阅读说明：本技术 样品分析方法、样品导入装置 (Sample analysis method and sample introduction device ) 是由 荒木健司 于 2018-12-20 设计创作，主要内容包括：利用喷雾器(4)将样品溶液转换为样品雾气之后,在脱溶媒部(7)通过加热使之进行脱溶媒,将含有经脱溶媒后的样品雾气和载气的样品气体通过样品导入管(9)倒入到电浆炬30。在样品导入管(9)设置添加部(10),其添加含有水分的载气即含水气体。添加部(10)具备：容器(11),其装有超纯水；气体管(12),其向超纯水中导入载气并使其起泡；及气体管(14),其将由起泡产生的含水气体添加到样品导入管(9)。电浆炬(30),以将供给电力设为550 W~700 W的条件产生感应耦合电浆。由此,将含有通过加热而脱溶媒的样品雾气和搬送该样品雾气的载气的样品气体导入到电浆中,并对通过电浆而离子化的样品中的元素进行分析时,抑制因为离子化电位较高的元素所引起的干扰分子离子的产生。(After the sample solution is converted into a sample mist by a nebulizer (4), the sample solution is heated in a solvent removing part (7) to remove the solvent, and the sample gas containing the solvent-removed sample mist and a carrier gas is poured into a plasma torch (30) through a sample introduction tube (9). An addition part (10) is provided in the sample introduction tube (9) and adds a water-containing gas, which is a carrier gas containing water. The addition unit (10) is provided with: a container (11) containing ultrapure water; a gas pipe (12) for introducing a carrier gas into the ultrapure water and bubbling the ultrapure water; and a gas pipe (14) for adding the water-containing gas generated by the bubbling to the sample introduction pipe (9). The plasma torch (30) generates inductively coupled plasma under the condition that the supplied power is set to 550W-700W. Thus, when a sample gas containing a sample mist from which a solvent is removed by heating and a carrier gas for transporting the sample mist is introduced into plasma and an element in the sample ionized by the plasma is analyzed, generation of interfering molecular ions due to the element having a high ionization potential is suppressed.)

1. A sample analysis method for analyzing an element in a sample ionized by plasma by introducing into the plasma a sample gas containing a sample mist from which a solvent is removed by heating and a carrier gas for transporting the sample mist, characterized in that:

a carrier gas containing moisture, i.e., a moisture-containing gas, is added to a path for introducing the sample gas into the plasma.

2. The sample analysis method according to claim 1, characterized in that:

the aqueous gas is generated by bubbling a carrier gas in ultrapure water.

3. The sample analysis method according to claim 1, characterized in that:

the aqueous gas is generated by immersing a gas-carrying line composed of a hollow fiber filter in ultrapure water.

4. A sample analysis method as claimed in any one of claims 1 to 3, wherein:

the plasma is inductively coupled plasma generated by setting the supplied power to 550W-700W.

5. A sample introduction apparatus for introducing a sample gas into a plasma, the apparatus being applied to a method comprising: introducing a sample gas containing a sample mist from which a solvent is removed by heating and a carrier gas for transporting the sample mist into plasma, and analyzing elements in the sample ionized by the plasma; the sample introduction device is characterized by comprising:

a generation unit that generates a moisture-containing gas that is a carrier gas containing moisture; and

a path for adding the water-containing gas generated in the generating section to a path for introducing the sample into the plasma.

6. The sample introduction device according to claim 5, wherein:

the generating section generates the water-containing gas by bubbling a carrier gas in ultrapure water.

7. The sample introduction device according to claim 5, wherein:

the generating section generates the water-containing gas by immersing a carrier gas composed of a hollow fiber filter in ultrapure water.

8. The sample introduction device according to any one of claims 5 to 7, wherein:

the plasma is an inductively coupled plasma generated by setting the supply power to 550W-700W.

Technical Field

The present invention relates to a method for introducing a sample into plasma to ionize the sample and analyzing elements in the ionized sample and an apparatus for introducing the sample into the plasma.

Background

An Inductively Coupled Plasma mass spectrometer (ICP-MS) generates Inductively Coupled Plasma by supplying high frequency power to an induction coil disposed in a Plasma torch, and ionizes elements contained in a sample by spraying an aerosolized sample solution onto a center portion of the Plasma. The apparatus is an apparatus in which ions are introduced into a vacuum system through a plasma interface, separated into target masses by a mass analyzer, and then counted by a detector, thereby identifying or quantifying the ions (elements). ICP-MS is characterized by high sensitivity and wide linear range of calibration curve.

The ICP-MS is composed of the following parts: a sample introduction part for spraying and introducing a sample solution, a plasma torch part for ionizing elements contained in the sprayed sample, an interface part for capturing ions to a vacuum system of a mass analyzer, an ion lens part for efficiently guiding ions to the mass analyzer, a mass separation part for performing mass separation of ions, and an ion detection part for performing ion detection.

Wherein the sample introduction section sprays the sample solution through the sprayer, and the mist of the sample carried by the carrier gas is screened through the spray chamber. That is, the mist of the sample having a small particle size is carried to the plasma torch by the carrier gas. Generally, the particle size of the transported sample mist is screened by the spray chamber, but the spray chamber only contributes to transport of a small sample mist to the plasma torch, and therefore the sample introduction efficiency is low. Therefore, for the purpose of improving the efficiency of sample introduction into the plasma torch, ultrasonic atomizers, and desolventizing-medium sample introduction apparatuses such as APEX and DHS have been commercialized.

The ultrasonic nebulizer converts a sample into a fine mist by flowing a sample solution on the surface of the ultrasonic transducer, and can improve sample introduction efficiency as compared with a nebulizing chamber. However, many components of the ultrasonic nebulizer are glass products, and a sample containing hydrofluoric acid cannot be introduced. On the other hand, the desolvation sample introducing device includes APEX (ESI) and DHS (IAS), and a hydrofluoric acid-resistant chamber is provided, and a sample containing hydrofluoric acid can be introduced. In the desolvation sample introducing device, the sample mist generated by the sprayer is heated in the heating chamber, the solvent in the sample mist is gasified, the particle size of the sample mist is reduced, and the sample mist is overlapped with the carrier gas, so that the sample mist is easy to transport. The solvent vapor vaporized in the heating chamber is cooled to coagulate the solvent, and the solvent can be discharged as drain water. The configuration and operation of the desolvation sample introducing device are also described in patent document 1.

The particle size of the sample mist is reduced by the solvent removal sample introduction device, thereby improving the sample introduction efficiency, but the influence of the decrease in plasma temperature due to the heat of vaporization of the sample mist introduced into the plasma is reduced by removing the solvent, and the plasma is maintained at a high temperature. In the ICP-MS, when an element having a small influence of interfering molecular ions caused by Ar as a plasma gas or other elements having a high ionization potential is measured, if the measurement is performed under a high-temperature plasma condition (thermal plasma), the element (for example, Fe) having the small influence is greatly influenced by the interfering molecular ions. Therefore, in the quadrupole ICP-MS, as in patent document 2, although a method of selectively separating interfering molecular ions by using introduced ions through a collision/reaction cell is performed, the influence of the interfering molecular ions cannot be reduced in the ICP-MS not having a collision/reaction cell (for example, the quadrupole ICP-MS or the high-resolution ICP-MS not having such a cell mounted thereon).

Therefore, the following method is also performed: by reducing the high frequency power supplied to the plasma torch and generating plasma (cold plasma or low temperature plasma) at a lower temperature than usual, ionization of Ar or other elements having a higher ionization potential is suppressed, and generation of interfering molecular ions is suppressed.

However, most of the water in the sample mist is lost by the desolvation sample introducing device, and even in the measurement under the low-temperature plasma condition, the measurement is affected by interfering molecular ions caused by Ar or other elements having a high ionization potential due to insufficient decrease in the plasma temperature.

Prior art documents

Patent document

Patent document 1: japanese patent laid-open publication No. 2014-222178

Patent document 2: japanese patent laid-open publication No. 22017-15676

Disclosure of Invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide a sample analysis method and a sample introduction apparatus which can suppress generation of interfering molecular ions caused by an element having a high ionization potential when analyzing an element in a sample ionized by plasma by introducing a sample gas containing a sample mist from which a solvent is removed by heating and a carrier gas for transporting the sample mist into the plasma.

In order to achieve the above object, a sample analysis method according to one aspect of the present invention comprises

Introducing a sample gas containing a sample mist from which a solvent is removed by heating and a carrier gas for transporting the sample mist into plasma, analyzing elements in the sample ionized by the plasma, and analyzing

A carrier gas containing moisture, i.e., a water-containing gas, is added to a path for introducing the sample gas into the plasma.

In addition, a sample introduction device according to an aspect of the present invention is

Means for introducing said sample gas into said plasma and applying the following method: introducing a sample gas containing a sample mist from which a solvent is removed by heating and a carrier gas for transporting the sample mist into plasma, and analyzing elements in the sample ionized by the plasma; the sample introduction device is provided with:

a generation unit that generates a moisture-containing gas that is a carrier gas containing moisture; and

a path for adding the gas containing moisture generated in the generating section to a path for introducing the sample gas into the plasma.

According to one aspect of the present invention, since a carrier gas (water-containing gas) containing moisture is added to a path for introducing a sample gas containing a sample mist from which a solvent is removed by heating and a carrier gas for transporting the sample mist into plasma, the sample gas containing moisture is introduced into the plasma. Therefore, the temperature of the plasma is lowered by the energy consumption accompanying the vaporization heat of the water, and the ionization of the element having a high ionization potential is suppressed, so that the generation of interfering molecular ions caused by the element having a high ionization potential can be suppressed. In addition, the effect of desolvation (the effect of reducing the particle size of the mist of the sample and improving the efficiency of introducing the sample into the plasma) can be obtained.

The aqueous gas is generated by bubbling a carrier gas in ultrapure water, or may be generated by immersing a carrier gas line composed of a hollow fiber filter in ultrapure water. The ultrapure water is water having an extremely high purity and a specific resistance exceeding 15 M.OMEGA.cm.

In one aspect of the present invention, the plasma may be inductively coupled plasma generated with supply power of 550W to 700W. By setting the plasma generation condition to a low-temperature plasma condition in this way, the plasma temperature can be sufficiently lowered, and the generation of interfering molecular ions due to an element having a high ionization potential can be suppressed. Therefore, an element (for example, Fe) which is susceptible to the influence of interfering molecular ions due to an element having a high ionization potential can be accurately analyzed.

Drawings

FIG. 1 is a schematic diagram of an inductively coupled plasma mass spectrometer system according to embodiment 1.

FIG. 2 is a schematic diagram of an inductively coupled plasma mass spectrometer system according to embodiment 2.

FIG. 3 is a schematic diagram of an inductively coupled plasma mass spectrometer system according to a comparative example.

Fig. 4 is a graph comparing the lower limit value DL for Na detection and the background equivalent concentration BEC in the example and comparative examples 1 and 2.

Fig. 5 is a graph comparing the detection lower limit DL for Mg and the background equivalent concentration BEC in the example and comparative examples 1 and 2.

Fig. 6 is a graph comparing the detection lower limit DL for AI and the background equivalent concentration BEC in the example and comparative examples 1 and 2.

Fig. 7 is a graph comparing the detection lower limit DL for Ca and the background equivalent concentration BEC in the example and comparative examples 1 and 2.

Fig. 8 is a graph comparing the detection lower limit DL for Ti and the background equivalent concentration BEC in the example and comparative examples 1 and 2.

Fig. 9 is a graph comparing the lower limit value DL for Cr detection and the background equivalent concentration BEC in the example and comparative examples 1 and 2.

Fig. 10 is a graph comparing the detection lower limit DL for Mn and the background equivalent concentration BEC in the example and comparative examples 1 and 2.

Fig. 11 is a graph comparing the lower limit value DL for Fe detection and the background equivalent concentration BEC in the example and comparative examples 1 and 2.

Fig. 12 is a graph comparing the detection lower limit DL for Ni and the background equivalent concentration BEC in the example and comparative examples 1 and 2.

Fig. 13 is a graph comparing the lower limit value DL of detection for Cu and the background equivalent concentration BEC in the example and comparative examples 1 and 2.

Fig. 14 is a graph comparing the detection lower limit value DL for Zn and the background equivalent concentration BEC in the example and comparative examples 1 and 2.

Detailed Description

Embodiment 1

Hereinafter, embodiment 1 of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a system for analyzing an element in a sample by an inductively coupled plasma mass spectrometry. The system of fig. 1 includes: a sample introduction device 1; a plasma torch 30 for generating inductively coupled plasma for ionizing the introduced sample after the sample is introduced from the apparatus 1; and an analyzing device 40 for performing mass analysis of the sample (element) ionized by the plasma torch 30. First, the structure of the sample introduction device 1 will be described.

The sample introduction device 1 includes: a tube 3 which sucks a sample from a container 2 containing a liquid sample (sample solution); a nebulizer 4 that changes the sucked sample into a nebulized state (i.e., generates a sample mist); a gas pipe 5 for introducing a carrier gas (hereinafter, also referred to as a nebulizer gas) into the nebulizer 4; an MFC6 (mass flow controller) that controls the gas flow rate of the gas pipe 5; and a solvent removal part 7 for performing solvent removal treatment on the sample mist generated by the atomizer 4 by heating. Further, the sample introduction device 1 includes: a gas pipe 9 (hereinafter also referred to as a sample introduction pipe) for introducing the sample mist containing the desolvated solvent in the desolvation part 7 and the carrier gas sample gas introduced from the gas pipe 5 to the atomizer 4 into the plasma torch 30. And an addition unit 10 for adding a carrier gas containing water (hereinafter, also referred to as a water-containing gas) to the sample introduction tube 9.

The container 2 is made of, for example, a material having chemical resistance (e.g., a fluororesin such as PFA (tetrafluoroethylene-perfluoroalkoxyethylene copolymer resin)). The sample solution contained in the container 2 contains, for example, water, ethanol, hydrofluoric acid (hydrogen fluoride, HF), hydrogen peroxide water, and the like as a solvent.

The nebulizer 4 is a PFA coaxial type nebulizer, for example. The sprayer 4 may be a type other than a coaxial type. When the sample solution does not contain a substance having a strong corrosive action such as hydrofluoric acid, a glass nebulizer may be used as the nebulizer 4, or an ultrasonic nebulizer may be used as the nebulizer 4. The nebulizer gas is, for example, argon or nitrogen. The flow rate of the nebulizer gas is adjusted to a specific amount (for example, 0.60 to 1.00L/min) by MFC 6.

The desolvation part 7 is provided with: a heating chamber (e.g., a heating cyclone chamber) for heating the sample mist generated by the atomizer 4 and vaporizing a solvent contained in the sample; a cooling unit that cools the heated sample droplet and the vaporized solvent, and condenses the vaporized solvent; a pump for discharging the solvent condensed by the cooling part; and a drain pipe 8 for discharging the solvent to the outside in accordance with the operation of the pump. The desolvation part 7 can be a commercially available desolvation sample introducing device such as APEX (ESI) or DHS (IAS).

The desolvation unit 7 vaporizes the solvent in the sample droplet by heating the sample mist in the heating chamber, thereby miniaturizing the size of the sample droplet. In this case, the sample droplet and the vaporized solvent vapor can be screened for fineness, and the size of the sample droplet can be screened. The sample droplets and the solvent vapor are then condensed by cooling in the cooling section, and the droplets having a large size or the condensed solvent can be discharged through a drain discharge pipe 8 connected just below the cooling section. The particle size of the sample mist is reduced by the desolvation part 7, so that the sample mist can be carried on the carrier gas to be easily transported. The heating temperature in the heating chamber of the solvent removal section 7 is set to, for example, a temperature exceeding the boiling point of the solvent in the sample mist. The cooling temperature of the cooling section of the desolvation section 7 is set to, for example, a temperature in a range where the solvent does not solidify.

The sample introduction tube 9 has one end connected to the outlet of the desolvation part 7 and the other end connected to the inlet of the central tube of the plasma torch 30.

The addition unit 10 includes: a container 11 containing ultrapure water; a gas pipe 12 for supplying a carrier gas to the ultrapure water contained in the container 11; an MFC13 that controls the gas flow rate of the gas pipe 12; and a gas pipe 14 for supplying the gas (aqueous gas) in the container 11 to a position midway in the sample introduction pipe 9. The container 11 may be made of PFA, for example. The container 11 has a space 11a above the ultrapure water, which is not occupied by the ultrapure water.

The gas pipe 12 is provided in the form of one end immersed in ultrapure water in the container 11. The carrier gas (additive gas) supplied to the container 11 through the gas pipe 12 is, for example, the same gas as the gas of the nebulizer, but is not necessarily the same gas as the gas of the nebulizer. The additive gas is, for example, argon gas or nitrogen gas. The gas pipe 14 is provided separately from the gas pipe 12. One end of the gas pipe 14 is disposed in the space 11a in the container 11, and the other end is connected to the middle portion of the sample introduction pipe 9. The flow rate of the moisture-containing gas added from the addition unit 10 to the sample introduction tube 9 is adjusted to a specific amount (for example, 0.10 to 0.50L/min) by the MFC 13.

The above is the structure of the sample introduction device 1. Next, the structure of the plasma torch 30 and the analyzer 40 will be described. The plasma torch 30 has a triple tube structure in which a center tube, an auxiliary tube provided so as to cover the periphery (outside) of the center tube, and an outermost tube provided so as to cover the periphery (outside) of the auxiliary tube are arranged concentrically. Each tube of the plasma torch 30 is, for example, quartz glass (SiO)₂) Or heat-resistant glass (e.g., SiO)₂And B₂O₃Mixed borosilicate glass).

The sample gas from the sample introduction device 1 is introduced into the center tube. That is, the sample introduction tube 9 is connected to one end of the central tube in the axial direction. At the other end of the center tube, an opening is formed that communicates with the tip end portion of the outermost tube (a portion where an induction coil described later is provided and which is a space where inductively coupled plasma is generated).

A gas inlet is formed at one end of the auxiliary pipe. An assist gas is introduced from the gas inlet. The auxiliary gas is a gas for preventing the generated plasma from contacting the plasma torch 30, such as argon gas. The other end of the auxiliary tube is formed with an opening for discharging the introduced auxiliary gas to the tip end portion in the outermost tube. The flow rate of the assist gas is adjusted to a specific amount (for example, 0.6 to 1.5L/min) by an MFC (not shown).

A gas inlet is formed at one end side of the outermost tube. A plasma gas (e.g., argon gas) as a main plasma forming gas is introduced from the gas inlet. The flow rate of the plasma gas is adjusted to a specific amount (for example, 14.0 to 18.0L/min) by an MFC (not shown). Further, an induction coil is provided on the outer periphery of the tip end (end opposite to the gas inlet) of the outermost pipe. The induction coil is connected with a high-frequency power supply. The high frequency power applied to the induction coil is, for example, 550W to 700W under the low temperature plasma condition. An inductively coupled plasma is generated at the tip of the outermost tube by introducing a plasma gas into the outermost tube, introducing an auxiliary gas into the auxiliary tube, and applying a high frequency to the induction coil.

The analyzer 40 includes: an interface section composed of a sampling cone and a skimmer cone for extracting ions (samples) generated in the plasma of the plasma torch 30 into a vacuum system of the mass analyzer; an ion lens unit for efficiently guiding ions passing through the interface unit to the mass analyzer; a mass separation unit that mass-separates ions passing through the ion lens unit; an ion detection unit that detects the ions mass-separated by the mass separation unit; and a calculation unit for analyzing the data (mass spectrum) detected by the ion detection unit.

The above is the configuration of the system of fig. 1. Next, the operation of the system of fig. 1 will be described. The sample gas containing the sample mist generated in the nebulizer 4 and the carrier gas is introduced into the desolventizing section 7. The sample gas introduced into the desolvation portion 7 is heated and then cooled to desolvate the sample gas, thereby reducing the sample particle size. The sample carrier gas (in other words, the dried gas-sol sample) having a small particle size screened in the desolvation section 7 is introduced into the central tube of the plasma torch 30 through the sample introduction tube 9. At this time, the water-containing gas from the addition portion 10 is added to the sample introduction tube 9. That is, bubbling is performed by supplying a carrier gas to the ultrapure water in the container 11. The space 11a of the container 11 is filled with a carrier gas (water-containing gas) containing molecules (water) of ultrapure water after bubbling. The aqueous gas in the space 11a is added to the sample introduction tube 9 via the gas tube 14.

Thus, the sample gas containing moisture is introduced into the central tube of the plasma torch 30. The sample gas containing moisture introduced into the center tube is introduced into the center of the inductively coupled plasma generated at the tip of the plasma torch 30, and the sample is ionized. The ionized sample is introduced into the analyzing device 40 and mass-analyzed.

According to this embodiment, since moisture is introduced into the sample gas after the solvent removal and before the introduction of the plasma, the efficiency of introducing the sample into the plasma by the solvent removal is maintained, the temperature of the plasma can be sufficiently lowered by the energy consumption accompanying the vaporization heat of moisture, and the ionization of elements other than the analysis object having a high ionization potential can be suppressed, that is, the generation of interfering molecular ions can be suppressed. Therefore, as shown in the examples described later, the detection lower limit dl (detection limit) and the background Equivalent concentration bec (background Equivalent concentration) of the element to be analyzed can be improved. In particular, by adding the moisture-containing gas to the sample introduction tube 9, moisture can be introduced into the central tube of the plasma torch 30 together with the sample gas, and the temperature of the central portion of the plasma into which the sample gas is introduced can be effectively lowered. Therefore, generation of interfering molecular ions in the center portion of the plasma can be suppressed.

Further, by setting the plasma condition to a low-temperature plasma condition (a condition in which the supply power of the induction coil is set to 550W to 700W), the plasma temperature can be further reduced as compared with a high-temperature plasma condition (a condition in which the supply power exceeds 700W), and the generation of interfering molecular ions due to an element having a high argon plasma potential can be further suppressed. Therefore, an element to be analyzed (an element having a mass close to that of the interfering molecular ion) which is susceptible to the influence of the interfering molecular ion by the element having a high ionization potential can be analyzed with high sensitivity.

Embodiment 2

Next, the differences between embodiment 2 and embodiment 1 of the present invention will be mainly described. Fig. 2 shows the structure of the inductively coupled plasma mass spectrometer system according to this embodiment. In fig. 2, the same components as those in fig. 1 are denoted by the same reference numerals. The system of fig. 2 is the same as the system of fig. 1 except that the configuration of the addition unit 15 is different from that of the addition unit 10 of fig. 1.

The addition unit 15 of fig. 2 includes: a container 11 containing ultrapure water; a gas pipe 16; and an MFC18 that controls the gas flow rate of the gas pipe 16. The container 11 is constructed in the same manner as in fig. 1. The gas pipe 16 is formed in a shape in which an upstream portion for introducing gas into the container 11 and a downstream portion for discharging gas from the container 11 are connected. Specifically, the gas pipe 16 is formed of a pipe body of a hollow fiber membrane (hollow fiber filter) and is provided in a state of being immersed in ultrapure water in the container 11, in a part 17 thereof. The hollow fiber filter unit 17 is configured to allow a certain amount of water molecules in the ultrapure water to penetrate into the hollow fiber filter unit 17 through the wall surface of the hollow fiber filter unit 17. At this time, the amount of water penetrating the hollow fiber filter unit 17 or the particle diameter is adjusted by the hollow fiber filter unit 17 so that the water permeating the hollow fiber filter unit 17 is carried on the carrier gas and is transported.

An upstream portion of the gas pipe 16 (a gas pipe portion for supplying the carrier gas to the container 11) is connected to one end of the hollow fiber filter portion 17, and a downstream portion of the gas pipe 16 (a gas pipe portion for guiding the aqueous gas from the container 11 to the sample introduction pipe 9) is connected to the other end of the hollow fiber filter portion 17. The end of the downstream portion of the gas pipe 16 is connected to the sample introduction pipe 9. The MFC18 is provided at the upstream portion of the gas pipe 16. The portion of the gas pipe 16 other than the portion 17 immersed in ultrapure water is formed of a material of a normal gas pipe (a material through which molecules cannot pass between the inside and the outside of the pipe). A carrier gas such as argon gas flows through the gas pipe 16.

To explain the operation of the addition unit 15, the carrier gas flowing through the gas pipe 16 is supplied with water from ultrapure water in the hollow fiber filter unit 17. Then, a carrier gas containing moisture is added to the sample introduction tube 9. Thus, the system of fig. 2 can also obtain the same operational effects as those of fig. 1.