JP6924511B2 - Mass spectrometry method and mass spectrometer - Google Patents

Description

The present invention relates to a mass spectrometry method, which is a kind of chemical analysis method.

The mass spectrometry method is a method of analyzing based on the ratio of the mass number m of the target ion to be analyzed and the charge z, that is, the mass-to-charge ratio m / z. Non-target ions having a mass-to-charge ratio similar to that of the target ions become interfering ions. In order to analyze the target ion accurately, the interference of the non-target ion must be removed. A high-resolution mass spectrometer can be used to separate the target ions from the interfering ions. However, when the mass-to-charge ratios of the target ion and the interfering ion are slightly different, it is difficult to separate them even by using a high-resolution mass spectrometer.

In the reaction cell technique or the collision cell technique, the target ion or the interfering ion can be separated from the interfering ion by reacting the target ion or the interfering ion with the reaction gas molecule to convert the target ion or the interfering ion into another substance. For example, when the target ion is ³² S ⁺ and the interfering ion is ¹⁶ O ₂ ⁺ , the mass-to-charge ratio is 32 in both cases. Therefore, in the coexistence of ³² S ⁺ and ¹⁶ O ₂ ^{+ , 32} S ⁺ and ¹⁶ O ₂ are reacted to convert ³² S ⁺ to ³² S ¹⁶ O ^+. Then, if the separation mass to charge ratio is 48 and 32 on the basis of ³² S ¹⁶ O ⁺ from ¹⁶ O ₂ ^+, the target ion can be accurately analyzed. The reaction cell technology provides a higher separation effect than a high resolution mass spectrometer. However, in the reaction cell technology, sufficient reactivity may not be obtained by using the 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 an activated reaction gas is reacted with a target ion or an interfering ion to separate the target ion from the interfering ion, so that accurate analysis of the target ion can be performed. It is an object of the present invention to provide a mass spectrometric method and a mass spectrometric apparatus capable of performing the same.

In the mass spectrometer of the present invention, a reaction cell into which a target ion and an interfering ion are introduced, an ozone generator connected to the reaction cell, and a target ion product generated by the reaction of the target ion with ozone in the reaction cell. It has a mass separation unit separated from interfering ions according to the mass-to-charge ratio, and a measurement unit for measuring the signal strength of the target ion product separated by the mass separation unit.

In the other mass spectrometer of the present invention, the reaction cell into which the target ion and the interfering ion are introduced, the ozone generating part connected to the reaction cell, and the target ion are interfering ions in the reaction cell according to the mass-to-charge ratio. It has a mass separator separated from the interfering ion product generated by the reaction of the electric charge with ozone, and a measuring section for measuring the signal strength of the target ion separated by the mass separator.

In the mass spectrometry method of the present invention, ozone is supplied to a target ion and an interfering ion to obtain a target ion product which is a reaction product of the target ion and ozone, and a target ion product is obtained according to a mass-to-charge ratio. It has a mass separation step of separating the ions from the interfering ions and a measurement step of measuring the signal strength of the target ion product separated in the mass separation step.

In another mass spectrometry method of the present invention, ozone is supplied to the target ion and the interfering ion to obtain an interfering ion product which is a reaction product of the interfering ion and the ozone, and interference is obtained according to the mass-to-charge ratio. It has a mass separation step of separating an ion product from a target ion and a measurement step of measuring the signal intensity of the interference ion product separated in the mass separation step.

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

The principle diagram of the mass spectrometer according to the embodiment of this invention. The graph which shows the signal intensity of Ba ion and Ba ion product with respect to mass charge ratio (Example 1). The graph which shows the signal intensity of Cs ion and Cs ion product with respect to mass charge ratio (Example 2). The graph which shows the signal intensity of Sr ion and Sr ion product with respect to mass charge ratio (Example 3). The graph which shows the signal intensity of Rb ion and Rb ion product with respect to mass charge ratio (Example 4). The graph which shows the ratio of the signal strength of MO ^{+ to the signal strength of M + (Example 5).}

FIG. 1 shows the principle of the mass spectrometer according to the embodiment of the present invention. This mass spectrometer includes an ion lens, a QMS1 which is a first mass separator, a reaction cell, an ozone generator which is an ozone generator, a QMS2 which is a second mass separator, and a measurement unit. It has a detector. The ion lens converges various ions and introduces them into QMS1. QMS1 separates target ions and interfering 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 interfering ion separated by QMS1 are introduced into the reaction cell. The ozone generator is connected to the reaction cell, and the taken-in oxygen gas O ₂ is converted into ozone O ₃ and supplied to the reaction cell. The reaction cell, target ions product occurs react purpose ions and O _3. The target ion product may contain elements 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). ) Etc., the target ion product 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 when O ₂ is supplied to the reaction cell and hardly reacts with the target ion, by supplying _{O 3 to the reaction cell, the target ion reacts with O 3} to obtain the target ion product. The ozone generator may take in nitrogen gases 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 interfering ion to change the mass-to-charge ratio of the one ion. Examples of combinations of target ions and interfering ions having the same mass-to-charge ratio include Cs ions and Ba ions, Ba ions and Cs ions, Sr ions and Rb ions, and Rb ions and Sr ions, respectively. In QMS2, the target ion product is separated from the interfering ions according to the mass-to-charge ratio. The detector measures the signal strength 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 the reaction cell of a normal mass spectrometer.

In the present embodiment, the mass-to-charge ratio of interfering ions and comparable objects ions are present in the reaction cell, to obtain the desired ionic product by reacting the desired ion and O ₃ in the reaction cell. Then, the target ion, that is, the target ion product whose mass-to-charge ratio is significantly different from that of the interfering ion is separated from the interfering ion according to the mass-to-charge ratio, and the signal strength of the separated target ion product is measured. By doing so, the target ion is analyzed. Alternatively, the interfering ions in the reaction cell to obtain an interference ion product is reacted with O _3, interfering ions, i.e. from interfering ions product target ions and mass-to-charge ratio is greater different way, the mass to charge The target ions may be separated according to the ratio and the separated target ions may be analyzed.

That is, in the mass spectrometer according to another embodiment of the present invention, the reaction cell into which the target ion and the interfering ion are introduced, the ozone generator which is the ozone generator that supplies ozone to the reaction cell, and the target ion are used. Measurement to measure the signal strength of QMS2, which is a mass separator that separates interfering ions from the interfering ion products generated by the reaction of interfering ions with ozone in the reaction cell, and the target ions separated by QMS2, according to the mass-to-charge ratio. It has a detector with a part.

The mass spectrometric method according to the embodiment of the present invention may or may not use the mass spectrometric apparatus of each embodiment. The mass spectrometric 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 interfering 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 interfering 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 QMS2, and the detector, respectively.

Instead of this method, ozone is supplied to the target ion and the interfering ion to obtain an interfering ion product which is a reaction product of the interfering ion and ozone, and the target ion is extracted from the interfering ion product according to the mass-to-charge ratio. It may be separated and the signal strength of the separated target ion may be measured. The mass spectrometry method of the present embodiment, one mass-to-charge ratios of interfering ions comparable target ions reacted with O _3, since significantly changing the mass-to-charge ratio of the one high precision the desired ions from interfering ions Can be separated by. Therefore, it is possible to analyze the target ion in a state where the target ion is hardly mixed with the interference ion.

Example 1
Inductively coupled plasma tandem quadrupole mass spectrometer as shown in FIG. 1 (ICP-QMS / QMS) ( Agilent, Agilent-8800 type ICP-QMS / QMS system) so as to be supplied to _{O 3} in the reaction cell , Elemental analysis was performed as follows. QMS1 was set so that the ions of m / z = 138 would pass through, and QMS2 was set so that the ions of m / z = 2-260 would pass through. A barium standard solution for mass spectrometry and nitric acid were mixed to prepare a sample solution having a barium content of 1 mg / kg and a nitric acid content of 2% by mass.

This sample solution was charged into the apparatus while supplying the reaction cell with a reaction gas containing _{O 3 or O 2 at 1.0 mL / min.} The reaction gas containing _{O 3} is obtained by supplying _{O 2 to an ozone generator to make the concentration of O 3} 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 the operation and non-operation of the ozone generator, a _{mixed gas of O 3} and O ₂ (hereinafter, may be simply referred to as “O ₃ ” in Examples 1 to 4) or O _{2 in the reaction cell.} Only (hereinafter, may be simply referred to as "O ₂ " in Examples 1 to 4) were supplied.

The signal strength measured by the detection unit is shown in FIG. Note that FIG. 2 shows a value obtained by subtracting the signal intensity of the 2 mass% nitric acid aqueous solution. Further, in FIG. 2, m / z having a high signal strength is selected and shown from m / z = 2 to 260. These are the same in Examples 2 to 4. As shown in FIG. 2, when O ₂ was supplied, a ^{high signal strength of 138} Ba ⁺ (m / z = 138) was observed. On the other hand, when O ₃ was supplied, ^{the signal strength of 138} Ba ⁺ (m / z = 138) was considerably reduced. O ₃ is considered because have high reactivity.

^{As shown below, 138} Ba ⁺ (m / z = 138) introduced into the reaction cell _{reacted with O 3} to produce 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
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 through. The result is shown in FIG. As shown in FIG. 3, a ^{high signal strength 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 strength was extremely low.

From Examples 1 and 2, the Ba ion _{reacts with O 3} to form a Ba ion product and the mass-to-charge ratio changes significantly, whereas the Cs ion _{hardly reacts with O 3} and has a mass charge. The ratio did not change. Therefore, if supplying O ₃ to a reaction cell mass to charge ratio comparable Ba ions and Cs ions are mixed greatly vary the mass to charge ratio of Ba ions according to their mass-to-charge ratio, it can be separated from the Cs ions .. By analyzing the separated Ba ion product, the 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. _{It was also confirmed that even if O 2} was supplied to the reaction cell, Ba ions and Cs ions could not be separated accurately according to the mass-to-charge ratio.

Example 3
Elemental analysis of the sample solution containing the strontium standard solution was performed in the same manner as in Example 1 except that QMS1 was set so that ions of m / z = 88 could pass through. The result is shown in FIG. As shown in FIG. 4, when O ₂ was supplied, a ^{high signal strength of 88} Sr ⁺ (m / z = 88) was observed. On the other hand, when O ₃ was supplied, ^{the signal strength 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
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 pass through. The result is shown in FIG. As shown in FIG. 5, a ^{high signal strength 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 strength was extremely low.

From Examples 3 and 4, the Sr ion _{reacts with O 3} to form an Sr ion product and the mass-to-charge ratio changes significantly, whereas the Rb ion _{hardly reacts with O 3} and has a mass charge. The ratio did not change. Therefore, if supplying O ₃ to a reaction cell mass to charge ratio comparable Sr ions and Rb ions are mixed greatly vary the mass to charge ratio of Sr ions, depending on the mass-to-charge ratio, it can be separated from Rb ions .. By analyzing the separated Sr ion product, the 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 analysis result of the Rb ion containing almost no Sr ion. _{It was also confirmed that even if O 2} was supplied to the reaction cell, Sr ions and Rb ions could not be separated accurately according to the mass-to-charge ratio.

Example 5
Connecting the N ₂ inlet tube into the reaction gas inlet tube 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 tube at a flow rate of 0.7 mL / min. When the ozone generator is operated, a _{mixed gas of O 3} , O ₂ , and N ₂ (hereinafter, may be simply referred to as “O ₃ ” in this embodiment) is introduced into the reaction cell, and the ozone generator is operated. When it was not in operation, _{a mixed gas of O 2} and N ₂ (hereinafter, may be simply referred to as “O ₂ ” in this embodiment) was introduced into 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 ⁺ while supplying _{O 3} or O ₂ to the reaction cell. The liquid was poured into this apparatus, and M ⁺ was introduced into the reaction cells via QMS1 respectively. When either 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 ⁺ that passed through QMS2 were measured by the detectors, respectively.

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 +"} (May be done) is 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, ^{MO +} / M ⁺ _{when O 3} was supplied to the reaction cell was about 2 to 8 times that ^{of 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 ⁺ are analyzed by using the mass spectrometer or mass spectrometry method of the present invention. At the same time, each of these elemental ions can be separated from other elemental ions having a mass-to-charge ratio similar to that of each of these elemental ions. That is, by using the mass spectrometer or 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)

Reaction cells into which target ions and interfering ions are introduced,
The ozone generator connected to the reaction cell and
In the reaction cell, the target ion is generated by reacting with ozone, and the target ion product containing the target ion and oxygen is separated from the interfering ion according to the mass-to-charge ratio.
A measuring unit that measures the signal intensity of the target ion product separated by the mass separating unit, and a measuring unit.
Mass spectrometer with. Reaction cells into which target ions and interfering ions are introduced,
The ozone generator connected to the reaction cell and
A mass separation unit in which the target ion is separated from the interference ion product generated by the reaction of the interference ion with ozone in the reaction cell according to the mass-to-charge ratio.
A measuring unit that measures the signal intensity of the target ion separated by the mass separating unit, and a measuring unit.
Mass spectrometer with. In claim 1 or 2,
Depending on the mass-to-charge ratio, the target ion and the interfering ion, further comprising a mass spectrometer other mass separation unit introduced before Symbol reaction cell separated from a variety of ions. Ozone is supplied to the target ion and interfering ions, Ri reaction products der of the target ions and ozone, the reaction step to obtain the desired ionic product containing the target ion and oxygen,
A mass separation step of separating the target ion product from the interfering ions according to the mass-to-charge ratio,
A measurement step for measuring the signal strength of the target ion product separated in the mass separation step, and a measurement step.
Mass spectrometric method having. A reaction step of supplying ozone to a target ion and an interfering ion to obtain an interfering ion product which is a reaction product of the interfering ion and ozone.
A mass separation step of separating the interference ion product from the target ion according to the mass-to-charge ratio,
A measurement step for measuring the signal strength of the interference ion product separated in the mass separation step, and a measurement step.
Mass spectrometric method having. In claim 4 or 5,
A mass spectrometric method in which the target ion is one of Cs ions and Ba ions, and the interference ion is the other of Cs ions and Ba ions. In claim 4 or 5,
A mass spectrometric method in which the target ions are Sr ions and Rb ions while the interfering ions are Sr ions and Rb ions.

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