JP2008275372A - Plasma analyzer and plasma analysis method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new device and a method suitable for diluting a high matrix solution sample before changing it to plasma. <P>SOLUTION: A current by additional gas G2 is provided in the middle of a transport pipe 70 elongated from a spray chamber 20 and connected to a plasma torch 30. Though an atomized analysis sample is moved from the spray chamber 20 to the plasma torch through the transport pipe 70 by gas G1 introduced into the spray chamber 20, movement is disturbed by existence of the current of the additional gas G2 crossing to the moving direction. In this case, liquid particles constituting mist are bonded mutually into particles having a comparatively large size, to thereby form liquid drops on a wall surface in the middle of the transport pipe 70. Hereby, the amount of the sample reaching the plasma torch 30 can be controlled and reduced with excellent repeatability. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a technique of a plasma analysis apparatus or a plasma analysis method for performing quantitative analysis of elements using plasma.

  A chemical analysis method for analyzing mainly inorganic elements by an analysis method using plasma is conventionally known. According to this technique, plasma is generated in a plasma torch using a gas such as argon, and the sample to be analyzed is fed into the plasma. In one method, light emission generated in the plasma is analyzed, and in another method, ions are extracted from the generated plasma, and mass analysis of the ions is performed. These methods are widely used as plasma emission analysis and plasma mass spectrometry, respectively. As an energy source for generating plasma, for example, a high-frequency electromagnetic field is used.

  An inductively coupled plasma mass spectrometer (ICP-MS) is known as an analyzer by plasma mass spectrometry. In this apparatus, first, an analysis sample, which is often a liquid, is made into a mist in the former part and put into plasma. In the latter part, a part of the plasma is extracted in the form of an ion beam, the extracted ions are separated by the mass-to-charge ratio, this is detected, and the element is identified from the output.

  More specifically, the front part of the apparatus includes sample preparing means for taking out a liquid sample and a spray chamber for atomizing the prepared liquid sample. The sample preparation means includes a suction pipe for sucking the liquid sample from the sample container, and if necessary, a liquid feeding means is provided in a part of the suction pipe. According to one application, the liquid sample and the other solution can be mixed at a predetermined ratio by controlling a plurality of combined liquid feeding means, and thus the concentration of the solution can be changed. Typically, a peristaltic pump is used as the liquid feeding means (Patent Document 1).

  The spray chamber includes a nebulizer that converts a liquid sample into a small-diameter liquid droplet form using a predetermined flow rate of gas according to the principle of spraying. A large number of liquid particles generated by the nebulizer are classified as they pass through the space in the spray chamber. That is, liquid particles having a relatively large particle size remain in the spray chamber and adhere to the inner surface, and flow downward to be drained. On the other hand, liquid particles having a relatively small particle diameter are discharged from the spray chamber in the form of mist or aerosol together with the gas introduced into the spray chamber. The gas introduced into the spray chamber includes the gas used for spraying in the nebulizer and the gas introduced at another position in the spray chamber as necessary.

The liquid droplets of the analysis sample discharged from the spray chamber are guided to the plasma torch via the transport pipe. In the plasma torch, plasma is generated in advance by a gas such as argon, and the liquid particles of the analysis sample are put into the plasma and ionized. The sheath gas may be introduced in the middle of the transport pipe before the liquid droplet of the analysis sample is put into the plasma torch. The sheath gas is for facilitating the flow of liquid particles inside the transport pipe. For introducing the sheath gas, a double-structure tube is usually used (Patent Document 2).
Japanese Patent Laid-Open No. 11-6788 JP-A-6-102249

  One sample expected to be easily analyzed with this type of apparatus is a high matrix solution sample. The high matrix sample refers to a sample containing a high concentration metal salt or other water-soluble substance in addition to the element to be measured. As a technique for analyzing a high matrix sample, for example, as described above, the sample solution may be mixed with another solution or solvent in a liquid state to reduce the concentration of the matrix element.

  However, according to such a method, there is a possibility that other elements may be mixed in the treatment of the solution, which is not preferable for analysis of trace elements. In addition, the solution mixing process requires an additional device, which increases the overall time required for the analysis operation. Therefore, it is preferable that the solution containing the matrix element at a high concentration can be directly input into the apparatus for analysis.

  The main problem when a high matrix sample is used as an analysis sample is that it contaminates each element for taking out or controlling the ion beam located at the subsequent stage of the above-described apparatus and adversely affects the analysis. Specifically, the following points are cited as problems.

  First, the latter part of the device is provided with interface elements (sampling cone and skimmer cone) with orifices for passing the ion beam facing the plasma, but with a high matrix sample, When the plasma is generated without lowering, the matrix element may adhere to the interface element and block the orifice. In such a case, ions cannot pass through the interface and cannot be analyzed. Even if it does not go down, there is a possibility that the attached matrix element reduces the opening diameter of the orifice, and the sensitivity is very low, so that the analysis cannot be performed.

  Secondly, the matrix elements that enter the latter part of the apparatus adhere to the interface and other elements and contaminate the vacuum chamber. The matrix elements attached to each element are subjected to the next analysis following the analysis. Can cause noise. Therefore, it is necessary to clean the inside of the apparatus after analytical measurement of a high matrix sample. As a result, it takes time for maintenance work for disassembling, cleaning, and assembling the apparatus, and extra time is required.

  Third, in the case of a sample with a particularly high matrix concentration, the matrix element also adheres to the plasma torch. That is, the matrix element is deposited so as to close the inner tube at the end of the plasma torch on the plasma generation side. As a result, the sample introduced into the plasma may become too small and analysis may not be possible. In addition, it is necessary to replace or clean the plasma torch before performing the next analysis.

  Therefore, the above problem can be solved if the matrix concentration of the high matrix sample can be effectively lowered before the sample is taken out as a solution and then converted into plasma. That is, a first object of the present invention is to provide an apparatus including a novel diluting means for effectively lowering the matrix concentration of a high matrix sample that is a solution before being converted to plasma, and an operation method thereof. .

  The second object of the present invention is to control the degree to which the matrix concentration of a high matrix sample is lowered, that is, the degree of dilution, with good reproducibility in the above case.

  In the present invention, an additional gas flow is provided in the middle of the transport tube extending from the spray chamber and connected to the plasma torch. As described above, the analysis sample atomized in the spray chamber is carried by the gas introduced into the spray chamber so as to move to the plasma torch in the transport tube, but intersects the moving direction of the analysis sample. The movement is hindered by the flow of additional gas flowing in the direction. When obstructed, the liquid particles constituting the mist combine with each other to form particles having a relatively large diameter and form droplets on the wall surface in the middle of the transport pipe. As a result, the liquid particles containing the analysis sample reaching the plasma torch are reduced, and the amount of matrix elements and other elements that are converted into plasma by the plasma torch is reduced.

  That is, the present invention provides a spray chamber for atomizing a solution as an analysis sample by spraying using at least a part of the introduced first gas, and transport for transporting the atomized analysis sample together with the first gas. A plasma analysis apparatus including a plasma generating means including a tube and a plasma torch connected to the transport tube and introducing the analysis sample transported through the transport tube into the plasma, and in particular, the first gas is An unreacted second gas (that is, an additional gas) is introduced so as to generate an air flow from one side of the inner surface of the transport pipe to the opposite surface at an intermediate position in the length direction of the transport pipe, and the presence of the air flow A plasma analysis apparatus is provided in which a part of the analysis sample atomized by the method is changed into a droplet at an intermediate position to reduce the total amount of the analysis sample reaching the plasma torch.

  Furthermore, the present invention includes a step of sucking an analysis sample that is a liquid from a sample container, and spraying the sucked analysis sample using at least a part of the first gas introduced into the spray chamber, so that a mist is sprayed into the spray chamber. Generating the atomized analysis sample, transporting the atomized analysis sample together with the first gas to the plasma torch, and bringing the analysis sample atomized by the plasma torch into a plasma state; A plasma analysis method including the step of detecting the emission of plasma or ions extracted from the plasma and identifying the element, and in particular, the step of introducing the atomized analysis sample to the plasma torch is a first step. A second gas that does not react with the gas, that is, an additional gas, is introduced at an intermediate position in the length direction of the transport pipe so as to generate an air flow from one side surface of the transport pipe toward the opposite surface. The plasma includes a step of reducing a total amount of the analysis sample reaching the plasma torch by changing a part of the analysis sample atomized by the airflow into a droplet at an intermediate position and attaching it to the inner surface of the transport tube. Provide analytical methods.

  The additional gas introduced after the spray chamber may be the same type of gas as that introduced into the spray chamber. For example, both of them may be argon gas. In other cases, the first gas may be argon gas and the second gas may be oxygen gas. By controlling the flow rate of the additional gas, operation with good reproducibility can be guaranteed. Additional gas may be introduced from the small tube section, which is a small diameter tube, to form a jet or jet. In this case, the flow rate at which additional gas is introduced may be set to be at least 50 times greater than the flow rate of the gas exhausted from the spray chamber and moving through the transport tube and, depending on conditions, greater than 100 times. The small pipe portion may be formed integrally with the transport pipe or may be a single part. In any case, the flow rate of the additional gas in the small tube portion can be increased by connecting the small tube portion to the tip of the relatively large diameter tube.

  The transport pipe may include a rising portion that extends upward in the height direction from the spray chamber, and the small pipe portion that introduces additional gas may be configured to be connected to the rising portion. At this time, the droplet flows and moves on the inner surface of the transport pipe so as to return from the rising portion into the spray chamber by gravity.

  In this case, at least a part of the inner surface of the transport pipe from the position where the additional gas is introduced to the spray chamber can be provided with a surface portion having a property that droplets do not remain. The surface portion may include a portion that has been treated to enhance hydrophilicity or water repellency (hydrophobicity). For example, the surface portion may be composed of an inner surface processed into a frosted glass shape to enhance hydrophilicity, or may be composed of a coating film coated on the inner surface to enhance hydrophilicity or water repellency. In other cases, a part including the surface portion may constitute a part of the transport pipe.

  The rising portion may be provided with cleaning means that operate in a timely manner to assist the droplets in returning to the spray chamber. For example, the cleaning means can be a means for providing a liquid flow or a gas flow that flows from the midpoint of the rising portion toward the spray chamber.

  The rising portion does not extend in the vertical direction from the spray chamber, but may be inclined, but it is preferable to form an angle of 45 degrees or more from the horizontal plane in order to smoothly move the droplet. .

  On the other hand, the small pipe portion can be connected to the transport pipe in such a direction that the direction of introduction of the additional gas forms a right angle or an obtuse angle with respect to the direction in which the analysis sample atomized in the transport pipe is transported. Moreover, the said small pipe part may be comprised from the tubular member separate from a transport pipe.

  The plasma analyzer may have a controller for controlling the flow rate of the additional gas. Together, the control device can control the flow rate of the gas introduced into the spray chamber. That is, in this case, the control device can control the total flow rate of the gas introduced into the spray chamber and the additional gas and the ratio of both.

  By introducing an additional gas (ie, a second gas) that flows across the transport tube, a portion of the atomized analytical sample is converted into droplets along the transport tube, thereby reaching the plasma torch. Since the amount of liquid particles containing the analysis sample can be effectively reduced, even if the analysis sample is a high matrix sample, the analysis work can be performed continuously without the need for other special dilution means. It can be carried out. In addition, by controlling the amount of additional gas introduced, the degree of dilution, that is, the amount of droplets generated can be controlled, thereby enabling reproducible analysis.

  Furthermore, the present invention effectively converts the analysis sample into droplets even with a relatively small amount of gas introduction so that additional gas is introduced across the transport tube, preferably in the form of a jet. Can do. In other words, when the total flow rate of the gas introduced into the spray chamber and the additional gas is determined, it is not necessary to excessively reduce the flow rate of the former gas. This is advantageous in that the degree of freedom in selecting the type of nebulizer used when spraying the analysis sample is increased, and the stable operation of the nebulizer can be ensured.

  Exemplary embodiments of a plasma analysis apparatus and a plasma analysis method according to the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram mainly showing plasma generation means provided in the previous stage for generating plasma in the configuration of the inductively coupled plasma mass spectrometer according to the embodiment of the present invention. The plasma generating means has a spray chamber 20 that atomizes by spraying and classifying the sample solution 41, and a plasma torch 30 that takes the atomized sample transported from the spray chamber 20 into the plasma. The spray chamber 20 and the plasma torch 30 are connected via a transport pipe 70 for transporting the atomized sample.

  Immediately after the plasma generating means, an interface 50 that constitutes a part of the mass analyzer is arranged. The interface 50 includes a sampling cone 51 and a skimmer cone 52, and plays a role of extracting an ion beam from the generated plasma. The extracted ion beam is separated based on the mass-to-charge ratio by a separation unit (not shown), and further detected by a detection unit at a later stage.

  On the other hand, a sample container 40 is connected to the front stage of the plasma generating means, that is, the front stage of the spray chamber 20. In the sample container 40, an analysis sample 41, which is typically a liquid, is placed. As the analysis sample 41, solutions having various matrix concentrations are prepared. Although only a single container is shown in FIG. 1, a plurality of sample containers 40 can be prepared for continuous analysis or solution mixing.

  A sample suction means 42 is coupled to the sample container 40. The analysis sample 41 in the sample container 40 is guided to the spray chamber 20 by the sample suction means 42. The sample suction means 42 is composed of a glass tube, a resin tube, a metal pipe with or without a fused silica coating inside, and the like. Regarding the resin tube, as the resin constituting the tube, for example, a fluorine-based resin, a peak resin (registered trademark “PEEK”) or the like is used. Depending on the application, a peristaltic pump can be provided for liquid delivery. The peristaltic pump is installed in a resin tube portion constituting a part of the sample suction means 42.

  A sample guided from the sample container 40 is put into a sample inlet 61 of a nebulizer 60 coupled to the spray chamber body 21. In the nebulizer 60, a gas G <b> 1 that forms an air flow that is generally parallel to the flow of the sample is further introduced from the gas inlet 62. The gas G1 is an inert gas such as argon gas. As shown in the drawing, at the tip of the nebulizer 60, the gas G1 and the liquid sample are discharged into the spray chamber body 21 from a close position. At this time, the spraying action of the sample is caused by the principle of spraying, and the liquid sample is changed into a liquid particle form.

  The sprayed liquid sample constitutes liquid particles of various diameters. Among these, the relatively large-diameter heavy liquid particles adhere to the inner surface of the spray chamber body 21, move downward along the inner surface by gravity, and are discharged from the drain 22. The light liquid particles having a relatively small diameter are carried by the gas flow in the chamber space 23 so as to circulate, and a part thereof is guided to the transport pipe 70. In FIG. 1, the gas G <b> 1 introduced into the spray chamber 20 is shown to be provided only to the nebulizer 60, but in addition to that, the gas G <b> 1 is introduced directly into the spray chamber body 21 without going through the nebulizer 60. Gas G1 can also be included. In FIG. 1, the spray chamber is shown as a Scott type (double pass type), but the present invention can be applied to other types of spray chambers such as a cyclone type. The flow rate of the gas G1 introduced into the spray chamber can be controlled by the gas flow rate controller 90 together with the flow rate of the additional gas G2 described later.

  Further, as shown in FIG. 1, the transport pipe 70 is substantially L-shaped, and includes a rising portion 71 extending upward from the spray chamber 20 and a horizontal portion 72 extending horizontally toward the plasma torch 30. Have. In the example of FIG. 1, the angle α in the drawing is approximately 90 degrees, and the rising portion extends in a substantially vertical direction. The atomized sample is carried by the gas flow flowing in the transport pipe 70, passes through the rising portion 71 and the horizontal portion 72, and is guided to the plasma torch 30. The inner diameters of the rising portion 71 and the horizontal portion 72 are not necessarily the same. Further, in the drawing, the transport pipe 70 is shown continuously with the spray chamber 20 and an inner pipe 32 of the plasma torch 30 described later, but is typically prepared as a separate body and coupled thereto. used. In this embodiment, the horizontal component 72 is shown in order to illustrate the present invention by showing an inductively coupled plasma mass spectrometer, but the present invention is also applicable to an upright plasma torch used in a plasma spectrometer. Can be applied.

  The plasma torch 30 has a triple tube configuration including an inner tube 32, an outer tube 33, and an outermost tube 34. The inner tube 32 is for introducing a sample, and the inner tube 32 and the outer tube 33 are for supplying plasma gas and auxiliary gas, respectively. First, a plasma gas and an auxiliary gas are passed through the plasma torch 30, and a high-frequency electromagnetic field is provided by a coil 31 connected to a high-frequency power source (not shown) in that state. Thereby, plasma (refer to the broken line P) can be generated on the plasma torch 30.

  The atomized analysis sample is introduced into the plasma through the inner tube 32 after the generation of the plasma. Thereby, the element which comprises a sample becomes a form of ion in plasma. As described above, a part of the plasma containing ions of the analysis sample constituent elements is led to the subsequent mass analysis unit (not shown) via the interface 50.

  The main feature of the present invention lies in the configuration and operation of the transport pipe 70, which is shown as a broken line portion A in FIG. The first feature is that the small-diameter small pipe portion 80 is coupled in the direction intersecting at the midway position of the transport pipe 70, and the gas G2 is introduced from the small pipe portion 80 at a predetermined flow rate. As a result, a part of the atomized analysis sample in the transport tube 70 toward the plasma torch 30 is changed into a relatively large droplet and adheres to the inner surface of the transport tube 70. As a result As a result, the amount of analysis sample reaching the plasma torch 30 can be intentionally reduced.

  The second feature is that the connecting position of the small tube portion 80 is a midway position of the rising portion 71. As a result, the droplets adhering to the inner surface of the rising portion of the transport pipe 70 flow downward and return to the spray chamber 20 by the action of gravity.

  FIG. 2 is a schematic view schematically showing the action of the gas introduced from the small pipe portion, which is a feature of the present invention. These characteristic configurations and operations will be further described in detail with reference to FIG. As shown in FIG. 2, an additional gas G <b> 2 is introduced through the small pipe portion 80. The diameter of the small pipe portion 80 is set sufficiently smaller than the diameter of the transport pipe 70 in the rising portion 71. For example, when the diameter of the transport pipe 70 in the rising portion 71 is 5.5 millimeters, the diameter of the small pipe portion 80 can be 0.3 millimeters to 0.5 millimeters.

  Since the diameter of the small pipe portion 80 is relatively small, the gas flow F <b> 2 flowing from the small pipe portion 80 into the transport pipe 71 has a relatively high flow velocity and flows so as to cross the transport pipe 70. In many cases, the gas stream F2 forms a gas jet or jet. As a result, a part of the atomized sample flowing so as to rise in the rising portion 71 of the transport pipe 70 by the gas flow F1 tends to be collected particularly toward the inner surface 78 on the opposite side. In the vicinity of the inner surface 78, the distance between the liquid droplets is reduced, and some of the liquid particles are bonded to each other to grow into a liquid particle having a larger diameter. Due to such a phenomenon, a part of the liquid droplets of the atomized sample is trapped in the middle of the transport tube 70, and the amount of the sample passing through the position of the small tube part 80 and going upward is reduced.

  Further, as illustrated or described above, the small pipe portion 80 is provided at the rising portion 71 of the transport pipe 70 extending in the substantially vertical direction. The droplet 45 generated in the above-described process flows downward along the inner surface 78 by the action of gravity, that is, in a direction returning to the spray chamber 20 (see arrow B). The cross section of the internal space of the rising portion 71 has a relatively small diameter (about 5 to 6 millimeters), and if the droplet 45 stays in the rising portion 71 in a large amount, sufficient analysis sensitivity cannot be obtained, or the tube is blocked. It may be impossible to analyze. Such an adverse effect is prevented by the above-described action of removing the droplet by gravity.

  In this case, it is preferable to provide a surface portion 73 having high hydrophilicity or water repellency on at least a part of the inner surface 78 of the rising portion 71 of the transport pipe 70 so that the droplet 45 can move downward smoothly.

  Specifically, the surface portion 73 can be an inner surface processed into a ground glass shape so as to enhance hydrophilicity. In other cases, the surface portion 73 may include a coating film provided on the inner surface 78 to enhance hydrophilicity or hydrophobicity. Further, in other cases, the surface portion uses a part constituting at least a part of the length of the transport pipe 70, and the inner side surface is made of a material having a high hydrophilicity or water repellency. good. 1 and 2, the surface portion 73 is shown only on the inner surface on the side facing the small tube portion 80. However, any surface that forms a part of the flow path when a droplet adheres and flows downward is shown. About the side surface, a surface portion 73 having high hydrophilicity or water repellency can be provided.

  FIG. 3 is a schematic cross-sectional view showing a configuration example of the small tube portion. In the example of FIG. 3A, the small pipe portion 80a is formed integrally with the transport pipe 70, or is connected to the transport pipe 70 as a separate body. As shown in the figure, in this example, the small tube portion 80a is formed continuously with the large tube portion 81 having a relatively large diameter. By adopting such a configuration, it is possible to realize a gas flow having a high flow velocity flowing in the small pipe portion 80a by a relatively simple method.

  In the example of FIG. 3B, the small pipe portion 80 b is a separate part from the transport pipe 70 and is disposed in an opening 82 provided in the transport pipe 70. The tip of the small pipe portion 80b can be terminated at a position aligned with the inner surface of the transport pipe 70 as shown by a solid line, but enters the transport pipe 70 as shown by a broken line 84 (for example, 1/1 of the diameter). 4 to 1/2 size). The small pipe portion 80b is supported in a state of being sealed by a seal member 83 such as a ring component in the opening 82. Such a configuration facilitates the manufacture of parts constituting the small pipe portion 80b and the handling for assembly.

  In the example of FIG. 3C, the small pipe portion 80 c is installed so as to be inclined at a predetermined angle, not in a direction orthogonal to the transport pipe 70. In order to obstruct the flow of the atomized sample in the transport tube 70 and effectively generate droplets, the angle β becomes an acute angle (that is, the small tube portion 80c introduces the additional gas G2). It is preferable that the direction is coupled to the transport pipe 70 in such a direction that an obtuse angle is formed with respect to the direction in which the analysis sample atomized in the transport pipe 70 is transported.

  Note that the examples in FIGS. 3A to 3C are not independent of each other, and can be realized as a configuration combined with each other. For example, as shown in FIG. 3A, a small tube portion 80a extending beyond the large-diameter portion 81 can be held by the seal member 83 as the small tube portion 80b in FIG. 3B.

  FIG. 4 is a view showing a modified example of the transport pipe. In the transport pipe 170 shown in FIG. 4, the rising portion 171 extends not in the vertical direction but in an inclined direction with respect to the horizontal portion 172 extending horizontally toward the plasma torch. A droplet generated on the same principle as the above example moves downward along the inclined inner surface by gravity (see arrow B '). The above-described surface portion 173 having high hydrophilicity or high water repellency can be formed on the entire inner surface serving as a flow path through which droplets flow at least when gravity acts. The angle α ′ in the figure should be selected in consideration of the properties of the surface portion 173 and the like, but is preferably smaller than 135 degrees (that is, the rising portion is an angle of 45 degrees or more from the horizontal plane). Can be determined).

  FIG. 5 is a diagram showing a further modification of the rising portion of the transport pipe. In contrast to FIG. 1, elements that act in the same way are denoted by reference numerals 200 and description thereof is omitted. The feature of this example is that a step 275 is provided in the middle of the rising portion 271. That is, in this example, the rising portion 271 extends in a downwardly inclined manner continuously from the upper tube portion 274 having a relatively small diameter located at the upper portion, a step portion 275 provided to spread outward at the lower end thereof, and the step portion 275. An inclined portion 276 and a lower pipe portion 277 that has a relatively large diameter and continues to the spray chamber 220 are included.

  As illustrated, the step portion 275, the inclined portion 276, and the lower tube portion 277 constitute a small chamber 279 in the rising portion 271. The small tube portion 280 is coupled to the small chamber 279 in the vicinity of the inclined portion 276. The airflow by the gas G2 introduced from the small pipe portion 280 moves so as to cross the small chamber 279. By providing the stepped portion 275, the droplet blown by the air current is prevented from moving to the upper tube portion 274, and as a result, the generated droplet moves downward.

  In this example, as in the above-described example, the droplets are generated along the inner surface of the transport pipe chamber 279, that is, along the inner surface of the inclined portion 276 or the lower tube portion 277, and then downward along those inner surfaces. Will be moved to. Therefore, it is preferable to provide a surface portion 273 having high hydrophilicity or water repellency along the flow path.

  FIG. 6 is a diagram illustrating a modified example in which a cleaning unit is provided in order to ensure that no droplets stay. In contrast to FIG. 1, elements that act in the same way are denoted by reference numerals 300 and description thereof is omitted. The cleaning means is indicated by reference numeral 391. CF in the figure indicates a fluid such as gas or liquid used for cleaning.

  The cleaning means 391 supplies a gas flow or a liquid flow for cleaning the inside of the pipe into the rising portion 371 at a predetermined timing such as after the analysis of a predetermined sample is completed. Droplets adhering to the inner surface of the rising portion 371 are washed and discharged from the drain 322 through the spray chamber 320. As a result, the hydrophilic or water-repellent state of the inner surface of the rising portion 371 is maintained, and the droplet can effectively flow down during the subsequent analysis.

  FIG. 7 is a graph illustrating the effects of the apparatus or method according to the present invention. Two types of experimental data are shown for comparison. In the figure, D1 indicates a dilution action by the additional gas having a relatively high flow rate, and D2 indicates a dilution action by the additional gas having a relatively low flow rate. More specifically, D1 shows a case where the diameter of the small pipe portion is made small so that the flow rate of the additional gas is increased (in this experimental example, 0.3 mm), and D2 is the additional gas. The case where the diameter of the small tube portion is made large so that the flow velocity of the tube is relatively slow is shown (2 millimeters in this experimental example). The graph shows various changes in the ratio between the gas G1 (first gas) and the additional gas G2 (second gas) introduced into the spray chamber 20 with a total flow rate of 1.05 liters / minute. The result of measuring the sensitivity under the conditions is shown.

  By the way, prior to the present application, the applicant of the present application, regardless of the flow rate of the additional gas, the gas introduced into the spray chamber (corresponding to G1 in the present application) and the additional gas introduced into the rear stage of the spray chamber (the present application). It is found that the decrease in sensitivity can be controlled with good reproducibility by controlling the proportion of additional gas in the total flow rate while keeping the total gas flow rate at a constant value by using a device that can control G2). ing. The sensitivity is reduced because the sample delivered from the spray chamber is reduced by reducing the flow rate of the gas introduced into the spray chamber. Such a technique is extremely effective for dilution when the above-described high matrix sample is used as the sample to be analyzed. That is, when analyzing a high matrix sample, the amount of gas reaching the plasma torch per unit time remains unchanged by reducing the flow rate of the gas introduced into the spray chamber and increasing the flow rate of the additional gas. This can reduce only the amount of the liquid, which makes it possible to dilute the high matrix sample and prevent the above-mentioned adverse effects. The applicant of the present application has filed a patent application as Japanese Patent Application No. 2006-219520 on August 11, 2006 for the invention.

  The present invention can be applied as a further improvement technique of the invention. That is, according to the present invention, the sample can be diluted more effectively by introducing the additional gas introduced in the invention according to the above-described application at a higher flow rate. In the present invention, by using the improved gas introduction method as described above, a part of the sample is changed to a droplet to become a part of the drainage, and the amount of the sample reaching the plasma torch is more effectively increased. It is decreasing.

  As can be seen from the graph of FIG. 7, in both D1 and D2, increasing the flow rate of the additional gas decreases the sensitivity. As a result of this experiment, a relatively large amount of droplets were formed in the case of D1, and a relatively small amount of droplets were formed in the case of D2. That is, in both cases of D1 and D2, a diluting action is caused by the formation of droplets.

  However, there is a difference between the two effects. In the case of D1, the sensitivity can be sufficiently lowered even when the flow rate of the additional gas is small compared to the case of D2. In other words, by adopting the method of making the gas flow of the present invention sufficiently faster, the flow rate of the additional gas required for reducing the sensitivity can be reduced. This is a practical advantage in that the degree of freedom in selecting the type of nebulizer used when spraying the analysis sample is increased, and the stable operation of the nebulizer can be ensured.

  Regarding the former, for example, a Babington-type nebulizer is used in a relatively narrow gas flow rate range and cannot be used at a low flow rate as compared to a concentric nebulizer. Therefore, if the flow rate of the additional gas G2 for reducing the sensitivity can be reduced as in the case of D1, the flow rate of the gas G1 introduced into the spray chamber can be maintained relatively high. The stable operation of the Babington nebulizer can be guaranteed.

  In addition, in the graph of FIG. 7, in the case of D2, there is a drop in sensitivity when the flow rate of the additional gas is 0.1 to 0.2 liter / min. It is understood that this is caused by the fact that the flow rate of the additional gas is not sufficiently high in the flow rate range. That is, in order to obtain the effect of the present invention, the condition of D1 is more suitable than D2. More specifically, when the additional gas has a predetermined flow rate, the flow rate when introduced into the transport pipe is at least 10 times the flow speed at which the first gas of the predetermined flow rate passes through the transport pipe, preferably Preferably, the cross-sectional area of the small pipe portion and the transport pipe and other dimensions and shapes are selected so as to exceed 50 times to 100 times. If a sufficient flow rate is obtained over the full flow range, the sensitivity may tend to monotonically decrease with increasing flow of additional gas, as shown by D1.

  As described above, the apparatus and method according to the preferred embodiment of the present invention have been described in detail. However, this is merely an example, and does not limit the present invention. Can be modified and changed.

It is a schematic block diagram which mainly represents the plasma production | generation means provided in the front | former stage in order to produce | generate plasma among the structures of the inductively coupled plasma mass spectrometer which becomes embodiment of this invention. It is the schematic which shows the effect | action of the gas introduce | transduced from a small pipe part. It is a schematic sectional drawing which shows the structural example of a small pipe part. It is a figure which shows the modification of a transport pipe. It is a figure which shows the further modification of a rising part. It is a figure explaining the modification which provided the washing | cleaning means. It is a graph showing the effect by the apparatus or method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Inductively coupled plasma mass spectrometer 20 Spray chamber 30 Plasma torch 40 Sample container 50 Interface 60 Nebulizer 70 Transport pipe 80 Small pipe part 90 Control apparatus G1 1st gas G2 2nd gas (additional gas)

Claims (20)

A spray chamber for atomizing a solution, which is an analysis sample, by spraying using at least a part of the introduced first gas; a transport pipe for transporting the atomized analysis sample together with the first gas; In a plasma analysis apparatus comprising a plasma generating means comprising a plasma torch connected to a transport pipe and introducing the analysis sample transported through the transport pipe into the plasma,
Introducing a second gas that does not react with the first gas at an intermediate position in the length direction of the transport pipe so as to generate an air flow from one side surface of the transport pipe toward the opposite surface; A part of the analysis sample atomized by the presence of an air flow is changed to a droplet at an intermediate position to adhere to the inner surface of the transport tube, and the total amount of the analysis sample reaching the plasma torch is reduced. A characteristic plasma analyzer.   The plasma analysis apparatus according to claim 1, wherein the second gas is introduced so as to form a jet into the transport pipe.   The flow rate when the second gas is introduced into the transport pipe is set to exceed at least 50 times the flow speed at which the first gas passes through the transport pipe. 2. The plasma analysis apparatus according to 2.   The plasma analysis apparatus according to claim 1, wherein the first gas and the second gas are the same component gas.   The transport pipe includes a rising portion extending upward from the spray chamber, the second gas is introduced from a small pipe portion connected to the rising portion, and the droplets are formed in the rising portion. The plasma analyzer according to claim 1, wherein the plasma analyzer is configured to adhere to an inner surface and move in a direction returning to the spray chamber along the inner surface by gravity.   6. The surface portion having high hydrophilicity or water repellency is provided on at least a part of the inner surface of the transport pipe from the introduction position of the second gas to the spray chamber. Plasma analyzer.   The plasma analysis apparatus according to claim 6, wherein the surface portion includes a portion processed into a frosted glass shape so as to enhance hydrophilicity.   The plasma analysis apparatus according to claim 6, wherein the surface portion includes a coating film provided on the inner surface so as to increase hydrophilicity or hydrophobicity.   7. The surface portion is provided by a part that constitutes at least a part of the length of the transport pipe and whose inner side surface is made of a material having hydrophilicity or water repellency. Plasma analyzer.   6. The plasma analysis apparatus according to claim 5, wherein the rising portion includes a cleaning unit that operates in a timely manner to assist the movement of the droplet in a direction returning to the spray chamber.   The plasma analysis apparatus according to claim 10, wherein the cleaning unit provides a liquid flow or a gas flow that flows toward the spray chamber from an intermediate position of the rising portion.   The plasma analysis apparatus according to claim 5, wherein the rising portion forms an angle of 45 degrees or more from a horizontal plane.   The transport of the small tube portion is such that the direction in which the second gas is introduced is at a right angle or an obtuse angle with respect to the direction in which the analysis sample atomized in the transport tube is transported. The plasma analysis apparatus according to claim 5, wherein the plasma analysis apparatus is connected to a tube.   The plasma analysis apparatus according to claim 5, wherein the small pipe portion is formed of a tubular member separate from the transport pipe.   The plasma analysis apparatus according to claim 1, further comprising a control device that controls a flow rate of the second gas.   The plasma analysis apparatus according to claim 15, wherein the control device controls a total flow rate of the first gas and the second gas and a ratio thereof. A step of sucking up the analysis sample which is a liquid from the sample container, and spraying the sucked analysis sample using at least a part of the first gas introduced into the spray chamber, and atomizing the analysis sample into the spray chamber. A step of generating, a step of transporting the atomized analysis sample together with the first gas to lead to a plasma torch, a step of bringing the atomized analysis sample into a plasma state by the plasma torch, and plasma In a plasma analysis method comprising the step of detecting an ion extracted from plasma or detecting ions extracted from plasma and identifying an element,
The step of introducing the atomized analysis sample to the plasma torch includes a second gas that does not react with the first gas at a position halfway along the length of the transport pipe. Introducing the air flow from the side surface to the opposite surface, introducing a part of the analysis sample atomized by the presence of the air flow into a droplet at an intermediate position to adhere to the inner surface of the transport tube, the plasma A plasma analysis method comprising a step of reducing the total amount of the analysis sample reaching the torch.   The plasma analysis method according to claim 17, wherein the first gas and the second gas are the same component gas.   18. The plasma of claim 17, wherein the step of directing the atomized analytical sample to a plasma torch further comprises moving the generated droplets to the spray chamber by gravity. Analysis method.   The plasma analysis according to claim 19, wherein the step of introducing the atomized analysis sample to the plasma torch includes a step of cleaning at least a part of the transport pipe using an air flow or a water flow in a timely manner. Method.

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