JP7704036B2 - Ion Analysis Equipment - Google Patents

Description

The present invention relates to an ion analyzer including a mass analyzer and an ion mobility analyzer, and more specifically to an ion analyzer equipped with an ion source that utilizes the electrospray ionization (ESI) method.

In a liquid chromatograph mass spectrometer (hereinafter referred to as LC-MS), which uses a mass spectrometer as the detector for a liquid chromatograph (LC), an ion source using atmospheric pressure ionization is used, which ionizes compounds in a liquid sample under atmospheric pressure. The most representative atmospheric pressure ionization method is the ESI method. Hereinafter, an ion source using the ESI method will be referred to as an ESI ion source.

As disclosed in Patent Document 1 and the like, the ESI ion source includes a thin, conductive capillary and a cylindrical gas tube arranged concentrically around the capillary so as to surround the periphery of the capillary. When a liquid sample is supplied to the capillary and a high DC voltage is applied to the capillary, an electric field formed near the tip of the capillary imparts an electric charge to the liquid sample. With the help of nebulizing gas blowing out from the gap between the outer periphery of the capillary and the inner periphery of the gas tube, the liquid sample is ejected from the tip of the capillary as charged droplets. The charged droplets come into contact with surrounding gas molecules and are broken down into fine particles, and the solvent in the droplets (including the mobile phase used in liquid chromatography) is vaporized. During this process, the compound molecules contained in the charged droplets become ions and fly out of the droplets. In this way, the ESI ion source can ionize the compounds contained in the liquid sample.

In addition, in order to increase the ionization efficiency, an ESI ion source is also known that sprays a heated inert gas, separate from the nebulizing gas, onto the spray of charged droplets to promote the atomization of the charged droplets and the evaporation of the solvent.

JP 2015-49077 A JP 2012-58122 A US Patent Application Publication No. 2009/0230296 U.S. Pat. No. 8,207,496

In recent years, in LC-MS, there has been a trend to increase the flow rate of the mobile phase supplied to the column in the liquid chromatograph in order to improve analytical throughput. Accordingly, the amount of liquid sample supplied to the ion source of the mass spectrometer also increases. However, conventional general ESI ion sources are not necessarily compatible with such an increase in the amount of liquid delivered, and increasing the amount of liquid delivered can cause problems such as a decrease in ionization efficiency.

As disclosed in Patent Documents 2-4, an ESI ion source capable of handling an increase in the amount of liquid sample delivered is known that has a structure in which multiple capillaries are arranged in a bundle and the liquid sample delivered through a sample supply tube is distributed to the multiple capillaries. With such an ion source, it is possible to reduce the amount of liquid sample delivered to each capillary. However, with such conventional ESI ion sources, although it is certainly possible in principle to improve ionization efficiency by making the charged droplets finer, in practice there is a problem that it is difficult to improve analytical sensitivity.

The present invention was made to solve these problems, and its main objective is to provide an ion analyzer that can ensure high ionization efficiency and improve analytical sensitivity even when the amount of liquid sample delivered is increased.

One aspect of the ion analyzer according to the present invention is an ion analyzer having an ion source utilizing an electrospray ionization method, the ion source comprising:
A plurality of capillaries which spray the supplied liquid sample in the same direction;
one or more auxiliary electrodes arranged so as to be surrounded by the plurality of capillaries;
a voltage application unit that applies a high DC voltage based on the potential of the one or more auxiliary electrodes to the plurality of capillaries;
Equipped with.

Another aspect of the ion analyzer according to the present invention is an ion analyzer having an ion source utilizing an electrospray ionization method, the ion source comprising:
A plurality of capillaries which spray the supplied liquid sample in the same direction;
one or more auxiliary electrodes arranged to surround the plurality of capillaries;
a voltage application unit that applies a high DC voltage based on the potential of the plurality of capillaries to the one or more auxiliary electrodes;
Equipped with.

In the ion analyzer of the above aspect of the present invention, a liquid sample containing the components to be analyzed is distributed to multiple capillaries, and charged droplets are sprayed from each capillary. Therefore, according to the ion analyzer of the above aspect of the present invention, the total amount of liquid sample introduced into the ion source can be increased, thereby improving the throughput of the analysis. Alternatively, the amount of liquid sample flowing through one capillary can be reduced, thereby making it possible to finely atomize the sprayed droplets and promote the generation of ions.

In addition, according to the ion analyzer of the above aspect of the present invention, the electric field strength near the tip of the capillary is enhanced, promoting charge separation of the liquid sample that has reached the tip of the capillary and improving ionization efficiency. At the same time, due to the action of the electric field formed by the auxiliary electrode, the charged droplets sprayed from the capillary and the ions generated from the droplets do not spread, but rather proceed in a converging manner. Therefore, the generated ions can easily enter, for example, a transport tube for transporting the ions into a vacuum chamber, improving the ion collection efficiency. This increases the amount of ions available for analysis, making it possible to achieve high analytical sensitivity.

1 is a diagram showing the overall configuration of a mass spectrometer according to an embodiment of the present invention; 1A is a front plan view of an ESI ion source in a mass spectrometer according to the present embodiment, and FIG. 1B is a cross-sectional view taken along the line A-AA. FIG. 3 is a configuration diagram showing a modified example of the ESI ion source shown in FIG. 2 . FIG. 3 is a configuration diagram showing another modified example of the ESI ion source shown in FIG. 2 . 3A is a front plan view showing still another modified example of the ESI ion source shown in FIG. 2, and FIG. 3B is a cross-sectional view taken along the line A-AA. FIG. 3 is a front plan view showing yet another modified example of the ESI ion source shown in FIG. 2 . 1A is a front plan view of an ESI ion source in a mass spectrometer according to another embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along the line A-AA.

The ion analyzer according to the present invention includes a mass analyzer, an ion mobility analyzer, and an ion mobility-mass analyzer that combines them. The ion source in the ion analyzer according to the present invention is an ESI ion source, and all configurations other than the ion source, such as the mass separation method in the mass analyzer, the presence or absence of an ion dissociation operation, and the dissociation method, can be selected as appropriate.

[First embodiment]
A mass spectrometer, which is an embodiment of an ion analyzer according to the present invention, will be described with reference to the accompanying drawings.
Fig. 1 is an overall configuration diagram of a mass spectrometer according to the present embodiment, and Fig. 2 is a front plan view (A) and a cross-sectional view along the line A-AA (B) showing the configuration of an ESI ion source in the mass spectrometer.
This mass spectrometer is a single-type atmospheric pressure ionization quadrupole mass spectrometer. For convenience of explanation, three mutually orthogonal axes, X, Y, and Z, are defined in space as shown in Figs.

As shown in FIG. 1, in the mass spectrometer of this embodiment, the inside of the chamber 1 is divided into four sections: an ionization chamber 11, a first intermediate vacuum chamber 12, a second intermediate vacuum chamber 13, and an analysis chamber 14. The inside of the ionization chamber 11 is at approximately atmospheric pressure, and the inside of the analysis chamber 14 is maintained at a high vacuum atmosphere by evacuation using a high-performance vacuum pump (usually a combination of a turbomolecular pump and a rotary pump) not shown. The insides of the first intermediate vacuum chamber 12 and the second intermediate vacuum chamber 13 are also evacuated by their own vacuum pumps, and a multi-stage differential pumping system is configured in which the degree of vacuum increases in sequence from the ionization chamber 11 toward the analysis chamber 14.

An ESI probe 2 for ionization is placed in the ionization chamber 11 as an ion source, and the liquid sample containing the sample components is sprayed from the ESI probe 2 as fine charged droplets roughly in the X-axis direction. The charged droplets sprayed from the ESI probe 2 come into contact with the gas in the ionization chamber 11 and are broken down into fine droplets. The droplets also become smaller as the solvent evaporates from the droplets. During this process, the sample components in the droplets acquire an electric charge and fly out, becoming ions.

The ionization chamber 11 and the first intermediate vacuum chamber 12 are connected through a thin-diameter desolvation tube 3. The central axis of the ion intake port 3a, which is the opening of the desolvation tube 3 on the ionization chamber 11 side, extends approximately parallel to the Z axis. In other words, the direction of spray from the ESI probe 2 and the central axis of the ion intake port 3a (i.e., the direction of ion intake) are approximately perpendicular. Since there is a pressure difference between the two open ends of the desolvation tube 3, this pressure difference forms a gas flow that flows from the ionization chamber 11 to the first intermediate vacuum chamber 12 through the desolvation tube 3. Ions derived from the sample components generated in the ionization chamber 11 are mainly sucked into the desolvation tube 3 through the ion intake port 3a on this gas flow and are expelled into the first intermediate vacuum chamber 12 together with the gas flow.

A multipole ion guide 4 is placed inside the first intermediate vacuum chamber 12, and a skimmer 5 with a small hole at the top is provided on the partition separating the first intermediate vacuum chamber 12 and the second intermediate vacuum chamber 13. Ions are focused near the small hole of the skimmer 5 by the action of the electric field formed by the ion guide 4, and are sent through the small hole to the second intermediate vacuum chamber 13.

A multipole ion guide 6 is also arranged inside the second intermediate vacuum chamber 13, and ions are focused by the action of the electric field formed by the ion guide 6 and sent to the analysis chamber 14. A quadrupole mass filter 7 and an ion detector 8 are arranged inside the analysis chamber 14. Ions are introduced into the space in the longitudinal direction of the quadrupole mass filter 7 along the ion optical axis C, and only ions having a specific mass-to-charge ratio pass through the quadrupole mass filter 7 and reach the ion detector 8 due to the action of the electric field formed by the voltage applied to the quadrupole mass filter 7. The ion detector 8 generates a detection signal according to the amount of ions that have reached it and sends it to a data processing unit (not shown). In this mass spectrometer, the analytical sensitivity can be improved by sending a larger amount of ions to the quadrupole mass filter 7, that is, by subjecting them to analysis.

Next, the configuration of the ESI probe 2 will be described in detail with reference to FIG.
Fig. 2(A) is a diagram showing the ESI probe 2 as seen from the front in the direction of travel of the spray of charged droplets, and Fig. 2(B) is a cross-sectional view taken along the line A-AA in Fig. 2(A).

As shown in FIG. 2(A), the ESI probe 2 includes eight conductive capillaries 211-218 arranged at approximately equal angular intervals (45° angular intervals in this example) on the same circumference U and extending in a direction parallel to the axis S of the circle, and cylindrical nebulizing gas tubes 221-228 having a double-tube structure concentric with each of the eight capillaries 211-218 for each of the eight capillaries 211-218. The ESI probe 2 also includes a cylindrical auxiliary electrode 23 extending in a direction parallel to the axis S at the position of the axis S, which is the center of the circle on which the eight capillaries 211-218 are arranged. The tip of the auxiliary electrode 23 protrudes in the X-axis direction beyond the tips of the capillaries 211-218.

That is, in the ESI probe 2, one auxiliary electrode 23 is arranged so as to be surrounded by eight capillaries 211 to 218. The distance between the auxiliary electrode 23 and each of the eight capillaries 211 to 218 is approximately the same. The configuration of one capillary and the nebulizing gas tube having a double cylindrical structure therewith is equivalent to the configuration of the capillary and nebulizing gas tube in a conventional general ESI probe.

The auxiliary electrode 23 is grounded and the potential is fixed at zero. A high DC voltage of, for example, several kV or more is applied to each capillary 211-218 from a high DC voltage power supply 24. The polarity of this voltage is the same as the polarity of the ions to be measured. When the ions to be measured are positive ions, a positive DC high voltage Vh is applied to the capillaries 211-218 (however, to avoid cluttering the drawing, only the voltage application line connected to one capillary 214 is drawn in FIG. 2(A)).

The following describes the ion generation operation in the ESI probe 2. Here, it is assumed that the measurement target is positive ions, as an example.
Although not shown, for example, when a liquid sample containing compounds separated in a column of a liquid chromatograph is supplied to the ESI probe 2, the liquid sample is distributed in approximately equal amounts to the eight capillaries 211 to 218 and reaches the tips of the capillaries 211 to 218. Meanwhile, an appropriate inert gas is supplied to the nebulizing gas tubes 221 to 228 as a nebulizing gas.

When a positive high voltage is applied to the capillaries 211-218, a strong electric field is formed near the tip of each capillary 211-218 due to the potential difference between the auxiliary electrode 23, which has a zero potential, and each capillary 211-218. In a typical ESI ion source, the reference potential for the capillary potential (usually the ground potential) is the potential near the inlet end of the desolvation tube 3 in FIG. 1. In contrast, in the mass spectrometer of this embodiment, the auxiliary electrode 23, which is the reference ground potential, is disposed close to the capillaries 211-218. Therefore, the electric field formed near the tip of each capillary 211-218 is strong, and the Coulomb repulsion acting on the charged droplets formed at the tip of each capillary 211-218 is large. As a result, the charged droplets are easily atomized, and with the help of the nebulizing gas, a large amount of fine charged droplets are sprayed from each capillary 211-218.

By using multiple capillaries and placing an auxiliary electrode at a reference potential close to the capillaries, a large amount of fine charged droplets are sprayed, but because these charged droplets are charged with the same polarity, Coulomb repulsion acts between them. Therefore, if there is no influence of an external electric field, the spray flow of charged droplets will spread in a direction perpendicular to its axis as it progresses, making it difficult to efficiently suck the ions generated from the charged droplets into the desolvation tube 3.

In contrast, in the mass spectrometer of this embodiment, the potential of the auxiliary electrode 23 arranged on the axis S is lower than the potential of the capillaries 211 to 218 around it, so that a potential gradient is formed from the surroundings toward the axis S in the plane (Y-Z plane) perpendicular to the axis S. That is, a converging electric field is formed in front of the tips of the capillaries 211 to 218 to converge positively charged particles (charged droplets, ions) near the axis S. The charged droplets sprayed from the capillaries 211 to 218 and the ions generated from the charged droplets are subjected to a force by this converging electric field in a direction approaching the axis S, as shown by the thick arrow in FIG. 2B. Therefore, the spray flow containing the charged droplets and ions is prevented from spreading due to Coulomb repulsion, and the ions generated therefrom are efficiently sucked into the desolvation tube 3.

As described above, in the mass spectrometer of this embodiment, the auxiliary electrode 23 has the effect of increasing the electric field strength near the tips of the capillaries 211-218 and the effect of converging the spray flow containing charged droplets and ions near the axis S. As a result, in this ESI probe 2, the ionization efficiency can be increased to generate a larger amount of ions, and the ion collection efficiency can be increased to more efficiently capture the generated ions into the desolvation tube 3 and send them to the subsequent stage.

[First Modification of the First Embodiment]
3 and 4 are diagrams showing a modified example of the ESI probe 2 in the mass spectrometer of the above embodiment. Note that although only a portion of the capillaries 211 to 218 and the nebulizing gas tubes 221 to 228 are shown, their configurations are the same as those shown in FIG.

The ESI probe 2A shown in FIG. 3 includes a donut-shaped heated gas supply unit 25 arranged to surround multiple capillaries 211-218. This heated gas supply unit 25 has heated gas outlets 251 that are continuous around the entire circumference of the axis S or that are provided at predetermined angular intervals around the axis S. These heated gas outlets 251 are provided at an inward angle so that the ejected gas is directed toward the axis S. Therefore, the heated gas ejected from the heated gas outlets 251 surrounds the spray of charged droplets and hits its outer periphery.

In the ESI probe 2A, due to the action of both the converging electric field formed by the auxiliary electrode 23 described above and the nebulizing gas flow ejected from each of the nebulizing gas tubes 221-228, the smaller the mobility of the charged droplets, i.e., the larger the size of the droplets, the more likely they are to be located on the outer periphery of the spray flow P. As Coulomb repulsion is less likely to act on the interior of large charged droplets, they are less likely to be miniaturized and the ionization efficiency is less likely to increase.

In contrast, the heated gas ejected from the heated gas ejection port 251 efficiently strikes the large charged droplets located on the outer periphery of the spray flow P. This promotes the evaporation of the solvent in such charged droplets, and promotes the fragmentation of the droplets and the generation of ions. This allows the ESI probe 2A according to this modified example to further increase the ionization efficiency.

On the other hand, the ESI probe 2B shown in FIG. 4 includes a heated gas supply unit 26 that ejects heated gas across the spray flow P of charged droplets from the multiple capillaries 211-218. Even with this configuration, the heated gas can efficiently impinge on the large charged droplets located on the outer periphery of the spray flow P, promoting the evaporation of the solvent from the charged droplets.

[Second Modification of the First Embodiment]
In the ESI probes 2, 2A, and 2B in the mass spectrometer of the above embodiment, the multiple capillaries 211 to 218 are arranged at approximately the same angular intervals on approximately the same circumference U. As a result, a roughly uniform amount of charged droplets is sprayed in the circumferential direction around the auxiliary electrode 23. However, the amount of ions generated from the thus sprayed charged droplets and drawn into the desolvation tube 3 is unlikely to be uniform in the circumferential direction around the auxiliary electrode 23. One of the reasons for this is that the desolvation tube 3 and the partition wall separating the ionization chamber 11 from the first intermediate vacuum chamber 12 are at ground potential or a potential close to it (at least a potential much closer to ground potential than the potentials of the capillaries 211 to 218), so that the efficiency of ion generation is relatively low in the spray flow from the capillaries located close to the desolvation tube 3 or the partition wall. The second reason is that although there is a focusing effect due to the electric field from the auxiliary electrode 23, the charged droplets sprayed from the ESI probe 2 and the ions generated from them are not focused into a beam, so the ions generated from the spray flow from the capillary located close to the desolvation tube 3 (the capillary located in the positive direction of the Z axis in Figure 1) are relatively less likely to be sucked into the desolvation tube 3.

There is also the problem that the charged droplets sprayed from the capillary located close to the desolvation tube 3 and the ions generated from them tend to adhere to the ion intake port 3a of the desolvation tube 3 and the outer surface of the tube, causing contamination. A modified example of the mass spectrometer of the above embodiment shown in Figure 5 can address this problem. Figure 5 shows a front plan view (A) and a cross-sectional view along the line A-AA (B) of the ESI probe 2C of this modified example. Figure 5 also partially illustrates the desolvation tube 3, which is not shown in Figure 2. In the figure, the same components as those shown in Figure 2 are given the same reference numerals, and explanations are omitted unless otherwise required.

In this ESI probe 2C, the eight capillaries 211-218 are arranged on the same circumference U, and in the range from capillary 211 to capillary 218 in the clockwise direction in FIG. 5(A), the angular interval between two adjacent capillaries in the circumferential direction is the same. On the other hand, the angular interval between capillary 218 and the adjacent capillary 211 is wider than the others. Specifically, the former is 40°, and the latter is twice as wide, at 80°. The eight capillaries 211-218 of the ESI probe 2C can also be considered as a state in which one capillary has been removed from a state in which nine capillaries, including the eight capillaries, are arranged on the same circumference U at equal angular intervals. The removed capillary is a capillary that is located at a position where the desolvation tube 3 is located on the extension line of the central axis of that capillary.

Therefore, when looking at the positional relationship between the desolvation tube 3 and the multiple capillaries 211-218 in the Y-Z plane as shown in Figure 5 (A), the conduit of the desolvation tube 3 is located at a position where the multiple capillaries 211-218 are not present, that is, at a point where the distance between two circumferentially adjacent capillaries on the circumference U is wide. In addition, a conductive electrode holding part 28 that is substantially integrated with the auxiliary electrode 23 is arranged at a position overlapping the desolvation tube 3 in the Y-Z plane and spaced apart in the negative direction of the X axis to hold the auxiliary electrode 23 and apply a ground potential to the auxiliary electrode 23.

A strong electric field is formed near the tip of each capillary 211-218 by applying a high DC voltage Vh to each capillary 211-218. The liquid sample distributed to each capillary 211-218 is charged by this electric field and sprayed as fine charged droplets with the help of nebulizing gas. This is similar to the mass spectrometer of the above embodiment. In this modified mass spectrometer, each capillary 211-218 is relatively far from the desolvation tube 3, and the electric field formed near the tip of each capillary 211-218 is less susceptible to the potential of the desolvation tube 3 or the partition. Therefore, charged droplets are generated well in each capillary 211-218, and ionization is performed efficiently. In addition, since there is no desolvation tube 3 in front of the spray flow generated by any of the capillaries 211 to 218, the fine charged droplets in the spray flow and the ions generated from the spray flow are easily drawn into the desolvation tube 3 without adhering to the ion intake port 3a or the pipe line of the desolvation tube 3. This also improves the efficiency of ion collection.

This allows a larger amount of ions to be sent to the subsequent stage, achieving high analytical sensitivity. It also reduces contamination caused by charged droplets and ions adhering to the ion intake port 3a of the desolvation tube 3 and the piping. This allows the performance of the device to be maintained for a long period of time, and the burden of maintenance work for the device to be reduced. Furthermore, by positioning the electrode holder 28 that holds the auxiliary electrode 23 in a space that ensures a wide gap between adjacent capillaries, it is possible to stably hold the auxiliary electrode 23 while reliably ensuring electrical insulation between the electrode holder 28 and each of the capillaries 211-218 and the nebulizing gas tubes 221-228.

It is apparent that this modified example may also be configured to add the heating gas supply units 25 and 26 as shown in FIGS.
In addition, it is not essential that the intervals between adjacent capillaries are equiangular as described above except where a wide space is provided. In addition, the central axis of the ion intake port 3a of the desolvation tube 3 and the axis S of the ESI probe 2C may be obliquely intersecting each other instead of being perpendicular to each other.

[Other variations]
Furthermore, the configurations of the ESI probes 2, 2A, 2B, and 2C in the above-described embodiment and modified examples can be modified in various ways.
For example, the number of capillaries is not limited to the above, and can be determined as appropriate as long as there are multiple capillaries. In addition, it is not essential that the multiple capillaries 211 to 218 are arranged on the same circumference U, and they can be arranged as appropriate. However, if the distance between each capillary and the auxiliary electrode 23 is different, the strength of the electric field formed near the tip of the capillary will vary, and the size of the charged droplets sprayed from the capillary will also vary greatly. Therefore, in order to make the size of the charged droplets as uniform as possible and increase the ionization efficiency, it is better that the distance between each of the multiple capillaries 211 to 218 and the auxiliary electrode 23 is as equal or close as possible.

The shape of the auxiliary electrode 23 is not limited to the cylindrical shape described above. In particular, the shape of the tip of the auxiliary electrode 23 is not limited to a planar shape parallel to the Y-Z plane, but may be a hemispherical or other appropriate shape, thereby adjusting the potential gradient of the converging electric field and improving the convergence of the spray flow.

Furthermore, the number of auxiliary electrodes 23 is not limited to one, and a plurality of auxiliary electrodes may be provided.
6 is a diagram showing a modified example in which auxiliary electrodes 231-238 are provided corresponding to the eight capillaries 211-218, respectively. This diagram is a front plan view of the ESI probe 2 as seen from the same viewpoint as in FIG. 2(A). Even with this configuration, a strong DC electric field can be formed near the tip of each of the capillaries 211-218, and an electric field can be formed that converges the spray of charged droplets ejected from each of the capillaries 211-218 near the axis S.

[Second embodiment]
Next, a mass spectrometer which is another embodiment of the ion analyzer according to the present invention will be described. The overall configuration of this mass spectrometer is the same as that of the first embodiment, and therefore the description will be omitted. Fig. 7 is a front plan view (A) and a cross-sectional view along the line A-AA (B) showing the configuration of the ESI ion source in the mass spectrometer of this embodiment. In Fig. 7, components which are substantially the same as those of the ESI ion source in the mass spectrometer of the first embodiment are given the same reference numerals, and descriptions will be omitted unless otherwise required.

In the ESI probe 2E of this ESI ion source, the configuration and arrangement of the capillaries 211-218 and nebulizing gas tubes 221-228 are the same as in the first embodiment, but the shape and arrangement of the auxiliary electrodes and the applied voltage are different from those in the first embodiment.
That is, the auxiliary electrode 27 is a substantially cylindrical conductor arranged to surround the capillaries 211 to 218. The axis of this auxiliary electrode 27 coincides with the axis S of the circle on which the eight capillaries 211 to 218 are arranged. Therefore, even in this embodiment, the distance between the auxiliary electrode 27 and each of the capillaries 211 to 218 is substantially the same.

All eight capillaries 211 to 218 are grounded (however, to avoid cluttering the drawing, FIG. 7(A) only shows the ground wire connected to one capillary 215). On the other hand, a high DC voltage of, for example, several kV or more is applied to the auxiliary electrode 27 from a high DC voltage power supply 24. The polarity of this voltage is the same as the polarity of the ions to be measured, and if the ions to be measured are positive ions, the high DC voltage is positive.

When a liquid sample is introduced into each of the capillaries 211-218 and a positive high-polarity DC voltage is applied to the auxiliary electrode 27, a strong electric field is formed near the tip of each of the capillaries 211-218 because the capillaries 211-218 and the auxiliary electrode 27 are in close proximity. This makes it easy for the charged droplets formed at the tip of each of the capillaries 211-218 to be atomized, and with the help of the nebulizing gas, a large amount of fine charged droplets are sprayed from each of the capillaries 211-218.

These charged droplets have a positive charge, but because a positive high voltage is applied to the auxiliary electrode 27 surrounding the eight capillaries 211-218, an electric field is formed that exerts a force that pushes the positively charged droplets (and the positive ions that fly out of the droplets) toward the inner circumference, that is, toward the axis S. As a result, as in the first embodiment, although there is Coulomb repulsion between the charged droplets, the spray flow of the charged droplets is less likely to spread and converges near the axis S. As a result, the ions efficiently generated from the charged droplets are efficiently sucked into the desolvation tube 3 and transported to the subsequent stage.

In the second embodiment as well, various modifications can be made in the same manner as in the first embodiment.
That is, similar to the configurations shown in Figures 3 and 4, a donut-shaped heated gas supply unit 25 may be added to the outer periphery of the auxiliary electrode 27, or a heated gas supply unit 26 may be added that sprays heated gas so as to cross the spray flow P of charged droplets from the multiple capillaries 211 to 218.
In addition, the number and arrangement of the capillaries may be changed as appropriate. The shape of the auxiliary electrode 27 is not limited to a cylindrical shape, and the auxiliary electrode 27 may be divided into a plurality of parts as appropriate.

Furthermore, the above first and second embodiments and their modifications are merely examples of the present invention, and it goes without saying that appropriate changes, modifications, and additions made within the spirit of the present invention are also encompassed within the scope of the claims of this application.

For example, the above embodiment is a single-type quadrupole mass spectrometer, but as described above, the mass separation method, the presence or absence of ion dissociation operation and the dissociation method can be selected appropriately, so it goes without saying that the present invention can be applied to various mass spectrometers such as time-of-flight mass spectrometers, ion trap mass spectrometers, triple quadrupole mass spectrometers, quadrupole-time-of-flight mass spectrometers, and ion trap time-of-flight mass spectrometers.

In addition, the present invention is applicable to all devices that ionize and analyze sample components using an ESI ion source, and is not limited to mass spectrometers, but may also be an ion mobility spectrometer or an ion mobility-mass spectrometer that combines an ion mobility spectrometer and a mass spectrometer.

[Various aspects]
It will be appreciated by those skilled in the art that the exemplary embodiments described above are examples of the following aspects.

(Item 1) One aspect of the ion analyzer according to the present invention is an ion analyzer having an ion source utilizing an ESI method, the ion source comprising:
A plurality of capillaries which spray the supplied liquid sample in the same direction;
one or more auxiliary electrodes arranged so as to be surrounded by the plurality of capillaries;
a voltage application unit that applies a high DC voltage based on the potential of the one or more auxiliary electrodes to the plurality of capillaries;
Equipped with.

(Item 10) Another aspect of the ion analyzer according to the present invention is an ion analyzer having an ion source utilizing an ESI method, the ion source comprising:
A plurality of capillaries which spray the supplied liquid sample in the same direction;
one or more auxiliary electrodes arranged to surround the plurality of capillaries;
a voltage application unit that applies a high DC voltage based on the potential of the plurality of capillaries to the one or more auxiliary electrodes;
Equipped with.

In the ion analyzer described in paragraphs 1 and 10, a liquid sample containing the components to be analyzed is distributed to multiple capillaries, and charged droplets are sprayed from each capillary. This allows the total amount of liquid sample introduced into the ion source to be increased, improving the throughput of analysis. Alternatively, the amount of liquid sample flowing through one capillary can be reduced, thereby making it possible to finely atomize the sprayed droplets and promote the generation of ions.

In the ion analyzer described in paragraphs 1 and 10, the auxiliary electrode is placed close to the capillary, and the electric field strength near the tip of the capillary is enhanced. This promotes charge separation of the liquid sample that has reached the tip of the capillary, improving ionization efficiency. At the same time, due to the action of the electric field formed by the auxiliary electrode, the charged droplets sprayed from the capillary and the ions generated from the droplets do not spread, but rather proceed in a convergent manner. This makes it easier for the generated ions to enter a transport tube for transporting the ions, for example, into a vacuum chamber, improving ion collection efficiency. This increases the amount of ions to be analyzed, making it possible to achieve high analytical sensitivity.

(Paragraph 2, Paragraph 11) In the ion analyzer described in paragraph 1 or paragraph 10, the ion source may further include a nebulizing gas tube provided individually for each of the capillaries, which ejects a nebulizing gas in the same direction as the liquid sample is sprayed from the capillary.

The ion analyzer described in paragraphs 2 and 11 allows for good spraying of charged droplets from the tip of the capillary.

(3) In the ion analyzer according to the first or second aspect,
The plurality of capillaries are arranged on approximately the same circumference,
The auxiliary electrode may be one, and may be disposed approximately at the center of the circle on which the capillaries are disposed.

(12) Similarly, in the ion analyzer according to the 10th or 11th aspect,
The plurality of capillaries are arranged on approximately the same circumference,
The auxiliary electrode may be one and may have a cylindrical shape coaxial with the circle on which the plurality of capillaries are arranged.

In the ion analyzer described in paragraphs 3 and 12, the electric field strength near the tip of each capillary is approximately the same, so that each capillary can spray charged droplets that have been made fine to the same extent. This can improve the ionization efficiency. In addition, in the ion analyzer described in paragraphs 3 and 12, the potential gradient of the electric field in the region where the spray flow of charged droplets is formed is approximately rotationally symmetrical around the axis of the spray flow due to the potential of each capillary and the potential of the auxiliary electrode. This makes it easier for the spray flow of charged droplets to converge near the axis, improving the efficiency of use of ions generated from the charged droplets. This allows a larger amount of ions to be used for analysis, further improving the analytical sensitivity.

(4) The ion analyzer described in (3) collects ions generated from the spray stream from the plurality of capillaries and transports them to a subsequent stage, and is provided with an ion transport tube having an ion intake port in front of the spray stream and including a pipe extending in a direction intersecting the direction of spray from the capillaries;
The plurality of capillaries may be arranged on approximately the same circumference, except for a position where the ion transport tube is present on an extension of the direction of spray.

(5) In the ion analyzer described in 4, the ion transport pipe may extend in a direction substantially perpendicular to the direction of spray from the capillary.

In general, the ion transport tube is set to ground potential or a potential relatively close to it, and as a result, the electric field formed at the tip of the capillary located near the ion transport tube is easily weakened. In addition, the charged droplets sprayed from the capillary located near the ion transport tube and the ions generated by them are less likely to ride the gas flow flowing into the ion transport tube and are less likely to be taken into the ion transport tube. In contrast, according to the ion analysis device described in paragraphs 4 and 5, since all of the multiple capillaries are positioned relatively far from the ion transport tube, a strong electric field is formed near the capillary tip, and charged droplets are generated well. In addition, fine charged droplets contained in the spray flow and ions generated from them are efficiently taken into the ion transport tube. This allows more ions to be sent to the subsequent stage, and the analytical sensitivity can be increased. In addition, it is possible to reduce contamination caused by charged droplets and ions adhering to the ion transport tube and its ion intake port.

(6) In the ion analyzer according to the 4th or 5th aspect, the plurality of capillaries are arranged such that the interval between adjacent capillaries on the circumference in the circumferential direction is widest at a position where the ion transport tube is located on an extension of the spray direction,
A holder for holding the auxiliary electrode and/or wiring for applying a potential to the auxiliary electrode may be disposed in the widest space between the adjacent capillaries.

According to the ion analyzer described in paragraph 6, the auxiliary electrode holder and wiring can be arranged in a sufficiently large space between adjacent capillaries, and electrical insulation between the holder or wiring and the capillaries can be sufficiently ensured.

(Items 7 and 13) The ion analyzer described in any one of items 1 to 6 or any one of items 10 to 12 may further include a heated gas supply unit that sprays heated gas onto the outside of the spray stream from the multiple capillaries so as to surround it.

In the ion analysis device described in paragraphs 7 and 13, the heated gas ejected from the heated gas supply unit mainly hits the outer peripheral portion of the spray of charged droplets ejected from the multiple capillaries. This portion contains relatively large charged droplets, and this promotes the evaporation of the solvent in the charged droplets, which is effective in increasing the ionization efficiency. In addition, since a heated gas flow is formed to surround the spray of charged droplets, the spread of the spray can be further suppressed, and the efficiency of ion utilization is further improved.

(Items 8 and 14) The ion analyzer described in any one of items 1 to 6 or any one of items 10 to 12 may further include a heating gas supply unit that sprays a heating gas onto the spray stream from the multiple capillaries so as to intersect with the spray stream.

In the ion analyzer described in paragraphs 8 and 14, the heated gas ejected from the heated gas supply unit mainly hits the outer peripheral portion of the spray of charged droplets ejected from the multiple capillaries. This portion contains relatively large charged droplets, and this promotes the evaporation of the solvent in the charged droplets, which is effective in increasing the ionization efficiency.

(Items 9 and 15) The ion analyzer described in any one of items 1 to 8 or any one of items 10 to 14 may be a single-type quadrupole mass analyzer, a triple quadrupole mass analyzer, or a quadrupole time-of-flight mass analyzer having the ion source.

In such a mass spectrometer, it is necessary to transport ions from the ion source in an atmospheric pressure environment to a downstream vacuum chamber through a desolvation tube, sampling cone, etc., but the mass spectrometer described in paragraphs 9 and 15 can efficiently collect ions generated in the ion source and transport them to the downstream stage. As a result, the mass spectrometer described in paragraphs 9 and 15 can achieve high analytical sensitivity.

1...Chamber 11...Ionization chamber 12...First intermediate vacuum chamber 13...Second intermediate vacuum chamber 14...Analysis chamber 2, 2A, 2B, 2C, 2D, 2E...ESI probe 211-218...Capillary 221-228...Nebulizing gas tube 23, 231-238, 27...Auxiliary electrode 24...DC high voltage power supply 25, 26...Heated gas supply unit 251...Heated gas outlet 28...Electrode holder 3...Desolvation tube 4, 6...Ion guide 5...Skimmer 7...Quadrupole mass filter 8...Ion detector

Claims (15)

An ion analysis apparatus having an ion source utilizing an electrospray ionization method, the ion source comprising:
A plurality of capillaries which spray the supplied liquid sample in the same direction;
one or more auxiliary electrodes arranged so as to be surrounded by the plurality of capillaries;
a voltage application unit that applies a high DC voltage based on the potential of the one or more auxiliary electrodes to the plurality of capillaries;
An ion analyzer comprising: The ion analyzer according to claim 1, further comprising a nebulizing gas tube provided individually for each of the capillaries, which ejects a nebulizing gas in the same direction as the liquid sample is sprayed from the capillary. The plurality of capillaries are arranged on approximately the same circumference,
3. The ion analyzer according to claim 1, wherein the auxiliary electrode is one and is disposed at approximately the center of the circle on which the plurality of capillaries are disposed. an ion transport tube that collects ions generated from the spray stream from the plurality of capillaries and transports them to a subsequent stage, the ion transport tube having an ion intake port in front of the spray stream and including a pipe extending in a direction intersecting the direction of spray from the capillaries;
4. The ion analyzer according to claim 3, wherein the plurality of capillaries are arranged on approximately the same circumference, except for a position where the ion transport tube is present on an extension of the direction of spray. The ion analyzer according to claim 4, wherein the ion transport pipe extends in a direction substantially perpendicular to the direction of spray from the capillary. the plurality of capillaries are arranged such that the interval between adjacent capillaries on the circumference in the circumferential direction is widest at a position where the ion transport tube is located on an extension of the spray direction;
6. The ion analyzer according to claim 4, wherein a holder for holding the auxiliary electrode and/or wiring for applying a potential to the auxiliary electrode are disposed in the widest space between the adjacent capillaries. The ion analyzer according to any one of claims 1 to 6, further comprising a heating gas supply unit that sprays a heating gas onto the outside of the spray stream from the multiple capillaries so as to surround it. The ion analyzer according to any one of claims 1 to 6, further comprising a heating gas supply unit that sprays a heating gas onto the spray stream from the multiple capillaries so as to intersect with the spray stream. The ion analyzer according to any one of claims 1 to 8, which is a single-type quadrupole mass analyzer, a triple quadrupole mass analyzer, or a quadrupole-time-of-flight mass analyzer having the ion source. An ion analysis apparatus having an ion source utilizing an electrospray ionization method, the ion source comprising:
A plurality of capillaries which spray the supplied liquid sample in the same direction;
one or more auxiliary electrodes arranged to surround the plurality of capillaries;
a voltage application unit that applies a high DC voltage based on the potential of the plurality of capillaries to the one or more auxiliary electrodes;
An ion analyzer comprising: The ion analyzer according to claim 10, further comprising a nebulizing gas tube provided individually for each of the capillaries, which ejects a nebulizing gas in the same direction as the liquid sample is sprayed from the capillary. The plurality of capillaries are arranged on approximately the same circumference,
12. The ion analyzer according to claim 10, wherein the auxiliary electrode is a single electrode having a cylindrical shape coaxial with a circle on which the plurality of capillaries are arranged. The ion analyzer according to any one of claims 10 to 12, further comprising a heating gas supply unit that sprays a heating gas onto the outside of the spray stream from the multiple capillaries so as to surround it. The ion analyzer according to any one of claims 10 to 12, further comprising a heating gas supply unit that sprays a heating gas onto the spray stream from the multiple capillaries so as to intersect with the spray stream. The ion analyzer according to any one of claims 10 to 14, which is a single-type quadrupole mass analyzer, a triple quadrupole mass analyzer, or a quadrupole-time-of-flight mass analyzer having the ion source.

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