JP2016008918A - Inductively coupled plasma mass spectrometry method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inductively coupled plasma mass spectrometry method whose degradation in detection sensitivity and analysis accuracy can be suppressed even if analysis is continuously performed without diluting sample solution.SOLUTION: The inductively coupled plasma mass spectrometry method is provided which uses an inductively coupled plasma mass spectrometer that comprises: a sample introduction part which sprays sample solution to carrier gas to form sample mist; an ICP (Inductively Coupled Plasma) generation part which has a plasma torch generating inductively coupled plasma of the sample; a mass separation part which separates ions of the sample according to a mass-to-charge ratio; and a conical sampler which is arranged between the ICP generation part and the mass separation part, and induces inductively coupled plasma of the sample to the mass separation part. The method includes: an analysis step of supplying the sample introduction part with the sample solution as raw solution unchanged without diluting and analyzing the sample solution; and a cleaning step of removing deposit from the sampler by using plasma generated by the plasma torch.

Description

  The present invention relates to an inductively coupled plasma mass spectrometry method capable of continuously analyzing a sample with high accuracy using an inductively coupled plasma mass spectrometer.

  A mass spectrometry method using inductively coupled plasma (hereinafter sometimes referred to as ICP-MS) uses inductively coupled plasma as an ionization source to be introduced into a mass spectrometer, and is currently known for analyzing elements. Among the methods, it is one of the analytical methods capable of quantitative and qualitative analysis with the highest sensitivity.

  In ICP-MS, a sample liquid is sprayed into a carrier gas such as argon to generate a mist containing a sample, and components are ionized by thermal excitation by a plasma apparatus. Then, the constituent component including the ionized component to be analyzed is introduced into the vacuum mass analyzer by a sampler having pores at the conical metal tip. The mass analysis unit includes a focusing lens, a mass separation device such as a double focusing type mass separation unit or a quadrupole filter, and a detector, and measures ions according to the mass number as an electric quantity. The target component in the sample is quantified based on the relationship between the amount of electricity and the concentration of the sample (see, for example, Patent Document 1).

  In ICP-MS, ions generated under atmospheric pressure need to be reduced in pressure to a vacuum state through a sampler having pores. For this reason, when a sample solution having a high salt concentration is used for analysis, a solidified sample may be deposited on the surface of the sampler. For this reason, if a sample solution with a high concentration is used for continuous analysis by ICP-MS, the solidified sample is deposited on the surface of the sampler, and the amount of ion introduction and the efficiency of ion introduction into the mass analyzer are reduced. As a result, there is a problem that the analysis sensitivity is lowered.

  For this reason, when performing analysis by ICP-MS continuously using a sample solution having a high salt concentration, a method of diluting the concentration of the sample solution to, for example, about 1 mg / L so that the sample does not precipitate on the surface of the sampler. It has been known. There is also known a method of diluting a sample solution with a gas such as argon gas without diluting with a liquid such as water.

Japanese Patent No. 4903515

  However, in the analysis by ICP-MS, in order to reduce the adhesion of the sample to the surface of the sampler, if the sample solution with a high salt concentration is diluted with a liquid or gas before use, the detection sensitivity of the elements constituting the sample In addition, there is a problem that the analysis accuracy is lowered. There is also a concern that the sample may be contaminated by impurities contained in a dilution medium such as liquid or gas.

  The present invention has been made in view of the above-described situation. Inductive coupling capable of suppressing a decrease in detection sensitivity and analysis accuracy even when analysis is continuously performed without diluting a sample solution. An object of the present invention is to provide a plasma mass spectrometry method.

  In order to solve the above problems, the inductively coupled plasma mass spectrometry method of the present invention includes a sample introduction part that forms a sample mist by spraying a sample liquid with a carrier gas, and a plasma torch that generates inductively coupled plasma, An ICP generator that ionizes elements constituting the sample by introducing a sample mist, a mass separator that separates ions of the sample according to a mass-to-charge ratio, and an ICP generator and the mass separator. And an inductively coupled plasma mass spectrometry method using an inductively coupled plasma mass spectrometer equipped with a conical sampler for guiding the inductively coupled plasma of the sample to the mass separation unit, wherein the sample liquid is diluted The sample solution is supplied as it is to the sample introduction part and analyzed, and the sampler is attached using the plasma generated by the plasma torch. Characterized by comprising a cleaning step of removing.

  According to the inductively coupled plasma mass spectrometry method of the present invention, even if the sample liquid is used for analysis without being diluted and the components of the sample liquid are deposited on the sampler, the deposit can be removed by the cleaning process. Therefore, even if it analyzes continuously, it becomes possible to prevent the fall of the detection sensitivity and analysis accuracy by a deposit. Further, even when the sample solution is used without being diluted, the opening of the sampler is prevented from being clogged with precipitates, and continuous analysis can be performed.

The cleaning step is characterized in that the supply of the carrier gas is stopped and the interval between the plasma torch and the sampler is narrower than that in the analysis step.
As a result, the sampler is exposed to high temperature due to plasma, and the deposits deposited on the sampler can be reliably decomposed and removed.

The cleaning step further includes a step of flowing a cleaning liquid to the sample introduction portion to wash the sample introduction portion.
As a result, the sample liquid remaining in the sample introduction part is completely removed, and at the next analysis, impurity contamination by the sample liquid used in the previous analysis can be prevented and high-precision analysis can be performed continuously. To.

The sampler includes a sampling cone and a skimmer cone disposed on the rear side of the sampling cone.
In the present invention, the deposits deposited on both the sampling cone and the skimmer cone can be decomposed and removed by exposing the sampling cone and the downstream-side skimmer cone to high-temperature plasma in the cleaning process.

  According to the inductively coupled plasma mass spectrometry method of the present invention, it is possible to suppress a decrease in detection accuracy even if the analysis is continuously performed without diluting the sample solution.

It is a block diagram which shows an example of the inductively coupled plasma mass spectrometer used for the inductively coupled plasma mass spectrometry method of this invention. It is sectional drawing which shows the plasma torch and sampler of an inductively coupled plasma mass spectrometer. It is the flowchart which showed the inductively coupled plasma mass spectrometry method of this invention in steps. It is a graph which shows the verification result of the example of the present invention. It is a graph which shows the verification result of the example of the present invention. It is a graph which shows the verification result of the example of the present invention. It is a graph which shows the verification result of the example of the present invention. It is a graph which shows the verification result of the example of the present invention. It is a graph which shows the verification result of the example of the present invention. It is a graph which shows the verification result of the example of the present invention. It is a graph which shows the verification result of a comparative example.

(Inductively coupled plasma mass spectrometer)
First, an inductively coupled plasma mass spectrometer used in the inductively coupled plasma mass spectrometry method of the present invention will be described.
Note that the term “dilution” in the present invention is to reduce the amount of sample ions passing through the ICP generation unit 12 described later, and dilution using a liquid or so-called “dry” method without using a liquid is also possible. That means.
FIG. 1 is a configuration diagram illustrating an example of an inductively coupled plasma mass spectrometer.
The inductively coupled plasma mass spectrometer 10 includes a sample introduction unit 11, an ICP generation unit 12, a mass separation unit 13, and a sampler 14 disposed between the ICP generation unit 12 and the mass separation unit 13. .

  The sample liquid introduction unit 11 includes a sample liquid table 21, a liquid supply pump 22, a sprayer 23, a spray chamber 24, a carrier gas supply unit 25, an additive gas supply unit 26, and a plurality of pipes 27 connecting them. .

The sample liquid table 21 holds a plurality of sample liquids R stored in a container, and introduces a suction tube 28 to any sample liquid R. The sample liquid table 21 can also hold a container containing the cleaning liquid C.
As the sample liquid R, in the present embodiment, a liquid having a high salt concentration such as seawater is used as it is without being diluted. The cleaning liquid C uses, for example, pure water, dilute nitric acid, dilute hydrochloric acid, or the like.

  The liquid supply pump 22 sucks the sample liquid R and the cleaning liquid C through the suction pipe 28 inserted into the sample liquid R and the cleaning liquid C, and supplies it to the sprayer 23. As the liquid supply pump 22, a peristaltic pump, a syringe pump, or the like can be used.

  The sprayer 23 is supplied with the sample liquid R and a carrier gas for generating an aerosol of the sample liquid R from the carrier gas supply unit 25. As the carrier gas, an inert gas or air is preferably used, and in this embodiment, argon gas is used. The nebulizer 23 aerosolizes the sample liquid R. This aerosolized sample liquid R (hereinafter sometimes referred to as sample mist) is carried by the carrier gas flow and introduced into the ICP generator 12.

  The sprayer 23 is arranged such that a tip portion thereof is exposed in the spray chamber 24. The spray chamber 24 includes a cylindrical wall through which a droplet of sample mist can circulate. The sample mist is supplied to the ICP generator 12 by the carrier gas flow. On the other hand, droplets having a relatively large diameter are discharged from a drainage drain 29 connected to the bottom of the spray chamber 24.

  Connected between the spray chamber 24 and the ICP generator 12 is an additive gas supply unit 26 that introduces additive gas into the sample mist. For example, argon gas is used as the additive gas supplied from the additive gas supply unit 26.

The ICP generation unit 12 includes a plasma torch 31 and a plasma gas supply unit 32.
FIG. 2 is a cross-sectional view showing an outline of a plasma torch and a sampler. The plasma torch 31 includes a plasma generating cylinder 32 having an open surface 32a at one end, a sample mist introducing section 33 connected to the plasma generating cylinder 32, a plasma gas introducing section 34, and a load coil 35. In addition, it is preferable that a cooling gas flow path (not shown) for flowing a cooling gas for cooling the plasma generating cylinder 32 is further formed on the outer periphery of the plasma generating cylinder 32.

The plasma generating cylinder 32 is a cylindrical member, and the inside of the plasma generating cylinder 32 is a plasma generating chamber 36 that generates plasma of elements constituting argon and the sample liquid.
The sample mist introduction unit 33 introduces the sample mist supplied from the spray chamber 24 into the plasma generation chamber 36.

  One end of the plasma gas introduction unit 34 is connected to the plasma gas supply unit 32, and the plasma gas is introduced from the plasma gas introduction unit 34 into the plasma generation chamber 36. As the plasma gas, for example, an inert gas such as argon gas or helium gas is used. In this embodiment, argon gas is used as the plasma gas.

  The load coil 35 is a conductor wound along the outer peripheral surface of the plasma generating cylinder 32, and a high frequency current that is energy for generating the plasma Z is applied to the plasma generating chamber 36. By applying a high frequency current to the load coil 35 with the plasma gas introduced into the plasma generation chamber 36, the plasma Z can be brought into an ignition state. Thereafter, for the analysis of the sample liquid R, the sample mist is introduced from the sample mist introduction unit 33. Thereby, each element constituting the sample liquid is ionized in the plasma Z. The plasma Z is emitted from the open surface 32a of the plasma generating cylinder 32 toward the sampler 14. These are supported by the plasma torch moving device 43. The plasma torch moving device 43 moves the unitized load coil 35 and the plasma generating cylinder 32 in the horizontal direction. As a result, the distance between the open surface 32a of the plasma generating cylinder 32 and the sampling cone 41 constituting the sampler 14 can be made closer or separated.

  The sampler 14 includes a sampling cone 41 and a skimmer cone 42. The sampling cone 41 is a conical member, and an opening 41a is formed at the position of the tip of the cone. The skimmer cone 42 is a conical member having a smaller diameter than the sampling cone 41, and a part thereof is arranged to overlap the sampling cone 41. The clearance cone 42 is formed with an opening 42a at the tip of the cone so as to overlap the opening 41a of the sampling cone 41 on the same axis.

  The plasma torch 31 including the load coil 35 is supported by the plasma torch moving device 43. The plasma torch moving device 43 moves the unitized load coil 35 and plasma torch 31 in the horizontal direction. As a result, the distance between the open surface 32a of the plasma generating cylinder 32 and the sampling cone 41 constituting the sampler 14 can be made closer or separated.

  The interval between the plasma torch 31 and the opening 41a of the sampling cone 41 is generally called the sampling depth (D). Such a sampling depth D is precisely the distance between the position of the opening 41a of the sampling cone 41 and the position of the outermost end of the load coil 35 on the sampler 14 side.

  In general, if the sampling depth D is small, the amount of ions passing through the opening 41a of the sampling cone 41 and the opening 42a of the skimmer cone 42 increases, and conversely if the sampling depth D is large, the ions passing therethrough. The amount tends to decrease. Therefore, the number of ions passing through the sampler 14 can be changed by adjusting the sampling depth D indicating the distance between the plasma torch 31 and the sampling cone 41. Further, the plasma has a temperature distribution, and when the sampling depth D is changed, the temperature region of the plasma that is in close contact with the opening 41a of the sampling cone 41 can be controlled. That is, by setting the sampling depth D that matches the ionization potential of the element to be measured, it is possible to select and analyze the temperature region that provides the optimum ionization efficiency.

Referring again to FIG. 1, the mass separation unit 13 includes a focusing lens 51, a mass separation device 52, and a detection device 53.
The focusing lens 51 focuses ions transmitted through the sampler 14 toward the mass separation device 52. An ion lens is used as the focusing lens 51.

  The mass separation device 52 separates ions introduced through the focusing lens 51 according to the mass-to-charge ratio. As the mass separation device 52, a quadrupole separation device, a magnetic field deflection separation device, an ion trap separation device, or the like can be used. Of these, the quadrupole separation device passes ions through four electrodes, applies a high frequency voltage to each electrode, perturbs the ions, and transmits only specific ions. When ions pass through the four electrodes, the voltage value of each electrode is changed to change the mass-to-charge ratio of ions that can pass through, thereby obtaining a mass spectrum. In the present embodiment, a quadrupole separator is used as the mass separator 52.

  The detection device 53 detects ions separated for each mass-to-charge ratio in the mass separation device 52. As the detection device 53, for example, an electron multiplier, a microchannel plate, or the like can be used. Such a detection device sensitizes and detects ions that have passed through the mass separation device 52.

In addition, from the sampler 14 to the mass separation part 13, it is made into the pressure reduction environment with a vacuum pump (not shown). For example, the pressure is gradually reduced from the ICP generation unit 12 in the atmospheric pressure environment toward the detection device 53 having a degree of vacuum of about 1 × 10 ⁻⁶ torr.

(Inductively coupled plasma mass spectrometry method)
The inductively coupled plasma mass spectrometry method of the present invention using the inductively coupled plasma mass spectrometer having the above configuration will be described with reference to FIGS.
FIG. 3 is a flowchart showing steps of the inductively coupled plasma mass spectrometry method of the present invention step by step.
When performing qualitative and quantitative analysis of a specific element contained in a sample liquid using the inductively coupled plasma mass spectrometer 10 shown in FIG. 1, first, a container containing the sample liquid R to be analyzed is placed in a sample liquid table. 21 (sample preparation step S1). In the present embodiment, seawater is used as the sample solution R. In order to improve the analysis accuracy, seawater is used for analysis without being diluted. The salt concentration of such seawater is generally about 3.5%. In addition, a container in which the cleaning liquid C is previously placed is also placed on the sample liquid table 21. As the cleaning liquid C, for example, pure water, dilute nitric acid, dilute hydrochloric acid, a surfactant, or the like can be used.

  Next, the liquid supply pump 22 is operated to suck up the sample liquid R placed on the sample liquid table 21 from the suction pipe 28 and replace the inside of the pipe 27 of the sample liquid introduction part 11 with the sample liquid R (preliminary). Suction step S2). The rotation speed of the liquid supply pump 22 is set at a higher speed than that in the stabilization process and the analysis process described later, and a large amount of the sample liquid R is filled in the pipe 27 in a short time.

  In the preliminary suction step S 2, the sample liquid R is sprayed from the nebulizer 22 to form a sample mist in the spray chamber 24, and a carrier gas, for example, an argon gas starts to flow from the carrier gas supply unit 25. Then, a plasma gas is supplied from the plasma gas introduction unit 34 to the plasma torch 31, and a high frequency current is applied to the load coil 35 of the plasma torch 31. As a result, plasma is generated in the plasma generation chamber 36 of the plasma torch 31.

  In the preliminary suction step S2, the flow rate of the additive gas and the rotation speed of the liquid supply pump 22 can be arbitrarily set. On the other hand, the flow rate of the carrier gas and the sampling depth are preferably matched with the settings in the analysis process described later. The time for performing the stabilization step S3 varies depending on the path length of the pipe 27, the flow rate of the carrier gas, the rotation speed of the liquid supply pump 22, and the like, so that the inside of the pipe 27 is sufficiently replaced with the sample liquid R, In addition, it is desirable to set a sufficient time for the plasma of the plasma torch 31 to stabilize.

  As an example of setting values of each part in the preliminary suction step S2, the flow rate of the carrier gas: 1.15 L / min, the sampling depth D (see FIG. 2): 14.5 mm, the rotation speed of the liquid feed pump: 100 rpm, the holding time (Execution time): 20 sec.

  When the inside of the pipe 27 is sufficiently replaced with the sample liquid R, the number of revolutions of the liquid supply pump 22 is then decreased as compared with the preliminary suction process S2, and the apparatus is stabilized (stabilization process S3). In the stabilization step S3, after the preliminary suction step S2, the number of rotations of the liquid supply pump 22 is set to the number of rotations in the analysis step to define the sample liquid introduction amount. Since a large amount of sample liquid is introduced into the pipe 27 by increasing the pump rotation speed in the preliminary suction step S2, the plasma temperature of the plasma torch 31 is lowered. Therefore, the ionization efficiency has changed, so the process necessary to stabilize the plasma temperature, ionization efficiency, etc. during the analysis process by holding for a certain time according to the amount of sample introduced in the analysis process It is.

  In the stabilization step S3, it is preferable that the number of revolutions of the feed pump 22, the flow rate of the carrier gas, and the sampling depth are set in accordance with the settings in the analysis step which is a subsequent step. The time for performing the stabilization step S3 is desirably set to a time sufficient for the entire inductively coupled plasma mass spectrometer 10 to be stabilized under the set conditions in the analysis step.

  As an example of the set values of each part in the stabilization step S3, the flow rate of the carrier gas: 1.15 L / min, the sampling depth D: 14.5 mm, the number of revolutions of the feed pump: 10 rpm, the holding time (execution time): It can be 15 sec.

  The sample liquid R is actually analyzed (measured) using the inductively coupled plasma mass spectrometer 10 thus prepared for analysis (analysis step S4). In the analysis step S4, the sample mist carried by the carrier gas is exposed to the plasma formed by the plasma torch 31, and the components of the sample liquid R, that is, the constituent components of seawater are ionized for each element. In the analysis step S4, the set values of the respective parts are the same as those in the stabilization step S3.

  As an example of setting values of each part in the analysis step S4, the flow rate of the carrier gas: 1.15 L / min, the sampling depth D: 14.5 mm, the rotation speed of the liquid supply pump: 10 rpm, the holding time (execution time): 15 sec can do. Further, it is preferable not to flow the additive gas in order to ionize the sample mist without diluting and improve the analysis accuracy. However, an additive gas may be flowed in optimizing the analysis conditions.

  The element ionized by the plasma torch 31 is focused by the focusing lens 51 and then introduced into the mass separator 52. In the mass separator 52, ions are separated according to the mass-to-charge ratio. For example, in a quadrupole separator, a high frequency voltage is applied to each electrode to perturb ions and transmit only specific ions. At this time, by changing the voltage value of each electrode, the mass-to-charge ratio of ions that can pass through changes.

  The ions separated for each mass to charge ratio by the mass separator 52 are introduced into the detector 53. The detection device 53 sensitizes and detects ions. Thereby, a mass spectrum for each ion is obtained.

  By the above analysis step S4, qualitative analysis and quantitative analysis of the components constituting the sample liquid R can be performed. In the analysis step S4, depending on the element to be measured, in order to improve the sensitivity, reduce the background, or remove the interference of coexisting components, the carrier gas flow rate is changed, and the sampling depth D is changed during the analysis. Alternatively, the additive gas may be introduced or stopped. Depending on the device configuration of the inductively coupled plasma mass spectrometer 10, the type of additive gas may be changed for analysis, and various combinations of conditions can be combined depending on the inductively coupled plasma mass spectrometer to be used and the components to be analyzed. is there.

When the analysis process S4 of one time (one turn) is completed, the cleaning process S5 is performed next.
The cleaning step S5 includes a cone cleaning step S5a and a tube / chamber cleaning step S5b.

  When analysis is performed without diluting the sample liquid R in order to ensure detection sensitivity and / or to improve analysis accuracy, the components of the sample liquid R ionized by the plasma torch 31 are converted into the sampling cone 41 and It becomes easy to deposit on the surface of the skimmer cone 42. When such deposits increase, the opening 41a of the sampling cone 41 and the opening 42a of the skimmer cone 42 may be blocked by the deposit. Such precipitates also reduce detection sensitivity and analysis accuracy. For this reason, in the cone cleaning step S5a, precipitates generated on the sampling cone 41 and the skimmer cone 42 constituting the sampler 14 are removed.

  In the cone cleaning step S5a, first, the supply of the carrier gas is stopped. Further, the liquid supply pump 22 is stopped, and the spraying of the sample liquid R is stopped. As a result, the sample mist basically does not reach the plasma torch 31.

  Further, the plasma torch moving device 43 is driven to move the plasma torch 31 so as to approach the sampling cone 41 and the skimmer cone 42 side. As a result, the distance between the plasma torch 31 and the sampler 14, that is, the sampling depth D, is narrower than in the analysis step S4.

In such a state, the plasma gas is continuously supplied to the plasma torch 31 to maintain the plasma generation state.
As an example of setting values of each part in the cone cleaning step S5a, carrier gas: stop, sampling depth D: 5.0 mm, feed pump: stop, holding time (execution time): 20 sec. It is also preferable to flow an additive gas, for example, argon gas, from the additive gas supply unit 26 at about 1.15 L / min.

  By such a cone cleaning step S5a, the plasma torch 31 and the sampler 14 come closer to each other than the analysis step S4, and the sampling cone 41 and the skimmer cone 42 are exposed to a high temperature due to plasma. As a result, the deposits attached to the sampling cone 41 and the skimmer cone 42, for example, the salinity constituting the seawater, are decomposed, evaporated and removed, and the surfaces of the sampling cone 41 and the skimmer cone 42 are cleaned.

  There is a correlation between the sampling depth D of the plasma in the cone cleaning step S5a and the execution time of the cone cleaning step S5a and the deposit removal effect of the sampler 14, and the longer the sampling time, the longer the execution time. In this case, since the time of one cycle from the entire analysis to the cleaning becomes long, it is desirable to set so that the operation rate does not extremely decrease. Further, if the sampling depth is reduced, the execution time of the cone cleaning step S5a can be shortened. In this case, it is desirable to set so that the sampler 14 does not undergo thermal alteration due to high temperature.

  S5b is performed as a subsequent process of the cone cleaning process S5a. In the tube chamber cleaning step S5b, the liquid supply pump 22 is operated while the supply of the carrier gas is stopped. Further, the suction tube 28 is introduced into the cleaning liquid C of the sample liquid table 21, for example, pure water, diluted nitric acid, and diluted hydrochloric acid. As a result, the pipe 27 of the sample liquid introduction unit 11 is replaced with the cleaning liquid C. Further, since the carrier gas is not introduced into the sprayer 23, the cleaning liquid C that has flowed into the sprayer 23 flows down from the spray chamber 24 toward the drainage drain 29 as droplets.

  As an example of setting values of each part in the tube / chamber cleaning step S5b, carrier gas: stop, sampling depth D: 5.0 mm, rotation speed of liquid feed pump: 100 rpm, holding time (execution time): 30 sec. it can. It is also preferable to flow an additive gas, for example, argon gas, from the additive gas supply unit 26 at about 1.15 L / min.

  The cleaning step S5 as described above removes precipitates from the surfaces of the sampling cone 41 and the skimmer cone 42 constituting the sampler 14 even when seawater containing high-concentration salinity is used as the sample solution R without being diluted. Therefore, in the next analysis step, a decrease in detection sensitivity and analysis accuracy due to precipitates generated by the previous analysis is prevented. Even if seawater containing high-concentration salinity is used as the sample liquid R without diluting it, it is possible to perform continuous analysis by preventing the opening of the sampling cone 41 and the skimmer cone 42 from being blocked by deposits. To.

  When there is another sample liquid R after the completion of the cleaning step S5 (S6), the analysis step S4 can be performed continuously through the preliminary suction step S2 and the stabilization step S3. Even if the analysis step S4 is continuously performed, by performing the cleaning step S5 each time, even if seawater containing high-concentration salinity is used as the sample solution R without being diluted, a constant detection sensitivity and high It becomes possible to perform qualitative analysis and quantitative analysis of the sample liquid R while maintaining analysis accuracy.

The inductively coupled plasma mass spectrometry method of the present invention has been described above, but the present invention is not limited to this, and can be appropriately changed without departing from the technical idea of the present invention.
For example, in the above-described embodiment, argon gas is used as the carrier gas, the additive gas, and the plasma gas. However, the present invention is not limited to this, and various inert gases can be used. Further, the flow rate of the carrier gas, the sampling depth, the number of rotations of the liquid supply pump, and the like are examples of settings and are not limited thereto. Although the sampler 14 has shown the example comprised from the sampling cone 41 and the skimmer cone 42, it is not restricted to this, The sampler may be comprised only by the sampling cone.

Hereinafter, verification results verifying the effects of the present invention will be described.
(Example of the present invention)
The inductively coupled plasma mass spectrometry method of the present invention described above was performed using the inductively coupled plasma mass spectrometer having the configuration shown in FIG. As the sample liquid, seawater was used without being diluted, and quantitative analysis of yttrium (Y), indium (In), tellurium (Te), and cesium (Cs) in the seawater was performed.
Tables 1 to 7 show the carrier gas flow rate setting, additive gas flow rate setting, plasma sampling depth, number of revolutions of the liquid supply pump, and the implementation time (holding time) of each step in each of the inventive examples 1-7. 7 respectively.

(Comparative example)
Using the inductively coupled plasma mass spectrometer having the configuration shown in FIG. 1, each step of the inductively coupled plasma mass spectrometry method of the present invention except for the cone cleaning step S5a was performed. As the sample liquid, seawater was used without being diluted, and quantitative analysis of yttrium (Y), indium (In), tellurium (Te), and cesium (Cs) in the seawater was performed.
Table 8 summarizes the carrier gas flow rate setting, the additive gas flow rate setting, the plasma sampling depth, the number of revolutions of the feed pump, and the holding time (implementation time) of each step in each process in the comparative example. .

In each of the inventive examples 1 to 7 and the comparative example, each cycle was set as one cycle, and 60 cycles of analysis were continuously performed. Then, the change (relative value) in the detected amount up to the 60th cycle was examined with the detected amount in the first cycle of each element (Y, In, Te, Cs) as 100. In the example of the present invention, seven patterns in which the flow rate of the additive gas was set and the sampling depth of the plasma were changed were implemented.
The results of Invention Examples 1 to 7 are shown in FIGS. 4 to 10, and the results of Comparative Examples are shown in FIG.
(Invention Example 1: FIG. 4, Invention Example 2: FIG. 5, Invention Example 3: FIG. 6, Invention Example 4: FIG. 7, Invention Example 5: FIG. 8, Invention Example 6: FIG. (Invention Example 7: FIG. 10, Comparative Example: FIG. 11)

  According to the verification results of the examples of the present invention shown in FIGS. 4 to 11, when the analysis is continuously performed according to the present invention, detection of 90% or more is detected with respect to the analysis result of the first turn in all the elements quantified. It was confirmed that the analysis can be performed continuously with low sensitivity and coefficient of variation and with stable analysis accuracy. Further, from the results of the present invention example, it was found that when the sampling depth is increased, the cleaning effect of the sampler is lowered, and the detection sensitivity and measurement accuracy tend to gradually decrease toward the time of 60 turns measurement. Further, it was found that when the additive gas is flowed, the cleaning effect of the sampler is lowered because the plasma temperature is lowered, and fluctuations in detection sensitivity and analysis accuracy tend to increase. It should be noted that if excessively high temperature plasma is applied to the sampler, the sampler may be damaged by heat. Therefore, it is preferable to suppress the plasma temperature within a certain range.

  On the other hand, in the conventional example in which the cone cleaning step S5a is not performed, the detection sensitivity and the analysis accuracy are reduced as the analysis is continuously performed for the analysis result of the first turn. %. Moreover, the fluctuation range of the detection sensitivity and analysis accuracy for each analysis turn of each element is large. In such a conventional example, it was confirmed that it was difficult to continuously analyze the sample liquid with a stable and high detection sensitivity and analysis accuracy. Such a decrease in detection sensitivity and analysis accuracy is thought to be due to deposition of precipitates on the sampler.

DESCRIPTION OF SYMBOLS 10 Inductively coupled plasma mass spectrometer 11 Sample introduction part 12 ICP production | generation part 13 Mass separation part 14 Sampler 31 Plasma torch 41 Sampling cone 42 Skimmer cone R Sample liquid

Claims (4)

A sample introduction unit that forms a sample mist by spraying a sample liquid into a carrier gas, an ICP generation unit having a plasma torch that generates inductively coupled plasma of the sample, and ions of the sample are separated according to mass-to-charge ratio And a conical sampler disposed between the ICP generation unit and the mass separation unit for guiding the inductively coupled plasma of the sample to the mass separation unit. An inductively coupled plasma mass spectrometry method using
An analysis step of analyzing the sample liquid by supplying the sample liquid as it is without diluting the sample liquid to the sample introduction unit;
A cleaning step of removing deposits on the sampler using plasma generated by the plasma torch;
An inductively coupled plasma mass spectrometry method comprising:   2. The inductively coupled plasma mass spectrometry method according to claim 1, wherein in the cleaning step, the supply of the carrier gas is stopped, and an interval between the plasma torch and the sampler is narrower than that in the analysis step.   3. The inductively coupled plasma mass spectrometry method according to claim 1, further comprising a step of cleaning the sample introduction unit by flowing a cleaning liquid to the sample introduction unit in the cleaning step.   The inductively coupled plasma mass spectrometry method according to any one of claims 1 to 3, wherein the sampler includes a sampling cone and a skimmer cone disposed on a rear stage side of the sampling cone.

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