JPWO2019054325A1 - Mass spectrometry method and mass spectrometer - Google Patents

Abstract

Provided is a mass spectrometer capable of easily separating target ions and interfering ions having the same mass-to-charge ratio m / z. The mass spectrometer includes a QMS1 that separates target ions and interference ions having similar mass-to-charge ratios from various ions into a reaction cell according to the mass-to-charge ratio, and a reaction cell into which the target ions and the interference ions are introduced. And an ozone generator for supplying ozone to the reaction cell, and a target ion product generated by the reaction of the target ion with ozone in the reaction cell, QMS2 and QMS2 separated from interfering ions according to the mass-to-charge ratio. It has a detector that measures the signal intensity of the target ion product separated by.

Description

  The present invention relates to mass spectrometry, a type of chemical analysis technique.

  The mass spectrometry is a technique for performing analysis based on the ratio between the mass number m and the charge z of the target ion to be analyzed, that is, the mass-to-charge ratio m / z. Non-target ions having the same mass-to-charge ratio as target ions are interfering ions. In order to analyze a target ion accurately, interference of a non-target ion must be removed. If a high-resolution mass spectrometer is used, target ions can be separated from interfering ions. However, when the mass-to-charge ratio of the target ion and the interfering ion is slightly different, it is difficult to separate them even with a high-resolution mass spectrometer.

In the reaction cell technology or the collision cell technology, target ions can be separated from interference ions by reacting target ions or interference ions with reaction gas molecules to convert the target ions or interference ions into another substance. For example, when the target ion is ³² S ⁺ and the interference ion is ¹⁶ O ₂ ⁺ , both have a mass-to-charge ratio of 32. Therefore, in the coexistence of ³² S ⁺ and ¹⁶ O ₂ ⁺ , ³² S ⁺ is reacted with ¹⁶ O ₂ to convert ³² S ⁺ to ³² S ¹⁶ O ⁺ . Then, if ³² S ¹⁶ O ⁺ is separated from ¹⁶ O ₂ ⁺ based on the mass-to-charge ratio of 48 and 32, the target ion can be accurately analyzed. In the reaction cell technology, a higher separation effect can be obtained than in a high-resolution mass spectrometer. However, in the reaction cell technology, sufficient reactivity may not be obtained by using an existing reaction gas. For example, according to Non-Patent Document 1, Ba ⁺ and O ₂ do not react.

Gas-phase ion-molecule reactions for resolution of atomic isobars: AMS and ICP-MS perspectives, International Journal of Mass Spectrometry, 2006, 255-256, p.312-327

  The present invention has been made in view of such circumstances, and reacts an activated reaction gas with a target ion or an interference ion, separates the target ion from the interference ion, and performs accurate analysis of the target ion. An object of the present invention is to provide a mass spectrometry method and a mass spectrometer that can be used.

  The mass spectrometer of the present invention has a reaction cell into which target ions and interference ions are introduced, an ozone generation unit connected to the reaction cell, and a target ion product generated by reaction of target ions with ozone in the reaction cell. , A mass separation unit that separates the interference ions according to the mass-to-charge ratio, and a measurement unit that measures the signal intensity of the target ion product separated by the mass separation unit.

  Another mass spectrometer according to the present invention includes a reaction cell into which target ions and interference ions are introduced, an ozone generator connected to the reaction cell, and target ions, which are interfering ions in the reaction cell according to a mass-to-charge ratio. Has a mass separation unit that separates from interference ion products generated by reacting with ozone, and a measurement unit that measures the signal intensity of target ions separated by the mass separation unit.

  The mass spectrometry method of the present invention comprises the steps of: supplying ozone to a target ion and an interference ion to obtain a target ion product which is a reaction product of the target ion and ozone; and And a measurement step for measuring the signal intensity of the target ion product separated in the mass separation step.

  Another mass spectrometry method of the present invention comprises the steps of: supplying ozone to a target ion and an interference ion to obtain an interference ion product which is a reaction product of the interference ion and the ozone; and The method includes a mass separation step of separating an ion product from a target ion, and a measurement step of measuring a signal intensity of the interference ion product separated in the mass separation step.

  According to the present invention, in mass spectrometry, target ions having a mass-to-charge ratio similar to that of interference ions can be separated from interference ions with high accuracy.

1 is a principle diagram of a mass spectrometer according to an embodiment of the present invention. 3 is a graph showing the signal intensity of Ba ions and Ba ion products with respect to mass-to-charge ratio (Example 1). 4 is a graph showing the signal intensity of Cs ions and Cs ion products with respect to the mass-to-charge ratio (Example 2). 9 is a graph showing the signal intensity of Sr ions and Sr ion products with respect to the mass-to-charge ratio (Example 3). 9 is a graph showing the signal intensity of Rb ions and Rb ion products with respect to the mass-to-charge ratio (Example 4). 13 is a graph showing the ratio of the signal intensity of MO ^{+ to} the signal intensity of M ⁺ (Example 5).

  FIG. 1 shows the principle of a mass spectrometer according to an embodiment of the present invention. This mass spectrometer includes an ion lens, a QMS1 as a first mass separation unit, a reaction cell, an ozone generator as an ozone generation unit, a QMS2 as a second mass separation unit, and a measurement unit. It has a detector. The ion lens converges various ions and introduces them into the QMS1. The QMS 1 separates target ions and interference ions having the same mass-to-charge ratio from various ions according to the mass-to-charge ratio m / z, and introduces them into the reaction cell.

The target ion and the interference ion separated by the QMS 1 are introduced into the reaction cell. The ozone generator is connected to the reaction cell, converts the oxygen gas O ₂ taken into ozone O ₃ and supplies it to the reaction cell. In the reaction cell, target ions react with O ₃ to generate target ion products. Note that the target ion product may include an element other than the target ion and oxygen. For example, when the target ion ¹³⁸ Ba ⁺ (m / z = 138) reacts with O ₃ , ¹³⁸ Ba ¹⁶ O ¹ H ⁺ (m / z = 155) or ¹³⁸ Ba ¹⁴ N ¹⁶ O ₃ ⁺ (m / z = 200) ) Is obtained. As described above, H and N inevitably present in the reaction cell can also be constituent elements of the target ion product.

Even if O ₂ is supplied to the reaction cell but hardly reacts with the target ion, by supplying O ₃ to the reaction cell, the target ion reacts with O ₃ to obtain a target ion product. The ozone generator may take in nitrogen gas N ₂ and O ₂ and supply NO _x to the reaction cell. It is considered that NO _x also reacts with one of the target ion and the interference ion to change the mass-to-charge ratio of the one ion. Examples of combinations of the target ion and the interference ion having the same mass-to-charge ratio include Cs ion and Ba ion, Ba ion and Cs ion, Sr ion and Rb ion, and Rb ion and Sr ion. In QMS2, target ion products are separated from interfering ions according to the mass-to-charge ratio. The detector measures the signal intensity of the target ion product separated by QMS2. The mass spectrometer according to the present embodiment may be manufactured by connecting an ozone generator to a reaction cell of a normal mass spectrometer.

In this embodiment, the target ion and the interference ion having the same mass-to-charge ratio are present in the reaction cell, and the target ion is reacted with O ₃ in the reaction cell to obtain a target ion product. Then, the target ion, that is, the target ion product whose mass-to-charge ratio is largely different from that of the interference ion, is separated from the interference ion according to the mass-to-charge ratio, and the signal intensity of the separated target ion product is measured. By doing so, the target ion is analyzed. Alternatively, the interference ion is reacted with O ₃ in the reaction cell to obtain an interference ion product, and the mass charge is changed from the interference ion, that is, the interference ion product having a mass-to-charge ratio that is largely different from that of the target ion. The target ions may be separated according to the ratio, and the separated target ions may be analyzed.

  That is, the mass spectrometer according to another embodiment of the present invention includes a reaction cell into which target ions and interference ions are introduced, an ozone generator that is an ozone generator that supplies ozone to the reaction cell, and target ions, In accordance with the mass-to-charge ratio, QMS2, which is a mass separation unit that separates interference ions generated by reaction of interference ions with ozone in the reaction cell, and measurement for measuring the signal intensity of target ions separated by QMS2 And a detector having a section.

  The mass spectrometry method according to the embodiment of the present invention may or may not use the mass spectrometer of each embodiment. The mass spectrometry method of the present embodiment includes a reaction step, a mass separation step, and a measurement step. In the reaction step, ozone is supplied to the target ion and the interference ion to obtain a target ion product which is a reaction product of the target ion and ozone. In the mass separation step, the target ion product is separated from the interference ions according to the mass-to-charge ratio. In the measurement step, the signal intensity of the target ion product separated in the mass separation step is measured. When the mass spectrometer of each embodiment is used, the reaction step, the mass separation step, and the measurement step are performed in the reaction cell, the QMS 2, and the detector, respectively.

Instead of this method, ozone is supplied to the target ion and the interference ion to obtain an interference ion product which is a reaction product of the interference ion and the ozone, and the target ion is converted from the interference ion product according to the mass-to-charge ratio. The signal strength of the separated target ions may be measured. In the mass spectrometry method of the present embodiment, one of the target ion and the interference ion having the same mass-to-charge ratio is caused to react with O _3, and the mass-to-charge ratio of the other is greatly changed. Can be separated. Therefore, it is possible to analyze the target ion in a state where the interference ion is hardly mixed with the target ion.

Example 1
O ₃ was supplied to a reaction cell of an inductively coupled plasma tandem quadrupole mass spectrometer (ICP-QMS / QMS) (Agilent, Inc., Agilent-8800 type ICP-QMS / QMS device) as shown in FIG. Elemental analysis was performed as follows. The QMS1 was set so that ions of m / z = 138 passed, and the QMS2 was set so that ions of m / z = 2 to 260 passed. A barium standard solution for mass spectrometry and nitric acid were mixed to prepare a sample solution containing barium at 1 mg / kg and nitric acid at 2% by mass.

The sample liquid was charged into the apparatus while supplying a reaction gas containing O ₃ or O ₂ to the reaction cell at 1.0 mL / min. The reaction gas containing O ₃ is obtained by supplying O ₂ to an ozone generator to reduce the concentration of O ₃ to about 10% by mass. That is, a reaction gas containing _{O 3} is the _{O 3} of about 10% to about 90% by weight of a mixed gas of _{O 2.} By switching between operation and non-operation of the ozone generator, a mixed gas of O ₃ and O ₂ (hereinafter sometimes simply referred to as “O ₃ ” in Examples 1 to 4) or O _{2 in} the reaction cell. Only (hereinafter sometimes simply referred to as “O ₂ ” in Examples 1 to 4).

FIG. 2 shows the signal intensity measured by the detection unit. FIG. 2 shows a value obtained by subtracting the signal intensity of the 2% by mass nitric acid aqueous solution. Further, in FIG. 2, m / z having a high signal strength is selected from m / z = 2 to 260. These are the same in the second to fourth embodiments. As shown in FIG. 2, when O ₂ was supplied, a high signal intensity of ¹³⁸ Ba ⁺ (m / z = 138) was observed. On the other hand, when O ₃ was supplied, the signal intensity of ¹³⁸ Ba ⁺ (m / z = 138) was considerably reduced. This is probably because O ₃ has high reactivity.

As described below, ¹³⁸ Ba ⁺ (m / z = 138) introduced into the reaction cell reacted with O ₃ to generate a Ba ion product, and the mass-to-charge ratio changed significantly.
¹³⁸ Ba ⁺ → ¹³⁸ Ba ¹⁶ O ⁺ (m / z = 154)
¹³⁸ Ba ⁺ → ¹³⁸ Ba ¹⁶ O ¹ H ⁺ (m / z = 155)
¹³⁸ Ba ⁺ → ¹³⁸ Ba ¹⁴ N ¹⁶ O ₃ ⁺ (m / z = 200)
^{138 Ba + → 138 Ba 14 N} 16 O 5 1 H + (m / z = 218)

Example 2
The elemental analysis of the sample solution containing the cesium standard solution was performed in the same manner as in Example 1 except that QMS1 was set so that ions of m / z = 133 passed. The result is shown in FIG. As shown in FIG. 3, a high signal intensity of ¹³³ Cs ⁺ (m / z = 133) was observed regardless of whether O ₃ or O ₂ was supplied. On the other hand, at other mass-to-charge ratios, the signal intensity was extremely low.

According to Example 1 and Example 2, Ba ion reacted with O ₃ to become a Ba ion product, and the mass-to-charge ratio changed greatly, whereas Cs ion hardly reacted with O ₃ and the mass charge ratio changed. The ratio did not change. Therefore, if O ₃ is supplied to a reaction cell in which Ba ions and Cs ions having similar mass-to-charge ratios are mixed, the mass-to-charge ratio of Ba ions changes greatly, and can be separated from Cs-ions according to the mass-to-charge ratio. . By analyzing the separated Ba ion product, an analysis result of Ba ion containing almost no Cs ion can be obtained. Alternatively, the Cs ion may be separated from the Ba ion product to obtain an analysis result of the Cs ion containing almost no Ba ion. In addition, it was confirmed that even when O ₂ was supplied to the reaction cell, Ba ions and Cs ions could not be accurately separated according to the mass-to-charge ratio.

Example 3
A sample solution containing a strontium standard solution was subjected to elemental analysis in the same manner as in Example 1 except that QMS1 was set so that ions of m / z = 88 passed. FIG. 4 shows the results. As shown in FIG. 4, when O ₂ was supplied, a high signal intensity of ⁸⁸ Sr ⁺ (m / z = 88) was observed. On the other hand, when O ₃ was supplied, the signal intensity of ⁸⁸ Sr ⁺ (m / z = 88) was considerably reduced. It was found that ⁸⁸ Sr ⁺ reacted with O ₃ to become an Sr ion product, and the mass-to-charge ratio changed significantly.

Example 4
The elemental analysis of the sample solution containing the rubidium standard solution was performed in the same manner as in Example 1 except that QMS1 was set so that ions of m / z = 85 passed therethrough. The result is shown in FIG. As shown in FIG. 5, a high signal intensity of ⁸⁵ Rb ⁺ (m / z = 85) was observed regardless of whether O ₃ or O ₂ was supplied. On the other hand, at other mass-to-charge ratios, the signal intensity was extremely low.

According to Examples 3 and 4, Sr ions react with O ₃ to form Sr ion products, and the mass-to-charge ratio changes greatly, whereas Rb ions hardly react with O ₃ and have a large mass-to-charge ratio. The ratio did not change. Therefore, if O ₃ is supplied to a reaction cell in which Sr ions and Rb ions having similar mass-to-charge ratios are mixed, the mass-to-charge ratio of the Sr ions changes greatly, and can be separated from Rb ions according to the mass-to-charge ratio. . By analyzing the separated Sr ion product, an analysis result of Sr ion containing almost no Rb ion can be obtained. The Rb ion may be separated from the Sr ion product to obtain an Rb ion analysis result containing almost no Sr ion. In addition, it was confirmed that even when O ₂ was supplied to the reaction cell, Sr ions and Rb ions could not be accurately separated according to the mass-to-charge ratio.

Example 5
An N ₂ introduction pipe was connected to a reaction gas introduction pipe between the ozone generator and the reaction cell of the mass spectrometer shown in FIG. O ₂ was supplied to the ozone generator at a flow rate of 0.35 mL / min, and N ₂ was supplied to the reaction gas introduction pipe at a flow rate of 0.7 mL / min. When the ozone generator was operated, a mixed gas of O ₃ , O ₂ , and N ₂ (hereinafter sometimes simply referred to as “O ₃ ” in this example) was introduced into the reaction cell, and the ozone generator was turned on. When not operating, a mixed gas of O ₂ and N ₂ (hereinafter sometimes simply referred to as “O ₂ ” in this example) was introduced into the reaction cell.

While supplying O ₃ or O ₂ to the reaction cell, a sample containing each element ion M ⁺ of ⁵² Cr ⁺ , ⁵⁵ Mn ⁺ , ⁵⁶ Fe ⁺ , ⁵⁹ Co ⁺ , ⁶⁰ Ni ⁺ , ⁷² Ge ⁺ , or ⁷⁷ Se ^+. The liquid was charged into this apparatus, and M ⁺ was introduced into the reaction cell via QMS1. Regardless of whether O ₃ or O ₂ was supplied to the reaction cell, a part of M ⁺ became oxide ion MO ^{+ in} the reaction cell. That is, for example ⁵² Cr ⁺ part of becomes ⁵² Cr ¹⁶ O ^+. Then, the signal intensities of M ⁺ and MO ⁺ passed through QMS2 were measured by the detectors.

For each element M, the ratio of the signal intensity of MO ⁺ to the measured ^{M +} signal intensity at the detector, i.e., wherein the MO ⁺ signal strength / ^{M +} signal strength (hereinafter simply ^"MO + / ^{M +"} Are shown in FIG. MO ⁺ indicates ⁵² Cr ¹⁶ O ⁺ , ⁵⁵ Mn ¹⁶ O ⁺ , ⁵⁶ Fe ¹⁶ O ⁺ , ⁵⁹ Co ¹⁶ O ⁺ , ⁶⁰ Ni ¹⁶ O ⁺ , ⁷² Ge ¹⁶ O ⁺ , or ⁷⁷ Se ¹⁶ O ⁺ . ing. As shown in FIG. 6, the MO ⁺ / M ⁺ when O ₃ was supplied to the reaction cell was about 2 to 8 times the MO ⁺ / M ⁺ when O ₂ was supplied to the reaction cell.

From these results, ⁵² Cr ⁺ , ⁵⁵ Mn ⁺ , ⁵⁶ Fe ⁺ , ⁵⁹ Co ⁺ , ⁶⁰ Ni ⁺ , ⁷² Ge ⁺ , or ⁷⁷ Se ⁺ was analyzed by using the mass spectrometer or the mass spectrometry method of the present invention. In this case, each of these element ions can be separated from other element ions having the same mass-to-charge ratio as each of these element ions. That is, by using the mass spectrometer or the mass spectrometry method of the present invention, the analysis sensitivity of ² Cr ⁺ , ⁵⁵ Mn ⁺ , ⁵⁶ Fe ⁺ , ⁵⁹ Co ⁺ , ⁶⁰ Ni ⁺ , ⁷² Ge ⁺ , or ⁷⁷ Se ⁺ is improved. Can be expected.

Claims (7)

A reaction cell into which target ions and interference ions are introduced,
An ozone generator connected to the reaction cell,
A target ion product generated by reacting the target ion with ozone in the reaction cell, according to a mass-to-charge ratio, a mass separation unit separated from the interference ion,
A measurement unit that measures the signal intensity of the target ion product separated by the mass separation unit,
A mass spectrometer having: A reaction cell into which target ions and interference ions are introduced,
An ozone generator connected to the reaction cell,
The mass separation unit, wherein the target ion is separated from an interference ion product generated by reacting the interference ion with ozone in the reaction cell according to a mass-to-charge ratio,
A measurement unit that measures the signal intensity of the target ion separated by the mass separation unit,
A mass spectrometer having: In claim 1 or 2,
A mass spectrometer further comprising another mass separation unit that separates the target ion and the interference ion from various ions according to a mass-to-charge ratio and introduces the ions into the reaction cell. A reaction step of supplying ozone to the target ion and the interference ion to obtain a target ion product that is a reaction product of the target ion and ozone;
Mass separation step of separating the target ion product from the interference ions according to a mass-to-charge ratio,
A measurement step of measuring the signal intensity of the target ion product separated in the mass separation step,
Mass spectrometry method having A reaction step of supplying ozone to the target ion and the interference ion to obtain an interference ion product which is a reaction product of the interference ion and ozone,
Mass separation step of separating the interference ion product from the target ion according to a mass-to-charge ratio,
A measurement step of measuring the signal intensity of the interference ion product separated in the mass separation step,
Mass spectrometry method having In claim 4 or 5,
A mass spectrometric method wherein the target ion is one of Cs ion and Ba ion, and the interference ion is the other of Cs ion and Ba ion. In claim 4 or 5,
A mass spectrometric method wherein the target ion is one of Sr ion and Rb ion, and the interference ion is the other of Sr ion and Rb ion.

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