TW201833363A - Plasma cone for inductively coupled plasma mass spectrometer, inductively coupled plasma mass spectrometer, and method for manufacturing plasma cone for inductively coupled plasma mass spectrometer - Google Patents

Abstract

A sampling cone (14) and a skimmer cone (16) as a plasma cone constituting part of an interface part of an inductively coupled plasma mass spectrometer have: base materials (141), (161) formed using copper, nickel, etc.; and coating films (142), (162) formed on the surface of the base materials (141), (161). The coating films (142), (162) are formed from platinum, a platinum group metal other than platinum, gold, or an alloy of these. Also, the coating films (142), (162) are formed using an ion plating method or a plasma CVD method. There are thereby provided a plasma cone, an inductively coupled plasma mass spectrometer comprising said plasma cone, and a method for manufacturing the plasma cone thereof, with which it is possible to reduce the impurity background and also improve durability without sacrificing sensitivity (ionic strength).

Description

 Plasma cone for inductively coupled plasma mass spectrometer, inductively coupled plasma mass spectrometer, and plasma cone for inductively coupled plasma mass spectrometer  

The present invention relates to a plasma cone for use in an inductively coupled plasma mass spectrometer, an inductively coupled plasma mass spectrometer having the same, and a method of manufacturing a plasma cone.

Inductively Coupled Plasma Mass Spectrometer (hereinafter sometimes referred to as ICPMS) is a device that supplies high frequency power to an induction heating coil placed in a plasma torch portion to generate an inductive plasma. The aerosolized sample solution is sprayed to the center of the plasma to ionize the elements contained in the sample. The ions are introduced into the vacuum system via the plasma interface, and are separated into target masses by a mass spectrometer, and then counted by a detector, whereby identification or quantification of ions (elements) can be performed. The ICPMS is characterized in that multi-element analysis can be performed simultaneously with high sensitivity, and the calibration curve has a wide range of straight lines.

The ICPMS is composed of a sample introduction portion that introduces a sample solution as a spray, a plasma torch portion that ionizes an element contained in the sprayed sample, and a face portion that introduces ions to have A vacuum system of a mass spectrometer; an ion lens portion for efficiently guiding ions to a mass spectrometer; a mass separation portion for mass separation of ions; and an ion detecting portion for detecting ions.

Among them, the interface is composed of two kinds of plasma cones (sampling cones and intercepting cones) with small holes in the center. As a good thermal conductivity, strong and high corrosion resistance, there are also materials mainly made of nickel or copper. Only platinum is used at the front end (see Figure 4).

Since the plasma cone is in direct contact with the plasma as the ionization source, the material used therein is also ionized. If the material used in the plasma cone is ionized, it becomes background noise and cannot be distinguished from the ions actually contained in the sample. As a countermeasure against this, Patent Document 1 discloses that the entire plasma cone is formed of platinum.

[Previous Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. Hei 8-115702

Platinum is a metal that is excellent in thermal conductivity and is strong and has high corrosion resistance. It is considered that if a plasma cone is formed by platinum, the background rise of nickel or copper can be suppressed, and the life of the plasma is longer than that of nickel or copper. However, it has been found that there is a problem that the sensitivity (ion strength) is inferior to the nickel or copper plasma cone. ICPMS is a device characterized by high-sensitivity analysis. Poor sensitivity will sacrifice device performance and is therefore poor.

The present invention has been made in view of the above problems, and an object thereof is to provide a plasma cone which can reduce the background of impurities without sacrificing sensitivity (ion strength), and an inductively coupled plasma mass spectrometer having the same, and the plasma The manufacturing method of the cone.

In order to solve the above problems, the plasma cone for an inductively coupled plasma mass spectrometer of the present invention is characterized in that a coating film of a platinum group metal other than platinum or platinum or an alloy of gold or the like is provided on the surface. Further, the inductively coupled plasma mass spectrometer of the present invention comprises a plasma cone having a coating film of a platinum group metal other than platinum or platinum or an alloy of gold or the like.

Thus, by forming a coating film of a platinum group metal such as platinum or platinum or an alloy of gold or the like on the surface of the plasma cone, the impurity background can be reduced without sacrificing sensitivity (ionic strength), and the durability of the plasma cone can be improved. Sex. Further, the platinum group metal other than platinum means ruthenium, rhodium, palladium, iridium or osmium. Further, the coating film is preferably formed of platinum.

Further, the coating film is preferably formed by an ion plating method or a plasma CVD method. Thereby, a high-quality coating film can be formed as compared with the case of using a method other than the ion plating method or the plasma CVD method.

100‧‧‧Inductively coupled plasma mass spectrometer

7‧‧‧ facial

14‧‧‧Sampling cone (plasma cone)

16‧‧‧ interception cone (plasma cone)

Figure 1 is a block diagram of an inductively coupled plasma mass spectrometer.

2 is a cross-sectional view of a plasma torch portion and a face portion (sampling cone, intercepting cone) of an inductively coupled plasma mass spectrometer.

Figure 3A is a side elevational view of the sampling cone of the embodiment.

Figure 3B is a side elevational view of the intercepting cone of the embodiment.

4A is a side view of the sampling cone of Comparative Example 1.

4B is a side view of the intercepting cone of Comparative Example 1.

Fig. 5A is a side view of the sampling cone of Comparative Example 2.

Fig. 5B is a side view of the intercepting cone of Comparative Example 2.

Hereinafter, embodiments of the present invention will be described. Fig. 1 shows the configuration of an ICPMS 100 of this embodiment. In the ICPMS 100, the sample solution 1 is introduced into the introduction portion 2 as a spray, vaporized there, and introduced into the plasma of the plasma torch portion 4 by a carrier gas 3 such as argon gas. Here, for example, argon gas 5 is introduced into the plasma torch portion 4, and argon plasma is generated by applying electric power from the high-frequency power source 6. At this time, the vaporized sample is heated to, for example, 8000 to 10000 K in the plasma to be ionized.

Thereafter, the ionized sample is introduced into the dielectric surface portion 7 composed of the two types of plasma cones, which are shown by the sampling cone 14 and the intercepting cone 16, as shown in FIG. 2, and is introduced into the high vacuum by the differential exhaust gas 9. Inside the vacuum chamber 8. The ions introduced into the vacuum chamber 8 are subjected to energy focusing by the ion lens unit 10, and mass separation and detection are performed by the mass spectrometer 11. The data (mass spectrum) detected by the mass spectrometer 11 is transmitted to the arithmetic unit 12, and the arithmetic unit 12 performs analysis processing.

Here, the sampling cone 14 and the cutting cone 16 shown in FIG. 2 are each tapered (conical), and holes 143 and 163 having small diameters are formed at the tip end thereof. The holes 143 and 163 are disposed at positions opposed to the plasma from the torch unit 4. Further, when viewed from the torch unit 4, the sampling cone 14 and the cutting cone 16 are arranged in this order. The sample ionized in the torch portion 4 is bundled by the sampling holes 14 and the center holes 143 and 163 of the cutting cone 16, and is introduced into the vacuum chamber 8.

Further, the sampling cone 14 and the cutting cone 16 have a base material 141, 161 formed in a tapered shape, and a coating film 142 formed on the surface of the base material 141, 161 (the outer surface facing the side of the plasma torch portion 4). 162. The base materials 141 and 161 are formed of a metal other than a platinum group metal, gold, or the like, at least in addition to the tip end, and are specifically formed of, for example, copper, nickel, aluminum, or the like. Further, the front ends of the base materials 141 and 161 may be formed of a metal other than a platinum group metal, gold, or the like (copper, nickel, aluminum, or the like), or may be formed of a platinum group metal, gold, or the like.

On the other hand, the coating films 142 and 162 are formed of a platinum group metal having a corrosion resistance superior to that of copper or nickel, or an alloy of gold or the like, and are preferably formed of platinum excellent in corrosion resistance. The coating films 142 and 162 are formed so as to cover the entire outer surfaces of the base materials 141 and 161. Further, the coating films 142 and 162 may be formed on the inner surface (back surface) of the base materials 141 and 161, or may be formed on the inner surface (back surface) of the base materials 141 and 161.

The coating films 142 and 162 are preferably formed by an ion plating method or a plasma CVD (Chemical Vapor Deposition) method. Thereby, as shown in the following examples, high-quality coating films 142, 162 can be obtained.

Thus, since the surface of the plasma cones 14, 16 has a coating film 142, 162 of a platinum group metal or an alloy of gold or the like, as shown in the following examples, the impurity background can be lowered without sacrificing sensitivity (ionic strength). The durability of the plasma cones 14, 16 can be improved.

[Examples]

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto.

(Example 1)

The device used for the evaluation was a plasma cone of the plasma cone (Comparative Example 1) and FIG. 5A and FIG. 5B of FIG. 4A and FIG. 4B, respectively, using a high-resolution inductively coupled plasma mass spectrometer ELEMENT2 manufactured by Thermo Fisher Scientific. (Comparative Example 2) and the comparison of the ionic strength, the ionic strength ratio, and the detection lower limit value in the plasma cone (Example) of Figs. 3A and 3B. Here, the plasma cone (sampling cone 24, intercepting cone 25) of FIGS. 4A and 4B has a nickel (Ni) plating layer 21 on the surface of the copper (Cu) base material 20, and further has a front end of the copper base material 20 Platinum (Pt) tip 22 construction. Further, the plasma cones (the sampling cone 26 and the cutting cone 27) of Figs. 5A and 5B are all formed of platinum 28. Further, the plasma cone (sampling cone 18, intercepting cone 19) of FIGS. 3A and 3B is a platinum coating film of 20 μm deposited on the surface of the plasma cones 24 and 25 of FIGS. 4A and 4B by ion plating. Made of structure. Further, in FIGS. 3A, 3B, 4A, and 4B, the tip end of the platinum tip 22 is indicated by hatching.

A blank sample solution obtained by diluting ultrapure water in a manner of 5 wt% (% by weight) of Tama Chemical-made ultra-high purity nitric acid (TAMAPURE-AA-100), and In, Na, in the same solution The standard solution prepared by the method of the concentration of each of Mg, Al, Ca, Cr, Fe, Ni, Cu, and Zn is 0.1 ppb, and the plasma cones 18, 19, 24, 25, 26 of FIGS. 3 to 5 are compared. The background ionic strength of Na, Mg, Al, Ca, Cr, Fe, Ni, Cu, Zn and the ionic strength of In in 27. The results are shown in Table 1. In Table 1, the background ionic strength of Na, Mg, Al, Ca, Cr, Fe, Ni, Cu, Zn shows the result of the blank sample solution, and the ionic strength of In shows the standard solution of In of 0.1 ppb. result. The results of Table 1 show the average of the results of a plurality of measurements obtained by performing multiple ion intensity measurements using a blank sample solution and a standard solution, respectively.

Further, the ratio of the ionic strength of each element (Na, Mg, Al, Ca, Cr, Fe, Ni, Cu, Zn) other than In in Table 1 to the ionic strength of In was determined. The results are shown in Table 2.

Further, using the blank sample solution and the standard solution, a calibration curve indicating the relationship between the ion intensity and the concentration was prepared for each of the elements (Na, Mg, Al, Ca, Cr, Fe, Ni, Cu, and Zn). Further, the ionic strength of each element when the blank sample solution is used is measured a plurality of times, and the concentration corresponding to 3σ (three times the standard deviation σ) among the obtained measurement results is calculated as the detection lower limit value of each element. . The detection lower limit is calculated based on the calibration curve. Since the ionic strength of each element when the blank sample solution is used is background noise, the ionic strength in the range of 3σ including 99.7% of the background noise is excluded from the detectable concentration, and the upper limit of the range is The ionic strength above the value (ie, 3σ) is taken as the detectable concentration. The calculation results of the detection lower limit value are shown in Table 3.

As shown in Table 1, it is understood that in the plasma cones 18 and 19 of the embodiment of Figs. 3A and 3B, the ionic strength of In is substantially higher than that of the plasma cones 24 and 25 of Comparative Example 1 of Figs. 4A and 4B. Similarly, in contrast, the ionic strength (background ionic strength) of Na, Mg, Al, Ca, Cr, Fe, Ni, Cu, and Zn is decreased. The reason for this is considered to be that, in the plasma cones 18 and 19 of the embodiment, since the surface of the base material 20 is covered with platinum 23, evaporation of elements due to the base material 20 can be prevented. For the same reason, it is understood that the ratio of the ionic strength of each element to the In intensity is also small (see Table 2), and the detection lower limit is also improved (refer to Table 3).

On the other hand, in the plasma cones 26 and 27 of Comparative Example 2 of FIGS. 5A and 5B, the background ion intensity was reduced as compared with the plasma cones 24 and 25 of Comparative Example 1 of FIGS. 4A and 4B. The ionic strength of In was reduced to about 1/20 (refer to Table 1), and the ratio of the ionic strength of each element to the In intensity was inversely increased (refer to Table 2), and the detection lower limit was also deteriorated (refer to Table 3).

Thus, in the embodiment, the ionic strength (sensitivity) can be maintained and the increase in the background of the impurities caused by the material of the plasma cone can be prevented, and the improvement of the detection lower limit can be achieved.

(Example 2)

When a platinum film is formed on the surface of a plasma cone by various coating methods (specifically, ion plating method, vacuum vapor deposition method, sputtering vapor deposition method, plasma CVD method, or electrolytic plating method), investigation is conducted. The degree of adhesion of each platinum film to the base material, the film density, and the contamination of the impurities during film formation. Further, the structure of the base material of the plasma cone is the structure of FIG. 4A and FIG. 4B (the structure having the nickel plating layer 21 on the surface of the copper base material 20 and having the platinum tip 22 at the front end). The results of the survey are shown in Table 4.

As shown in Table 4, it is understood that when the platinum film is formed by the ion plating method, the adhesion, the film density, and the degree of impurity contamination during film formation are all good (○), and it is particularly preferable as a coating method of the platinum film. It is an ion plating method.

Further, in the plasma CVD method, the adhesion is slightly inferior (Δ) as compared with the ion plating method, but the film density and the degree of impurity contamination during film formation are good (○), and the plasma CVD method is used as the platinum film. The coating method is also preferred.

(Example 3)

The plasma cones 18 and 19 of FIG. 3A and FIG. 3B are investigated (the plasma cones 24 and 25 of FIGS. 4A and 4B are deposited with 20 μm of platinum 23), and the plasma cones 24 and 25 of FIG. 4A and FIG. The durability (life) of each of the nickel base layer 21 on the surface of the copper base material 20 and the plasma cone of the platinum tip 22 at the tip end. The results are shown in Table 5.

As shown in Table 5, the conventional plasma cone (the plasma cones 24 and 25 of Figs. 4A and 4B) has a durability of about 3 months. In contrast, a plasma cone having a platinum coating (Fig. 3A, The durability of the plasma cones 18, 19) of Fig. 3B is 6 months to 8 months, which is approximately twice the durability of the conventional plasma cone. Thus, it can be seen that the durability of the plasma cone can be improved by the fact that the surface coating corrosion resistance is superior to that of copper or nickel.

Furthermore, the present invention is not limited to the above embodiment. The above-described embodiments are exemplified, and those having substantially the same configuration as the technical idea described in the patent application of the present invention and exerting the same effects are included in the technical scope of the present invention. 3A and 3B, a configuration in which a coating film 23 of platinum is formed on the surface of the plasma cones 24 and 25 of FIGS. 4A and 4B is exemplified as an embodiment of the present invention, but may be employed in FIG. 5A. The composition of the coating film of the platinum group metal or the alloy of gold or the like is formed on the surface of the plasma cones 26 and 27 of FIG. 5B (that is, the base material is entirely formed of platinum, and is formed on the surface of the platinum base material. The composition of the coating film). Thereby, the sensitivity equivalent to the case of using the plasma cones 26 and 27 of FIGS. 5A and 5B can be achieved, and the background of the impurities generated by the platinum base material can be reduced, and the durability can be improved.

Claims (4)

 A plasma cone for an inductively coupled plasma mass spectrometer having a coating film of a platinum group metal other than platinum or platinum or an alloy of gold or the like on the surface.    A plasma cone for an inductively coupled plasma mass spectrometer according to the first aspect of the invention, wherein the coating film is formed of platinum.    An inductively coupled plasma mass spectrometer having a plasma cone for an inductively coupled plasma mass spectrometer of claim 1 or 2.    A method for manufacturing a plasma cone for an inductively coupled plasma mass spectrometer, which comprises forming a coating film having a platinum group metal other than platinum or platinum or an alloy of gold or the like on the surface by ion plating or plasma CVD. The above coating film for a plasma cone of a plasma mass spectrometer.