner diameter continuously increases from the base end to the middle portion, and an inverted cone-shaped front portion whose inner diameter continuously decreases from the middle portion to the tip. The sample atomization and introduction device of a fifteenth aspect is characterized in that, in any one of the fifth to fourteenth aspects, it further comprises a heater that heats the central tube sheath gas introduced into the central tube. The sample atomization and introduction device of the 16th aspect is characterized in that, in any of the first to fifteenth aspects, it comprises a nebulizer that atomizes the liquid sample to spray the sample droplets, a nebulizer sheath gas flow path that flows a nebulizer sheath gas along the outer peripheral surface of the tip of the nebulizer, and a humidifier that humidifies the nebulizer sheath gas. The sample atomization and introduction device of the 17th aspect is characterized in that, in any of the first to sixteenth aspects, it comprises a pump that delivers the liquid sample, and a splitter that supplies a portion of the liquid sample delivered from the pump to a nebulizer and discharges the remainder. [Effects of the Invention]

[0019] According to the first aspect, all or part of the wall surfaces constituting the flow channel are water-repellent, so that sample droplets are less likely to remain in the flow channel, and the memory effect can be suppressed. According to the second aspect, the wall surfaces that form the flow path can be made water-repellent. According to the third aspect, the sample droplets are easy to rebound even when they collide with the water-repellent surface, and are easy to detach even when they adhere to the water-repellent surface, so the sample droplets are less likely to remain on the water-repellent surface. According to the fourth aspect, the outer peripheral surface of the tip of the nebulizer is water-repellent, so that adhesion of sample droplets to the nebulizer can be effectively suppressed even when the flow rate of the nebulizer sheath gas is reduced, thereby suppressing the re-atomization phenomenon. According to the fifth aspect, the sample droplets can be introduced into the plasma. According to the sixth aspect, the inner peripheral surface of the central tube is a water-repellent surface, so that sample droplets are less likely to remain inside the central tube, and the memory effect can be suppressed. According to the seventh aspect, the central tube sheath gas flows along the inner circumferential surface of the central tube, so that sample droplets are less likely to adhere to the inner circumferential surface of the central tube. According to the eighth aspect, the inner peripheral surface of the base tube is water-repellent, so that sample droplets are less likely to remain inside the base tube, and the memory effect can be suppressed. According to the ninth aspect, since the nebulizer is directly mounted on the plasma torch, almost all of the sample droplets sprayed from the nebulizer are introduced into the plasma. This results in high transport efficiency of the sample droplets into the plasma. Furthermore, since the nebulizer's spray nozzle is located at the base end of the central tube, desolvation of the sample droplets progresses inside the central tube, facilitating excitation and ionization of the sample in the plasma. As a result, the analytical sensitivity of the analytical device is improved. According to the tenth aspect, a portion of the auxiliary gas is introduced into the central tube and flows as the central tube sheath gas, so that sample droplets are less likely to adhere to the inner surface of the central tube. Also, there is no need to provide a component for independently supplying the central tube sheath gas. According to the eleventh aspect, since the inner diameter of the body is large, the frequency of contact between the sample droplet and the inner circumferential surface of the body is reduced, and adhesion of the sample droplet can be suppressed. In addition, since the time until the sample droplet collides with the inner circumferential surface of the body is extended, desolvation can be facilitated accordingly. According to the twelfth aspect, the large inner diameter of the body of the central tube provides a high desolvation function. In addition, the shapes and dimensions of the front central tube, intermediate tube, and outer tube can be made the same as those of a general plasma torch, so that stable plasma can be maintained even when conditions such as gas flow rate and plasma output are set the same as those of a general plasma torch. According to the thirteenth aspect, since the body is in an inverted cone shape, the central tube sheath gas flow is maintained all the way to the tip of the central tube, which is highly effective in suppressing the adhesion of sample droplets. According to the fourteenth aspect, the rear part has a cone shape that follows the spread of sample droplets sprayed from the nebulizer, so that the dead volume is small and the signal peak can rise and fall quickly. According to the fifteenth aspect, the heated central tube sheath gas flows along the inner circumferential surface of the central tube, thereby accelerating desolvation of the sample droplets. According to the sixteenth aspect, by flowing humidified nebulizer sheath gas, the humidity around the nozzle of the nebulizer is increased, and the precipitation of salts contained in the liquid sample is suppressed, thereby suppressing clogging of the nozzle of the nebulizer with salts. According to the seventeenth aspect, the splitter allows the liquid sample to be supplied at a minute flow rate suitable for the nebulizer, and therefore the pump's liquid delivery flow rate can be increased to shorten the time it takes for the sample solution to reach the nebulizer. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is an overall view of a sample atomization and introduction device according to a first embodiment. [Figure 2] Figure (A) is a schematic diagram of the behavior of a droplet colliding with quartz glass, and Figure (B) is a schematic diagram of the behavior of a droplet colliding with a water-repellent surface. [Figure 3] FIG. 1 is a side view of a nebulizer according to a first embodiment. [Figure 4] 1 is a vertical cross-sectional view of a plasma torch according to a first embodiment. FIG. [Figure 5] FIG. 10 is a vertical cross-sectional view of a plasma torch according to a second embodiment. [Figure 6] FIG. 10 is a vertical cross-sectional view of a plasma torch according to a third embodiment. [Figure 7] 7A and 7B are cross-sectional views taken along the line VII-VII in FIG. 6, where FIG. 7A shows an example of a gas inlet, FIG. 7B shows another example of a gas inlet, and FIG. 7C shows yet another example of a gas inlet. [Figure 8] FIG. 1 is a longitudinal cross-sectional view of a plasma torch provided with a connector having a gas inlet. [Figure 9] FIG. 1 is a vertical cross-sectional view of a plasma torch having gas inlets provided at multiple positions. [Figure 10] FIG. 1 is a longitudinal cross-sectional view of a plasma torch that uses both a base end tube and a gas inlet. [Figure 11] FIG. 10 is an overall view of a sample atomization and introduction device according to a fourth embodiment. [Figure 12] FIG. 10 is a vertical cross-sectional view of a plasma torch according to a fourth embodiment. [Figure 13] FIG. 10 is a vertical cross-sectional view of a plasma torch according to a fifth embodiment. [Figure 14] FIG. 11 is a vertical cross-sectional view of another example of a plasma torch according to the fifth embodiment. [Figure 15] FIG. 10 is a vertical cross-sectional view of a plasma torch according to a sixth embodiment. [Figure 16] FIG. 13 is a vertical cross-sectional view of a plasma torch according to a seventh embodiment. [Figure 17] FIG. 13 is an overall view of a sample atomization and introduction device according to an eighth embodiment. [Figure 18] Graph (A) is a graph showing the change in signal intensity over time in Example 1. Graph (B) is a graph showing the change in signal intensity over time in Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0021] Next, an embodiment of the present invention will be described with reference to the drawings. [First embodiment] (Sample atomization introduction device) As shown in FIG. 1, the sample atomization and introduction device AA according to the first embodiment of the present invention is a component of an analytical device that analyzes liquid samples using analytical methods such as plasma emission spectrometry, plasma mass spectrometry, atomic absorption spectrometry, atomic fluorescence spectrometry, and liquid chromatography. The sample atomization and introduction device AA atomizes the liquid sample to generate sample droplets, and introduces the sample droplets into a sample introduction portion of the analytical device. The sample introduction portion is, for example, an excitation and ionization source such as plasma P. In liquid chromatography, the sample droplets are introduced into a light scattering detector. Such a detector is also included in the sample introduction portion.

[0022] The sample atomization and introduction device AA of this embodiment includes a sample supply source 10A, a nebulizer 20A, a spray chamber 30A, and a plasma torch 40A. The sample supply source 10A supplies a liquid sample to the nebulizer 20A. The sample supply source 10A includes, for example, a container 11 for storing the liquid sample, a flexible tube 12 connecting the container 11 and the nebulizer 20A, and a pump 13 disposed midway along the tube 12. The pump 13 may be, for example, a peristaltic pump.

[0023] Nebulizer 20A atomizes the liquid sample to generate sample droplets, which are then sprayed. Nebulizer 20A may be of any type, such as a coaxial type, crossflow type, or Babington type. For example, in the case of a coaxial type, tube 12 of sample supply source 10A is connected to the inner tube of nebulizer 20A, and the liquid sample is supplied through it. Nebulizer gas is introduced into the outer tube of nebulizer 20A. The liquid sample supplied to nebulizer 20A is atomized by the nebulizer gas, and is sprayed as sample droplets.

[0024] Nebulizer 20A is attached to spray chamber 30A. Sample droplets sprayed from nebulizer 20A are supplied to the interior of spray chamber 30A. Spray chamber 30A may be of any type, such as a single-tube type, a double-tube type (also called a Scott type), or a cyclone type.

[0025] Generally, spray chambers are broadly divided into two types based on functionality: those for particle size selection and those for total introduction. Spray chambers for particle size selection use inertial collision to selectively remove droplets with relatively large diameters (coarse droplets) and discharge only droplets with relatively small diameters (fine droplets). On the other hand, spray chambers for total introduction have a small droplet introduction amount (flow rate of droplets sprayed by the nebulizer), so the solvent (water) in the droplets evaporates and the droplets become finer. Since almost the entire amount of droplets introduced is discharged, the transport efficiency (= droplet discharge amount / droplet introduction amount) is high. Table 1 summarizes the standard specifications of the two types of spray chambers. The spray chamber 30A of this embodiment can be either type.

[0026] [Table 1]

[0027] The illustrated spray chamber 30A is a double-tube type. The spray chamber 30A has an inner tube 31 and an outer tube 32. The nebulizer 20A is held at the upper end of the inner tube 31. The lower end of the inner tube 31 is open and communicates with the internal space of the outer tube 32. A drain outlet 33 is provided at the bottom of the outer tube 32. A sample outlet 34 is provided at the top of the outer tube 32.

[0028] At least a portion of the sample droplets supplied from nebulizer 20A flows from the upper end to the lower end within the internal space of inner tube 31, then flows from the lower end to the upper end within the space between inner tube 31 and outer tube 32, and is discharged from sample outlet 34. Here, coarse droplets among the sample droplets supplied from nebulizer 20A collide with and adhere to the walls of inner tube 31 and outer tube 32, and become drain, which is discharged from drain outlet 33. Of the sample droplets, only fine droplets are discharged from sample outlet 34.

[0029] The sample outlet 34 of the spray chamber 30A is connected to the plasma torch 40A. The sample droplets discharged from the spray chamber 30A are supplied to the plasma torch 40A and introduced into the plasma P generated by the plasma torch 40A.

[0030] As described above, the sample droplets generated by the nebulizer 20A are introduced into a sample introduction portion, such as the plasma P, through a flow path formed by the spray chamber 30A, plasma torch 40A, etc. If the sample droplets adhere to and remain on the wall surfaces that form the sample droplet flow path, this can cause a memory effect. Therefore, in the sample nebulization and introduction device AA of this embodiment, all or part of the wall surfaces that form the sample droplet flow path are made water-repellent.

[0031] Here, the water-repellent surface refers to a surface of the wall constituting the flow path for the sample droplet that has been subjected to a water-repellent treatment. The water-repellent surface has water repellency. In addition to water repellency, the water-repellent surface may also have oil repellency. In particular, when using a liquid sample containing an organic solvent or a lipophilic solution, it is preferable that the water-repellent surface has oil repellency.

[0032] There are no particular limitations on the water-repellent treatment, as long as it imparts water repellency to the wall surface of the flow channel. Examples of substrates that make up the flow channel walls include glass, sapphire, and aluminum oxide. Water-repellent treatment imparts water repellency to the surface of the substrate. Examples of water-repellent treatments include 1) lining treatment with fluororesin, 2) coating treatment with fluorine-based compounds, 3) coating treatment with silicone-based compounds, and 4) nano- and micro-structure formation treatment.

[0033] 1) Lining with a fluororesin may be performed by attaching a fluororesin sheet to the wall surface of the flow path, or by inserting a fluororesin tube into the inner surface of the tubular flow path and making it adhere tightly. Examples of fluororesins include polytetrafluoroethylene (PTFE), perfluoroalkoxyalkane (PFA), perfluoroethylenepropene copolymer (FEP), ethylenetetrafluoroethylene copolymer (ETFE), and polyvinylidene fluoride (PVDF).

[0034] Fluorine-based resins have a large contact angle with water and are highly water-repellent. The contact angles with water are 112° for PTFE, 115° for PFA, and 115° for FEP. Fluorine-based resins are not only water-repellent but also oil-repellent. The water-repellent surface formed by this method is characterized by its long-lasting water- and oil-repellent properties. Furthermore, the water-repellent surface formed by this method is resistant to samples containing hydrofluoric acid. Note that other water-repellent materials may be used instead of fluororesin. It is preferable that the water-repellent material have the same water- and oil-repellent properties as fluororesin, and also have excellent chemical resistance, heat resistance, UV resistance, and cleanability.

[0035] 2) Coating with fluorine-based compounds is a process in which a fluorine-based compound dissolved in a solvent is coated on the wall surface of a flow channel by painting, dipping, spraying, or other methods. Various compounds (except resins) can be used as the fluorine-based compound, but from the viewpoint of practical durability, fluorine-based silane coupling compounds that chemically bond with glass are preferably used. Fluorine-based silane coupling compounds are substances in which a silane coupling agent and a fluorine compound are bonded. The silane coupling agent may be any agent that chemically bonds with the hydroxyl group [-OH] of glass, and is not particularly limited, but is, for example, a substance having a trialkoxysilyl group [-Si-(OR)3]. Fluorine compounds include perfluoroalkyl [-CF 17 , -CF 13 etc.], perfluoropolyether [C3F7-(O-CF2-CF2-CF2-) n -C2F4-, etc.], but are not limited to these, and known coatings can be used. A coating of a fluorine-based compound that does not chemically bond to glass may also be used as long as it has practical durability equivalent to that of a coating of a fluorine-based silane coupling compound.

[0036] Surfaces coated with fluorine-based compounds are characterized by their super-water-repellent properties, with contact angles with water exceeding 150°. Such super-water-repellent surfaces can effectively prevent sample droplets from adhering. Commercially available super-water-repellent fluorine-based coating agents include SF Coat (registered trademark) from AGC Seimi Chemical Co., Ltd., Fluorosurf (registered trademark) from Fluoro Technology Co., Ltd., and TC-10S from Yoshida SKT Co., Ltd.

[0037] In order for the surface of a solid material to exhibit water repellency or super-water repellency, the surface free energy must be reduced. Lining with a fluororesin such as PTFE is an effective way to achieve this. However, because the resin surface is smooth with fluororesin lining, the maximum contact angle with water is 115°, and super-water repellency is not achieved. To achieve super-water repellency, it is necessary to introduce fine irregularities into the surface and enhance the water-repellent surface properties. Some fluororesin coatings can form fractal structures or hierarchical irregular structures on the surface, which can achieve super-water repellency.

[0038] 3) Silicone compound coating is a process in which a silicone compound is coated on the wall surface of a flow path. Silicone compound coating agents are disclosed in JP 2009-137775 A, JP 2018-1933 A, and the like. Commercially available products include MRS-102 from Yoshida SKT Co., Ltd. and polysilsesquioxane from KRI Co., Ltd. This method is characterized by the absence of concerns about environmental pollution caused by fluorine compounds.

[0039] 4) Nano- and micro-structure formation processing is a process that physically creates minute irregularities or fractal structures on the wall surface of a channel to impart water-repellent or water- and oil-repellent properties. For example, a lotus leaf structure can be formed on the wall surface of a channel. Processing methods that can be used include laser processing, glass molding (a method of transferring a mold with a nanostructure onto the glass surface), and self-organization. A water-repellent surface formed by this method has the characteristic of maintaining its water- and oil-repellent properties for a relatively long period of time.

[0040] Table 2 summarizes the characteristics of the four types of water-repellent treatments. [Table 2]

[0041] Figure 2(A) is a schematic diagram of the behavior of a droplet impacting a silica glass surface. Silica glass is hydrophilic, with a contact angle θ of approximately 20° with water. Therefore, when a droplet impacts a silica glass surface, it adheres to the surface. Figure 2(B) is a schematic diagram of the behavior of a droplet impacting a water-repellent surface. Water-repellent surfaces have a large contact angle θ with water. For example, the contact angle θ of PTFE with water is approximately 110°, and the contact angle θ of a glass surface coated with FluoroSurf® is 150° or more. When a droplet impacts a water-repellent surface, it assumes a spherical shape. Therefore, the droplet is likely to recoil even after impacting the water-repellent surface. Furthermore, droplets that adhere to the water-repellent surface have a large cross-sectional area exposed to the gas flow, making them susceptible to the gas flow. In addition, droplets have a small contact area with the water-repellent surface, resulting in weak adhesion. Therefore, even if a droplet adheres to a water-repellent surface, it tends to slide and rotate, easily detaching from the water-repellent surface. As a result, droplets are less likely to remain on the water-repellent surface.

[0042] It is preferable that the water-repellent surface has a contact angle with water of 150° or more. This allows sample droplets to easily bounce off even when they collide with the water-repellent surface. Also, even if sample droplets adhere to the water-repellent surface, they are easily detached. Therefore, sample droplets are less likely to remain on the water-repellent surface.

[0043] As described above, by making all or part of the wall surfaces constituting the flow path water-repellent, sample droplets are less likely to remain in the flow path. As a result, the memory effect can be suppressed. There are no particular restrictions on the wall surfaces that can be made water-repellent, but it is effective to make wall surfaces on which sample droplets are likely to remain water-repellent. Below, we will explain an example in which the outer peripheral surface of nebulizer 20A is made water-repellent, and an example in which the inner peripheral surface of the central tube of plasma torch 40A is made water-repellent.

[0044] (Nebulizer) As shown in Figure 3, nebulizer 20A is held in end cap 35 attached to the end of spray chamber 30A. More specifically, the tip of nebulizer 20A is inserted into a through-hole formed in end cap 35. A gap is formed between the inner circumferential surface of the through-hole and the outer circumferential surface of nebulizer 20A. This gap is called nebulizer sheath gas flow path 36. End cap 35 has nebulizer sheath gas supply port 37 that communicates with nebulizer sheath gas flow path 36.

[0045] When nebulizer sheath gas is supplied to nebulizer sheath gas supply port 37, the nebulizer sheath gas flows through nebulizer sheath gas flow path 36. That is, the nebulizer sheath gas flows along the outer peripheral surface of the tip of nebulizer 20A. The action of the nebulizer sheath gas can prevent sample droplets from adhering to the outer peripheral surface of nebulizer 20A.

[0046] If the nebulizer sheath gas flow rate is low, some of the sample droplets may break through the sheath gas flow and adhere to the outer surface of the nebulizer 20A. If the nebulizer sheath gas flow rate is increased to prevent sample droplets from adhering, the total gas flow rate, including the nebulizer gas, will increase. This can make it difficult to operate under optimal excitation and ionization conditions.

[0047] Therefore, in this embodiment, the outer peripheral surface of the tip of nebulizer 20A is made into water-repellent surface 20r. Here, the tip of nebulizer 20A includes the spray nozzle from which the sample droplets are sprayed, and refers to a range of a predetermined length from the spray nozzle in the axial direction. Water-repellent surface 20r may be the same area as the surface that constitutes nebulizer sheath gas flow path 36, or it may be a longer or shorter area in the axial direction. Alternatively, the tip surface of nebulizer 20A may be made into water-repellent surface 20r.

[0048] If the outer peripheral surface of the tip of nebulizer 20A is made water-repellent 20r, even if sample droplets adhere, they can be blown away by a small flow rate of nebulizer sheath gas. In other words, even if the flow rate of nebulizer sheath gas is reduced, adhesion of sample droplets to nebulizer 20A can be effectively suppressed. As a result, re-atomization can be suppressed. Furthermore, if the tip surface of nebulizer 20A is made water-repellent 20r, adhesion of sample droplets to the spray nozzle of nebulizer 20A can be suppressed. This prevents clogging of the spray nozzle due to the deposition of salts.

[0049] (Plasma Torch) As shown in Figure 4, plasma torch 40A has a triple-tube structure consisting of a central tube 41, an intermediate tube 42, and an outer tube 43. Intermediate tube 42 is inserted inside outer tube 43. Central tube 41 is inserted inside intermediate tube 42. Sample droplets flow together with nebulizer gas through the inner flow path inside central tube 41. Auxiliary gas flows through the intermediate flow path formed between intermediate tube 42 and central tube 41. Plasma gas flows through the outer flow path formed between outer tube 43 and intermediate tube 42.

[0050] If sample droplets adhere to the inner peripheral surface of the central tube 41, this will cause a memory effect. Therefore, in this embodiment, the inner peripheral surface of the central tube 41 is made to be a water-repellent surface 41r. Because the inner peripheral surface of the central tube 41 is a water-repellent surface 41r, sample droplets are less likely to remain inside the central tube 41, and the memory effect can be suppressed.

[0051] The tip of the central tube 41 (within a range of 2 to 3 mm in the axial direction from the tip) is exposed to high temperatures from the plasma P. If the water-repellent surface 41r is formed by lining with a fluororesin, the high temperatures from the plasma P may melt or decompose the fluororesin, releasing carbon and fluorine and interfering with the analysis. Furthermore, the molten fluororesin may deform the tip of the central tube 41, potentially reducing the sensitivity of the analytical device. In such cases, it is preferable to form the water-repellent surface 41r on the inner circumferential surface of the central tube 41, excluding the tip. On the other hand, if the water-repellent surface 41r is formed by coating with a fluorine-based compound, the above-mentioned problems are less likely to occur. Therefore, the entire inner circumferential surface of the central tube 41 may be formed as the water-repellent surface 41r.

[0052] The plasma torch is often positioned vertically upward in an ICP optical emission spectrometer and horizontally in ICP mass spectrometry, but this is not a limitation. If the plasma torch is positioned vertically downward, the sample droplets fall vertically, further reducing the possibility of the sample droplets adhering to the inner surface of the central tube 41.

[0053] Second Embodiment Next, a sample atomization and introduction device BB according to a second embodiment will be described. 5, the plasma torch 40B of this embodiment has a configuration in which a central tube sheath gas flows along the inner peripheral surface of the central tube 41. The plasma torch 40B has a base end tube 44. The base end tube 44 is a tubular member that is shorter than the central tube 41, and is inserted into the base end of the central tube 41. The inner diameter of the body of the central tube 41 is usually 4 mm, but it is preferable to widen this to 6 to 8 mm before inserting the base end tube 44.

[0054] A gap is formed between the inner circumferential surface of the central tube 41 and the outer circumferential surface of the base end tube 44. This gap is called the central tube sheath gas flow path 45. The central tube 41 has a branch pipe 46 that communicates with the central tube sheath gas flow path 45. When central tube sheath gas is supplied to the branch pipe 46, the central tube sheath gas flows through the central tube sheath gas flow path 45. The central tube sheath gas then flows along the inner circumferential surface of the central tube 41. Therefore, sample droplets are less likely to adhere to the inner circumferential surface of the central tube 41.

[0055] The inner peripheral surface of the base end tube 44 may be made into a water-repellent surface 44r. In this way, sample droplets are less likely to remain inside the base end tube 44, and the memory effect can be suppressed. However, the inner peripheral surface of the base end tube 44 does not have to be made into a water-repellent surface 44r. The gap between the inner peripheral surface of the central tube 41 and the outer peripheral surface of the base end tube 44 is preferably 0.2 to 1.0 mm, although this depends on the flow rate of the central tube sheath gas. Furthermore, the inner peripheral surface of the central tube 41 may or may not be made into a water-repellent surface 41r.

[0056] Third Embodiment Next, a sample atomization and introduction device CC according to a third embodiment will be described. The configuration for flowing the central tube sheath gas inside the central tube 41 is not limited to the configuration using the base end tube 44 shown as the second embodiment. For example, a configuration may be adopted in which a part of the auxiliary gas is introduced into the central tube 41 and flows as the central tube sheath gas.

[0057] As shown in Figure 6, a plasma torch 40C of this embodiment has a gas inlet 48 formed in the central tube 41. The gas inlet 48 is an opening that connects the inside and outside of the central tube 41. A portion of the auxiliary gas flowing outside the central tube 41 passes through the gas inlet 48 and is introduced into the inside of the central tube 41. The auxiliary gas introduced into the inside of the central tube 41 flows along the inner surface of the central tube 41 as central tube sheath gas. Therefore, sample droplets are less likely to adhere to the inner surface of the central tube 41.

[0058] To control the flow of the auxiliary gas (central tube sheath gas), it is preferable to provide an auxiliary gas separation pipe 48a and a sheath gas formation pipe 48b inside and outside the central tube 41. The auxiliary gas separation pipe 48a is provided outside the central tube 41. A gap is formed between the outer peripheral surface of the central tube 41 and the inner peripheral surface of the auxiliary gas separation pipe 48a, and this gap serves as the auxiliary gas separation flow path. The auxiliary gas separation flow path is connected to the gas inlet 48. The sheath gas formation pipe 48b is provided inside the central tube 41. A gap is formed between the inner peripheral surface of the central tube 41 and the outer peripheral surface of the sheath gas formation pipe 48b, and this gap serves as the sheath gas formation flow path. The sheath gas formation flow path is connected to the gas inlet 48.

[0059] The auxiliary gas introduced into the branch pipe 47 flows through the intermediate flow path between the intermediate pipe 42 and the central pipe 41. A portion of the auxiliary gas passes through the auxiliary gas separation flow path between the central pipe 41 and the auxiliary gas separation pipe 48a, and then passes through the gas inlet 48. The auxiliary gas that has passed through the gas inlet 48 passes through the sheath gas formation flow path between the central pipe 41 and the sheath gas formation pipe 48b as central pipe sheath gas. The central pipe sheath gas has its direction aligned by flowing through the sheath gas formation flow path, and flows along the inner surface of the central pipe 41.

[0060] The proportion of the auxiliary gas introduced into the branch pipe 47 that is introduced into the interior of the central pipe 41 as central pipe sheath gas is determined by the ratio of the annular cross-sectional area of ​​the intermediate flow passage between the intermediate pipe 42 and the central pipe 41 to the annular cross-sectional area of ​​the auxiliary gas separation flow passage between the central pipe 41 and the auxiliary gas separation pipe 48a, as well as the back pressure of each flow passage. In addition, the sheath gas formation pipe 48b has the function of flowing the central pipe sheath gas along the inner surface of the central pipe 41 at a constant speed regardless of its position on the inner circumference.

[0061] There are no particular limitations on the configuration of gas inlet 48 as long as it allows gas to flow through it. Examples of the configuration of gas inlet 48 include tangential through-holes as shown in Fig. 7(A), radial through-holes as shown in Fig. 7(B), and an annular porous material as shown in Fig. 7(C).

[0062] In this embodiment, a portion of the auxiliary gas is used as the central tube sheath gas, eliminating the need for a separate central tube sheath gas supply. This eliminates the need for the base pipe 44, branch pipe 46, mass flow controller, and other components required for an independent supply of central tube sheath gas. Furthermore, the gas inlet 48, auxiliary gas fractionation pipe 48a, and sheath gas formation pipe 48b are not limited to being located near the base end of the central tube 41; they can be located anywhere on the central tube 41 as long as steric hindrance is not an issue. Depending on the required flow rate of the central tube sheath gas and the thickness of the sheath layer, one or both of the auxiliary gas fractionation pipe 48a and the sheath gas formation pipe 48b may be omitted.

[0063] 8, the central tube 41 may be divided into a front portion and a rear portion, which may be connected by a connector 48c having a gas inlet 48. In this case, an auxiliary gas separation pipe 48a may be provided on the outside of the connector 48c, and a sheath gas generation pipe 48b may be provided on the inside of the connector 48c. Even in this configuration, a portion of the auxiliary gas is introduced into the central tube 41 through the gas inlet 48.

[0064] As shown in FIG. 9, gas inlets 48 may be provided at multiple positions along the axial direction of the central tube 41. In the illustrated example, gas inlets 48 are provided at two locations on the central tube 41. Alternatively, the entire series of flow paths consisting of the auxiliary gas separation flow path, the gas inlets 48, and the sheath gas formation flow path may be inclined with respect to the central axis of the central tube 41. Here, the flow paths are inclined from the outside to the inside of the central tube 41 as they move from the base end to the tip end of the central tube 41. This configuration facilitates the introduction of the auxiliary gas into the central tube 41. In the illustrated example, the cross-sectional shapes of the auxiliary gas separation pipe 48a and the sheath gas formation pipe 48b are triangular, but the cross-sectional shapes are not limited to this.

[0065] As shown in Figure 10, a base tube 44 and a gas inlet 48 may be used together. The central tube sheath gas flow formed by the central tube sheath gas flow path 45 between the central tube 41 and the base tube 44 has a sheath effect that weakens the farther it is from the base tube 44. Therefore, sample droplets tend to adhere to the portion of the central tube 41 where the inner diameter becomes smaller, particularly near the tip of the central tube 41. In contrast, in the example shown, a gas inlet 48 is provided near the tip of the central tube 41.

[0066] More specifically, the central tube 41 is divided into a body portion 41t and a nozzle portion 41n, which are connected by a connector 48c. The gas inlet 48 is preferably provided in the connector 48c near the body portion 41t. A portion of the auxiliary gas is introduced into the interior of the central tube 41 through the gas inlet 48. Because the auxiliary gas is introduced near the tip of the central tube 41, it is easy to suppress the adhesion of sample droplets in this area. In this way, a gas flow with a high sheath effect can be formed near the tip of the central tube 41. A configuration capable of forming such a gas flow has not been reported until now.

[0067] [Fourth embodiment] Next, a sample atomization and introduction device DD according to a fourth embodiment will be described. The sample atomization and introduction device DD of this embodiment is mainly used for analyzing minute amounts of samples. Fields requiring analysis of minute amounts of samples include life science, space science, and advanced materials. Even when a large amount of sample is required, a small amount of sample is introduced into a liquid chromatograph or electrophoresis device, and multiple components in the sample are separated and analyzed while maintaining a high level of separation. The sample atomization and introduction device DD is also used in such cases.

[0068] As shown in FIG. 11, the sample supply source 10D of this embodiment is configured to perform flow injection analysis (FIA). The sample supply source 10D includes a syringe 14, a liquid delivery pump 15, and a six-way valve 16. After the sample collected in the syringe 14 is injected into the sampling loop of the six-way valve 16, the six-way valve 16 is switched to introduce a carrier solution (such as dilute nitric acid) delivered from the liquid delivery pump 15 into the sampling loop. This introduces the sample sealed in the sampling loop into the nebulizer 20D. Note that a separation column or electrophoresis unit may be installed between the six-way valve 16 and the nebulizer 20D to form a liquid chromatograph or electrophoresis device.

[0069] Because the amount of liquid sample supplied to the nebulizer 20D is small, it is preferable to use a microflow nebulizer as the nebulizer 20D. A typical nebulizer can stably spray sample droplets at a flow rate of approximately 0.5 to 1.0 mL / min. In contrast, a microflow nebulizer can stably spray sample droplets even at a flow rate of approximately 300 μL / min or less.

[0070] When a minute flow of sample droplets is introduced into a double-tube spray chamber, the sample may be diluted as it passes through the spray chamber, and the high level of separation of each component may be lost. Therefore, in the sample atomization introduction device DD of this embodiment, the nebulizer 20D is directly connected to the plasma torch 40D.

[0071] As shown in Fig. 12, plasma torch 40D has a triple-tube structure consisting of a central tube 41, an intermediate tube 42, and an outer tube 43. Plasma torch 40D also has a base tube 44. Nebulizer 20D is connected to base tube 44 via a connector 50. The spray nozzle of nebulizer 20D is located inside base tube 44. Note that instead of a configuration having base tube 44, a configuration in which a gas inlet 48 is provided in central tube 41 may be used, as shown in Figs. 6 to 10.

[0072] Generally, the inner diameter of the central tube 41 is smaller than the inner diameter of the spray chamber. Therefore, a nebulizer 20D that can be inserted into a central tube 41 with a small inner diameter and that produces a small spray angle of sample droplets is preferred. The slower the radial velocity of the sample droplets compared to their axial velocity, the smaller the spray angle of the sample droplets. From this perspective, a coaxial nebulizer, an inkjet nebulizer, or the like is suitable for the nebulizer 20D. Inkjet nebulizers are particularly suitable because the ejected droplets travel in a nearly straight line, except for a slight settling due to gravity.

[0073] Connector 50 is a tubular member into which nebulizer 20D is inserted. A gap is formed between the inner peripheral surface of connector 50 and the outer peripheral surface of nebulizer 20D. This gap is called nebulizer sheath gas flow path 51. Connector 50 has nebulizer sheath gas supply port 52 that communicates with nebulizer sheath gas flow path 51.

[0074] When nebulizer sheath gas is supplied to nebulizer sheath gas supply port 52, the nebulizer sheath gas flows through nebulizer sheath gas flow path 51. That is, the nebulizer sheath gas flows along the outer peripheral surface of the tip of nebulizer 20D. The action of the nebulizer sheath gas can prevent sample droplets from adhering to the outer peripheral surface of nebulizer 20D.

[0075] The outer peripheral surface of the tip of nebulizer 20D may be made into water-repellent surface 20r. This effectively prevents sample droplets from adhering to nebulizer 20D even when the flow rate of nebulizer sheath gas is reduced. However, the outer peripheral surface of nebulizer 20D does not have to be made into water-repellent surface 20r. In particular, inkjet-type nebulizers are generally designed to prevent sample droplets from adhering, so water-repellent surface 20r is often not required. Furthermore, the inner peripheral surface of base tube 44 may or may not be made into water-repellent surface 44r. The inner peripheral surface of central tube 41 may or may not be made into water-repellent surface 41r.

[0076] In this embodiment, since the nebulizer 20D is directly mounted on the plasma torch 40D, as long as the sample droplets do not adhere to the inner circumferential surface of the central tube 41, almost all of the sample droplets sprayed from the nebulizer 20D are introduced into the plasma P. This increases the efficiency of transporting the sample droplets to the plasma P. In particular, by flowing the central tube sheath gas along the inner circumferential surface of the central tube 41 and making the inner circumferential surface of the central tube 41 a water-repellent surface 41r, the adhesion of the sample droplets to the inner circumferential surface of the central tube 41 can be suppressed. As a result, the efficiency of transporting the sample droplets to the plasma P can be further increased.

[0077] Furthermore, because the spray nozzle of nebulizer 20D is located at the base end of central tube 41, central tube 41 functions similarly to a spray chamber for introducing the entire sample. Specifically, as sample droplets flow through central tube 41, desolvation is promoted by the nebulizer sheath gas and central tube sheath gas. Furthermore, high-speed sample droplets sprayed from nebulizer 20D collide with the gas inside central tube 41 and decelerate. Since the desolvated sample droplets with a slower flow rate are introduced into plasma P, the energy required for desolvation in plasma P is reduced, and the residence time of the sample droplets in plasma P is extended, facilitating excitation and ionization of the sample in plasma P. As a result, the analytical sensitivity of the analyzer is improved.

[0078] In order to prevent sample droplets from adhering to the inner surface of the central tube 41, it is preferable that the interior of the central tube 41 does not have any uneven structures, such as an impactor that impacts large droplets. In other words, it is preferable that the inner surface of the central tube 41 is a smooth surface without any large unevenness.

[0079] Furthermore, to enhance the desolvation function of the central tube 41, it is preferable to make the inner diameter of the central tube 41 larger than usual. Here, the central tube 41 is composed of a body section 41t with a relatively large inner diameter, a nozzle section 41n with a relatively small inner diameter, and a connecting section 41c that continuously connects the body section 41t and the nozzle section 41n. The nozzle section 41n is disposed on the plasma P side. Of these sections of the central tube 41, it is preferable to make the inner diameter of the body section 41t larger. Note that, although not particularly limited, the lengths of the body section 41t, the connecting section 41c, and the nozzle section 41n are 60 to 80%, 5 to 15%, and 10 to 35% of the total length of the central tube 41, respectively. The total length of the central tube 41 is 80 to 100 mm. Furthermore, the body section 41t mainly includes the portion forward of the branch pipe 47 that introduces the auxiliary gas.

[0080] A typical plasma torch has an outer tube with an inner diameter of approximately 18 mm, an intermediate tube with an inner diameter of approximately 14 mm, a central tube with an inner diameter of 4 mm, and a nozzle with an inner diameter of 1 to 2.5 mm. While using such typical outer and intermediate tubes, the inner diameter of the central tube may be increased. For example, if the gap between the intermediate tube 42 and the central tube 41 (the thickness of the intermediate passage through which the auxiliary gas flows) is 1 mm and the wall thickness of the central tube 41 is 1 mm, the inner diameter of the body portion 41t of the central tube 41 can be 10 mm. Furthermore, by reducing the wall thicknesses of the outer tube 43, intermediate tube 42, and central tube 41 and reducing the thicknesses of the outer and intermediate passages, the inner diameter of the body portion 41t of the central tube 41 can be increased by an additional 2 to 3 mm. In other words, even when a typical outer tube 43 and intermediate tube 42 are used, the inner diameter of the body portion 41t of the central tube 41 can be increased to 10 to 13 mm.

[0081] Sample droplets sprayed from nebulizer 20D travel not only in the axial direction but also in the radial direction. Increasing the inner diameter of body 41t increases the time it takes for sample droplets to collide with the inner surface of body 41t. This increases the proportion of sample droplets that reach nozzle 41n in front of them before contacting the inner surface of body 41t, reducing the frequency of contact between sample droplets and the inner surface of body 41t and suppressing adhesion of sample droplets. Furthermore, since the time it takes for sample droplets to collide with the inner surface of body 41t is increased, desolvation is facilitated accordingly.

[0082] In conventional plasma torches, the central tube only functions as a flow path for introducing sample droplets into the plasma. Therefore, the dead volume of this flow path must be reduced, and the inner diameter of the central tube's body has generally been set to approximately 4 mm. In contrast, in this embodiment, the central tube 41 must have a larger inner diameter in order to function as a spray chamber for introducing the entire amount of sample. As a result of extensive experiments conducted by the applicant, it has been confirmed that the memory effect can be significantly reduced by setting the inner diameter of the body 41t of the central tube 41 to 10 mm or more and flowing a central tube sheath gas.

[0083] The solvent removal function of the central tube 41 can also be improved by making the body portion 41t longer than usual.

[0084] To enhance the desolvation function of the central tube 41, heated central tube sheath gas may be introduced into the central tube 41. The saturated water vapor pressure increases with increasing temperature. Specifically, the saturated water vapor pressure is 30 g / m at 30°C. 3 , 123 g / m at 50°C 3 , 595 g / m at 100°C 3 These are equilibrium values, and when the evaporation rate is taken into account, the amount of water vapor in the central tube sheath gas will be lower than these values. However, it is clear that desolvation proceeds more easily as the temperature increases.

[0085] Therefore, the sample atomization introduction device DD of this embodiment has a heater 61 that heats the central tube sheath gas. The heater 61 is arranged outside the plasma torch 40D. The central tube sheath gas heated by the heater 61 is introduced into the interior of the central tube 41 from the branch tube 46. The heated central tube sheath gas flows along the inner circumferential surface of the central tube 41, accelerating desolvation of the sample droplets.

[0086] Auxiliary gas at room temperature flows through the intermediate flow path between the central tube 41 and the intermediate tube 42. Therefore, even if heated central tube sheath gas is introduced into the central tube 41, the central tube 41 itself is cooled by the auxiliary gas and the temperature does not increase. The inner peripheral surface of the central tube 41 is kept at a temperature several tens of degrees lower than the temperature of the central tube sheath gas, so deterioration of the water-repellent surface 41r does not occur easily.

[0087] When the spray nozzle of nebulizer 20D is exposed to heated central tube sheath gas, salts contained in the liquid sample precipitate, making the nozzle more susceptible to clogging. In particular, coaxial nebulizers for microflow rates are more susceptible to clogging than typical coaxial nebulizers because the inner tube through which the liquid sample flows has a small inner diameter of 50 to 150 μm and the gap between the inner tube and outer tube through which the nebulizer gas flows is narrow, at 10 to 30 μm. However, if the spray nozzle of nebulizer 20D is located inside the base tube 44, the heated central tube sheath gas is blocked by the base tube 44 and does not directly hit the spray nozzle of nebulizer 20D. This suppresses the precipitation of salts contained in the liquid sample and makes the spray nozzle less likely to clog. The spray nozzle of nebulizer 20D may be located slightly forward of the base tube 44, as long as it is not directly hit by the central tube sheath gas.

[0088] It is preferable to use the nebulizer sheath gas at room temperature without heating it. Furthermore, humidifying the nebulizer sheath gas can further prevent clogging of the spray nozzle of the nebulizer 20D. The sample atomization and introduction device DD of this embodiment has a humidifier 62 that humidifies the nebulizer sheath gas. The humidifier 62 is located outside the plasma torch 40D. A bubbler, for example, can be used as the humidifier 62. The nebulizer sheath gas is bubbled with a bubbler containing water to incorporate water vapor into the nebulizer sheath gas. The humidified nebulizer sheath gas is introduced into the nebulizer sheath gas flow path 51.

[0089] By flowing humidified nebulizer sheath gas, the humidity around the nozzle of nebulizer 20D increases, suppressing the precipitation of salts contained in the liquid sample. As a result, clogging of the nozzle of nebulizer 20D with salts can be suppressed. In this way, by using both central tube sheath gas and nebulizer sheath gas, clogging of the nozzle of nebulizer 20D can be suppressed while improving the desolvation function.

[0090] Although this humidification operation increases the amount of water vapor in the nebulizer sheath gas, the high-temperature central tube sheath gas flowing outside it has a high desolvation function, so the impact on the overall desolvation function is limited.

[0091] The nebulizer sheath gas is usually argon gas, the same as the plasma gas, but the nebulizer sheath gas may also contain helium gas, hydrogen gas, nitrogen gas, etc., as long as the plasma P does not become unstable.

[0092] Fifth Embodiment Next, a sample atomization and introduction device EE according to a fifth embodiment will be described. As shown in Figure 13, in the sample atomization and introduction device EE of this embodiment, a nebulizer 20E is directly connected to a plasma torch 40E. The plasma torch 40E has a triple-tube structure consisting of a central tube 41, an intermediate tube 42, and an outer tube 43. The plasma torch 40E also has a base tube 44. The nebulizer 20E is connected to the base tube 44 via a connector 50.

[0093] The outer peripheral surface of the tip of nebulizer 20E may be water-repellent surface 20r. The inner peripheral surface of connector 50, particularly the inner peripheral surface of the portion that widens into a cone shape, may be water-repellent surface 50r. The inner peripheral surface of base tube 44 may be water-repellent surface 44r. The inner peripheral surface of central tube 41 may be water-repellent surface 41r. However, the outer peripheral surface of the tip of nebulizer 20E does not have to be water-repellent surface 20r, the inner peripheral surface of connector 50 does not have to be water-repellent surface 50r, the inner peripheral surface of base tube 44 does not have to be water-repellent surface 44r, and the inner peripheral surface of central tube 41 does not have to be water-repellent surface 41r.

[0094] In this embodiment, the plasma P side of the plasma torch 40E, defined by the joint between the connecting portion 41c of the central tube 41 and the nozzle portion 41n, is referred to as the front portion, and the nebulizer 20E side of the joint between the body portion 41t of the central tube 41 and the connecting portion 41c is referred to as the rear portion. The front portion of the plasma torch 40E has the same shapes and dimensions as a typical plasma torch, including the central tube 41, intermediate tube 42, and outer tube 43. In contrast, the rear portion of the plasma torch 40E has larger inner diameters of the central tube 41, intermediate tube 42, and outer tube 43 than a typical plasma torch.

[0095] Therefore, the inner diameter of the rear section 43b of the outer tube 43 is larger than the inner diameter of the front section 43f. Similarly, the inner diameter of the rear section 42b of the intermediate tube 42 is larger than the inner diameter of the front section 42f. Preferably, the front section 43f and the rear section 43b of the outer tube 43 are smoothly connected by an inverted cone-shaped connecting portion. Similarly, it is preferably that the front section 42f and the rear section 42b of the intermediate tube 42 are smoothly connected by an inverted cone-shaped connecting portion.

[0096] In the front portion of a typical plasma torch, the inner diameter of the outer tube is approximately 18 mm, the inner diameter of the intermediate tube is approximately 14 mm, and the inner diameter of the center tube is approximately 2.5 mm. In the rear portion of a typical plasma torch, the inner diameter of the outer tube is approximately 18 mm, the inner diameter of the intermediate tube is approximately 10 mm, and the inner diameter of the center tube is approximately 4 mm. In contrast, in the front portion of the plasma torch 40E of this embodiment, for example, the inner diameter of the outer tube 43 is 17 to 19 mm, the inner diameter of the intermediate tube 42 is 13 to 15 mm, and the inner diameter of the center tube 41 is 1 to 3 mm. In the rear portion of the plasma torch 40E, for example, the inner diameter of the outer tube 43 is 21 to 28 mm, the inner diameter of the intermediate tube 42 is 17 to 24 mm, and the inner diameter of the center tube 41 is 13 to 20 mm. If the thickness of the central tube 41 and the intermediate tube 42 is 1 mm and the thickness of the outer flow path and the intermediate flow path is 1 mm, the inner diameter of the outer tube 43 is 4 mm larger than the inner diameter of the intermediate tube 42, and the inner diameter of the intermediate tube 42 is 4 mm larger than the inner diameter of the central tube 41.

[0097] By increasing the inner diameters of the intermediate tube 42 and the outer tube 43 in the rear portion, the inner diameter of the body portion 41t of the central tube 41 is made larger than that of the fourth embodiment. Specifically, the inner diameter of the body portion 41t of the central tube 41 can be set to 13 mm or more. There is no particular upper limit to the inner diameter of the body portion 41t, but it can be increased to approximately 20 mm.

[0098] The plasma torch 40E of this embodiment has a larger inner diameter of the trunk portion 41t of the central tube 41, and therefore has a stronger desolvation function. Furthermore, because the shapes and dimensions of the front portion of the central tube 41, intermediate tube 42, and outer tube 43 are similar to those of a typical plasma torch, the plasma P can be stably maintained even if the gas flow rate, plasma output, and other conditions are set similarly to those of a typical plasma torch. No plasma torch has been reported to date in which the front and rear portions of the plasma torch have different functions and the shapes and dimensions are changed according to the functions.

[0099] The boundary between the front and rear sections of the plasma torch 40E can be set at any position. For example, as shown in FIG. 14, the boundary between the front and rear sections may be set midway along the trunk section 41t of the central tube 41. The inner diameter of the rear section 43b of the outer tube 43 is larger than the inner diameter of the front section 43f. Similarly, the inner diameter of the rear section 42b of the intermediate tube 42 is larger than the inner diameter of the front section 42f. Preferably, the front section 43f and the rear section 43b of the outer tube 43 are smoothly connected by a connecting portion having an inverted cone shape. Similarly, the front section 42f and the rear section 42b of the intermediate tube 42 are smoothly connected by a connecting portion having an inverted cone shape.

[0100] The front part of plasma torch 40E is similar to that of a general plasma torch in terms of the shape, inner diameter, and outer diameter of central tube 41, intermediate tube 42, and outer tube 43. Therefore, the front part of plasma torch 40E can be fixed using a torch installation stand (a stand for installing an outer tube with an outer diameter of 20 mm) that is generally used to hold and fix a plasma torch in an analyzer.

[0101] The trunk 41t of the central tube 41 has a large diameter in a portion corresponding to the rear portion. Specifically, the inner diameter of the portion of the trunk 41t of the central tube 41 can be made 13 mm or more. Since the inner diameter of the portion of the trunk 41t of the central tube 41 is large, the desolvation function can be improved.

[0102] The rear portion of the base end tube 44 is shaped to fit along the outer peripheral surface of the nebulizer 20E, and the front portion is shaped to fit along the inner peripheral surface of the central tube 41. The spray nozzle of the nebulizer 20E is located slightly forward of the base end tube 44. However, because the base end tube 44 causes the central tube sheath gas to flow along the inner peripheral surface of the central tube 41, the central tube sheath gas does not directly hit the spray nozzle of the nebulizer 20E.

[0103] The plasma torch 40E shown in Figure 14 is a demountable torch. That is, the central tube 41, intermediate tube 42, outer tube 43, and base tube 44 can be installed separately. In addition, branch tubes communicating with the nebulizer sheath gas flow path, central tube sheath gas flow path, auxiliary gas flow path, and plasma gas flow path are connected to a removable holder. A demountable torch has the advantage that if one tube is damaged or the water-repellent coating deteriorates, only that tube can be replaced. Instead of a demountable torch, a plasma torch with the central tube 41, intermediate tube 42, outer tube 43, base tube 44, and each branch tube integrated into one unit may be used.

[0104] Sixth Embodiment Next, a sample atomization and introduction device FF according to a sixth embodiment will be described. As shown in Figure 15, in the sample atomization and introduction device FF of this embodiment, the nebulizer 20F is directly connected to the plasma torch 40F. The plasma torch 40F has a triple-tube structure consisting of a central tube 41, an intermediate tube 42, and an outer tube 43. The plasma torch 40F also has a base tube 44. The nebulizer 20F is connected to the base tube 44 via a connector 50.

[0105] The central tube 41 of this embodiment comprises a base end 41e, a body 41t, and a nozzle 41n. A base tube 44 is inserted into the base end 41e. The base end 41e has a relatively large inner diameter, while the nozzle 41n has a relatively small inner diameter. The body 41t has an inverted cone shape, with the inner diameter continuously decreasing from the base end to the tip. The inner circumferential surface of the central tube 41 is a water-repellent surface 41r. Although not particularly limited, the lengths of the base end 41e, the body 41t, and the nozzle 41n are 5 to 20%, 65 to 85%, and 5 to 20%, respectively, of the total length of the central tube 41. The total length of the central tube 41 is 120 to 150 mm. It is not necessary for the entire central tube 41 to be inserted into the intermediate tube 42; only a portion of the central tube 41 is inserted into the intermediate tube 42.

[0106] If the central tube 41 has a shape in which the inner diameter does not change in the axial direction, the central tube sheath gas flow is maintained near the base end, which is effective in suppressing the adhesion of sample droplets. However, the sheath effect weakens near the tip, making the adhesion of sample droplets unavoidable. In contrast, in this embodiment, the body portion 41t, which accounts for most of the central tube 41, is in an inverted cone shape, so the central tube sheath gas flow is maintained all the way to the tip of the central tube 41, which is highly effective in suppressing the adhesion of sample droplets. In addition, the connection between the body portion 41t and the nozzle portion 41n is smooth, which reduces the adhesion of sample droplets to this area.

[0107] The inner circumferential surface of the connector 50 in this embodiment is shaped to fit the tip of the nebulizer 20F. In other words, the nebulizer sheath gas flow path 51 is thin throughout the entire tip of the nebulizer 20F. Therefore, even if the flow rate of the nebulizer sheath gas is reduced, the flow rate can be maintained, and adhesion of sample droplets to the outer circumferential surface of the nebulizer 20F can be suppressed. Adhesion of sample droplets can be effectively suppressed even if the outer circumferential surface of the tip of the nebulizer 20F is not made water-repellent.

[0108] Seventh Embodiment Next, a sample atomization and introduction device GG according to a seventh embodiment will be described. As shown in FIG. 16, the plasma torch 40G of this embodiment, like the plasma torch 40F of the sixth embodiment, has a central tube 41 that includes a base end 41e, a trunk 41t, and a nozzle 41n. However, the trunk 41t includes a rear portion 41b on the base end 41e side and a front portion 41f on the nozzle 41n side. The joint between the rear portion 41b and the front portion 41f is called an intermediate portion. The rear portion 41b has a cone shape in which the inner diameter increases continuously from the base end toward the intermediate portion. The front portion 41f has an inverted cone shape in which the inner diameter decreases continuously from the intermediate portion toward the tip. Although not particularly limited, the lengths of the rear portion 41b and the front portion 41f are 5 to 15% and 85 to 95% of the total length of the trunk 41t, respectively. It is preferable that the rear portion 41b and the front portion 41f be smoothly connected.

[0109] The sample droplets sprayed from the nebulizer 20G spread in a cone shape. Because the spread of the sample droplets is small near the spray nozzle of the nebulizer 20G, the sample droplets are less likely to adhere even if the inner diameter of the central tube 41 is small. Conversely, if the inner diameter of the central tube 41 is too large, dead volume will be created, causing delays in the rise and fall of the signal peak. In this embodiment, the rear portion 41b of the central tube 41 is cone-shaped to match the spread of the sample droplets sprayed from the nebulizer 20G, resulting in less dead volume and enabling quick rise and fall of the signal peak.

[0110] It is preferable that the front end of the base end tube 44 has a shape that widens along the inner circumferential surface of the rear portion 41b of the central tube 41. In this way, a central tube sheath gas flow can be formed along the inner circumferential surface of the central tube 41.

[0111] Eighth Embodiment Next, a sample atomization and introduction device HH according to an eighth embodiment will be described. As shown in Figure 17, in the sample atomization and introduction device HH of this embodiment, a nebulizer 20H is directly coupled to a plasma torch 40H. A micro-flow nebulizer is used as the nebulizer 20H. Meanwhile, the sample supply source 10H uses a pump, pump tube, and liquid supply tube that are used in a normal sample supply source. The sample atomization and introduction device HH of this embodiment is capable of supplying a liquid sample at a flow rate suitable for the micro-flow nebulizer 20H, while using the pump, pump tube, and liquid supply tube that are used in a normal sample supply source.

[0112] In a typical sample supply source, the pump tube and liquid delivery tube have large inner diameters, resulting in a large total volume. If the liquid is delivered at a flow rate suitable for a microflow nebulizer, it takes a long time for the liquid sample to reach the microflow nebulizer, preventing rapid analysis. For example, if the total volume of the tubing is 0.3 mL and the delivery flow rate to the microflow nebulizer is 0.03 mL / min, it will take 10 minutes for the liquid sample to reach the microflow nebulizer.

[0113] Therefore, the sample supply source 10H of this embodiment includes a container 11 for storing a liquid sample, a flexible tube 12, a pump 13 provided midway along the tube 12, and a splitter 17. The pump 13 delivers the liquid sample from the container 11 at a normal delivery rate to the splitter 17. The splitter 17 delivers a portion of the liquid sample delivered from the pump 13 to the nebulizer 20H and discharges the remainder. For example, the pump 13 delivers the liquid sample at 0.6 mL / min, and the splitter 17 delivers the liquid sample to the nebulizer 20H at 0.03 mL / min and discharges it at 0.57 mL / min.

[0114] For example, if the pump 13's liquid delivery rate is set to 0.6 mL / min, the time it takes for the liquid sample to reach the microflow nebulizer can be shortened to 0.5 minutes. At the same time, the liquid sample can be supplied to the nebulizer 20H at a flow rate appropriate for the liquid sample. Because the splitter 17 allows the liquid sample to be supplied to the nebulizer 20H at a flow rate appropriate for the liquid sample, the pump 13's liquid delivery rate can be increased to shorten the time it takes for the sample solution to reach the nebulizer. [Example]

[0115] Example 1 A liquid sample was atomized using the sample atomization and introduction device DD configured as shown in Figures 11 and 12 to generate sample droplets, which were then introduced into an ICP mass spectrometer. A microflow nebulizer was used as the nebulizer 20D. The body 41t of the central tube 41 of the plasma torch 40D had an inner diameter of 10 mm and a length of 72 mm. The inner surface of the central tube 41 was not water-repellent. A 2% nitric acid solution with a mercury concentration of 5 μg / L was used as the liquid sample. The liquid sample was introduced into the nebulizer 20D at a flow rate of 0.02 mL / min for approximately 2 minutes. The central tube sheath gas was also flowed at a flow rate of 0.5 L / min. The output results of the analyzer at this time are shown in Figure 18(A).

[0116] (Comparative Example 1) A liquid sample was atomized using the sample atomization and introduction device shown in Figure 1 to generate sample droplets, which were then introduced into an ICP mass spectrometer. The plasma torch used was a commonly used one, with the central tube having an inner diameter of 4 mm and a length of 68 mm. A 2% nitric acid solution with a mercury concentration of 5 μg / L was used as the liquid sample. The liquid sample was introduced into the nebulizer at a flow rate of 1 mL / min for approximately 2 minutes. The output results from the analyzer at this time are shown in Figure 18(B).

[0117] The vertical axes of the graphs shown in Figures 18(A) and 18(B) are logarithmic. In both Example 1 and Comparative Example 1, a 2% nitric acid solution is introduced into the plasma from 0 seconds to approximately 60 seconds. The signal intensity obtained at this time is taken as the background level. At approximately 60 seconds, mercury is introduced into the plasma, and the signal intensity increases rapidly. Thereafter, the signal intensity remains constant from approximately 60 seconds to approximately 180 seconds. At approximately 180 seconds, the solution is switched back to 2% nitric acid, and the signal intensity decreases toward the background level. Note that once the signal intensity returns to the background level, analysis of the next sample is possible.

[0118] In Example 1 (FIG. 18(A)), the signal intensity returns to the background level at approximately 380 seconds, which is approximately 200 seconds after the signal intensity began to decrease. On the other hand, in Comparative Example 1 (FIG. 18(B)), the signal intensity has not returned to the background level even at 840 seconds, which is approximately 660 seconds after the signal intensity began to decrease. This confirms that the time required for the signal intensity to return to the background level is shorter in Example 1 than in Comparative Example 1. This means that samples can be analyzed in short time intervals in Example 1.

[0119] Furthermore, from the perspective of sensitivity, the absolute amount of mercury sprayed by the nebulizer was 0.2 ng in Example 1 and 10 ng in Comparative Example 1, a 50-fold difference, yet the signal intensity obtained in both cases was nearly the same. In Comparative Example 1, most of the sample droplets sprayed by the nebulizer collided with the wall of the spray chamber, so only about 2% of the droplets reached the plasma. In contrast, in Example 1, almost all of the sample droplets sprayed by the nebulizer were introduced into the plasma. Thus, Example 1 exhibited high sample droplet transport efficiency to the plasma, improving the sensitivity of the analytical device.

[0120] Example 2 A liquid sample and a 2% nitric acid solution were sprayed alternately for two hours continuously into a sample atomization introduction device DD having the same configuration as in Example 1. After that, when the inner peripheral surface of the central tube 41 of the plasma torch 40D was observed, no adhesion of liquid droplets was observed.

[0121] (Comparative Example 2) A minute flow rate nebulizer was directly connected to the base of a plasma torch having the same configuration as in Comparative Example 1, and droplets were sprayed. As a result, adhesion of droplets to the inner surface of the central tube of the plasma torch was observed immediately after spraying.

[0122] This confirms that, compared to Comparative Example 2, the configuration of Example 2 can suppress the adhesion of sample droplets to the inner peripheral surface of the central tube 41 of the plasma torch 40D.

[0123] As described above, it was confirmed that by making the inner diameter of the body of the central tube of the plasma torch 10 mm or more and flowing central tube sheath gas, it is possible to suppress the adhesion of sample droplets and to suppress the memory effect, even without making the inner surface of the central tube water-repellent. [Explanation of symbols]

[0124] AA, BB, CC, DD, EE, FF, GG, HH sample atomization introduction device 20A, 20D, 20E, 20F, 20G, 20H Nebulizer 20r water repellent surface 40A, 40B, 40C, 40D, 40E, 40F, 40G, 40H Plasma Torch 41 Central canal 41r water repellent surface 42 Intermediate tube 43 Outer tube 44 Proximal tube 44r water repellent surface 48 Gas inlet

Claims

1. A sample atomization and introduction device that atomizes a liquid sample and introduces the atomized sample droplets into a sample introduction portion of an analytical device, All or part of the wall surface constituting the flow path for the sample droplet is a water-repellent surface that has been subjected to a water-repellent treatment. A sample atomization and introduction device characterized by the above.

2. The water-repellent surface is a surface that has been subjected to lining processing with a fluorine-based resin, coating processing with a fluorine-based compound, coating processing with a silicone-based compound, or nano-micro structure formation processing.

2. The sample atomization and introduction device according to claim 1.

3. The water-repellent surface has a contact angle with water of 150° or more.

2. The sample atomization and introduction device according to claim 1.

4. a nebulizer that atomizes the liquid sample to spray the sample droplets; a nebulizer sheath gas flow path that allows a nebulizer sheath gas to flow along an outer peripheral surface of the tip of the nebulizer; The outer peripheral surface of the tip of the nebulizer is the water-repellent surface.

2. The sample atomization and introduction device according to claim 1.

5. Equipped with a plasma torch, The plasma torch is a central tube through which the sample droplets flow; an intermediate tube into which the central tube is inserted and through which an auxiliary gas flows between the intermediate tube and the central tube; an outer tube into which the intermediate tube is inserted and through which plasma gas flows between the outer tube and the intermediate tube; 2. The sample atomization and introduction device according to claim 1.

6. The inner peripheral surface of the central tube is the water-repellent surface.

6. The sample atomization and introduction device according to claim 5.

7. The plasma torch further includes a base end tube inserted into the base end of the central tube, through which a central tube sheath gas flows between the base end tube and the central tube.

6. The sample atomization and introduction device according to claim 5.

8. The inner peripheral surface of the base end tube is the water-repellent surface.

8. The sample atomization and introduction device according to claim 7.

9. a nebulizer that atomizes the liquid sample to spray the sample droplets; The spray nozzle of the nebulizer is disposed inside the proximal tube.

8. The sample atomization and introduction device according to claim 7.

10. The central tube has a gas inlet for introducing a portion of the auxiliary gas into the central tube to flow as a central tube sheath gas.

6. The sample atomization and introduction device according to claim 5.

11. The central tube has a body with an inner diameter of 10 mm or more. The sample atomization and introduction device according to any one of claims 7 to 10.

12. the outer tube has a larger inner diameter at its rear portion than at its front portion; the intermediate tube has a rear portion with a larger inner diameter than a front portion; The central tube has a body with an inner diameter of 13 mm or more.

6. The sample atomization and introduction device according to claim 5.

13. The central tube has an inverted cone-shaped body whose inner diameter continuously decreases from the base end to the tip end.

6. The sample atomization and introduction device according to claim 5.

14. The central tube has a body portion consisting of a cone-shaped rear portion whose inner diameter increases continuously from the base end to the middle portion, and an inverted cone-shaped front portion whose inner diameter decreases continuously from the middle portion to the tip.

6. The sample atomization and introduction device according to claim 5.

15. A heater is provided for heating the central tube sheath gas introduced into the central tube.

6. The sample atomization and introduction device according to claim 5.

16. a nebulizer that atomizes the liquid sample to spray the sample droplets; a nebulizer sheath gas flow path that allows a nebulizer sheath gas to flow along an outer peripheral surface of the tip of the nebulizer; a humidifier for humidifying the nebulizer sheath gas.

2. The sample atomization and introduction device according to claim 1.

17. a pump for delivering the liquid sample; a splitter that supplies a portion of the liquid sample delivered from the pump to a nebulizer and discharges the remainder.

2. The sample atomization and introduction device according to claim 1.

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