Ion analyzer

Abstract

To improve the ionization efficiency and ion collection efficiency in an ESI ion source to improve analytical sensitivity while increasing analytical throughput.SOLUTION: An ion analyzer according to the present invention includes an ion source using an ESI method, and the ion source (2) includes a plurality of capillaries (211 to 218) that sprays a supplied liquid sample in the same direction, one or more auxiliary electrodes (23, 231 to 238) arranged to be surrounded by the plurality of capillaries, and a voltage applying unit (24) that applies a DC high voltage based on the potential of one or more auxiliary electrodes to the plurality of capillaries.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an ion analyzer including a mass spectrometer and an ion mobility analyzer, and more particularly to an ion analyzer provided with an ion source using an electrospray ionization (ESI) method.

Background Art

[0002] In a liquid chromatography-mass spectrometry (hereinafter referred to as LC-MS) using a mass spectrometer as a detector of a liquid chromatograph (LC), an ion source based on an atmospheric pressure ionization method for ionizing a compound in a liquid sample under atmospheric pressure is used. Among the atmospheric pressure ionization methods, the most representative one is the ESI method. Hereinafter, an ion source using the ESI method is referred to as an ESI ion source.

[0003] As disclosed in Patent Document 1 and the like, an ESI ion source includes a capillary having a small diameter and being conductive, and a cylindrical gas tube arranged concentrically with the capillary so as to surround the periphery of the capillary. When a liquid sample is supplied to the capillary and a DC high 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 a nebulizing gas blown out from the gap between the outer periphery of the capillary and the inner periphery of the gas tube, the liquid sample ejects from the tip of the capillary as a charged droplet. This charged droplet is refined by contacting surrounding gas molecules, and the solvent (including the mobile phase used in the liquid chromatograph) in the droplet vaporizes. In the process, the compound molecules contained in the charged droplet become ions and jump out of the droplet. In this way, the ESI ion source can ionize the compounds contained in the liquid sample.

[0004] In addition, in order to improve the ionization efficiency, an ESI ion source is also known which, separately from the nebulizing gas, blows a heated inert gas onto the spray stream of the charged droplet to promote the refinement of the charged droplet and the vaporization of the solvent.

Prior Art Documents

Patent Document

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0006] In recent years, in LC-MS, in order to improve the analysis throughput, there has been a tendency to increase the liquid feeding flow rate of the mobile phase supplied to the column in the liquid chromatograph. Along with this, the liquid feeding amount of the liquid sample supplied to the ion source of the mass spectrometer also increases. However, conventional general ESI ion sources do not necessarily cope with such an increase in the liquid feeding amount, and problems such as a decrease in ionization efficiency may occur when the liquid feeding amount is increased.

[0007] As an ESI ion source capable of coping with an increase in the liquid feeding amount of a liquid sample, as disclosed in Patent Documents 2-4, there is known a structure in which a plurality of capillaries are provided in a bundle shape, and the liquid sample supplied through the sample supply pipe is distributed to the plurality of capillaries. In such an ion source, the amount of the liquid sample supplied to one capillary can be reduced. However, in such a conventional ESI ion source, although in principle it is possible to improve the ionization efficiency by miniaturizing the charged droplets, in practice, there is a problem that it is difficult to lead to an improvement in the analysis sensitivity.

[0008] The present invention has been made to solve such problems, and its main object is to provide an ion analyzer capable of ensuring high ionization efficiency and improving the analysis sensitivity even when the liquid feeding amount of the liquid sample is increased.

Means for Solving the Problem

[0009] One aspect of the ion analyzer according to the present invention is an ion analyzer including an ion source using an electrospray ionization method, wherein the ion source includes a plurality of capillaries for spraying a 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 DC high voltage based on the potential of the one or more auxiliary electrodes to the plurality of capillaries, and is provided with.

[0010] Another aspect of the ion analyzer according to the present invention is an ion analyzer including an ion source using an electrospray ionization method, wherein the ion source includes a plurality of capillaries for spraying a supplied liquid sample in the same direction, one or more auxiliary electrodes arranged so as to surround the plurality of capillaries, a voltage application unit that applies a DC high voltage based on the potential of the plurality of capillaries to the one or more auxiliary electrodes, and is provided with.

Advantages of the Invention

[0011] In the ion analyzer of the above aspect of the present invention, a liquid sample containing a component to be analyzed is distributed to a plurality of capillaries, and charged droplets are sprayed from each capillary. Therefore, according to the ion analyzer of the above aspect of the present invention, the amount of the entire liquid sample introduced into the ion source can be increased, thereby improving the analysis throughput. Alternatively, the amount of the liquid sample flowing through one capillary can be reduced, thereby miniaturizing the sprayed droplets and promoting the generation of ions.

[0012] Further, according to the ion analyzer of the above aspect of the present invention, since the electric field strength near the tip of the capillary is enhanced, charge separation of the liquid sample reaching the tip of the capillary is promoted, and the ionization efficiency is improved. 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 instead converge and proceed. Therefore, the generated ions are more likely to enter, for example, a transport pipe for transporting ions into a vacuum chamber, and the ion collection efficiency is improved. As a result, the amount of ions available for analysis increases, and high analysis sensitivity can be achieved.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0014] The ion analysis apparatus according to the present invention includes a mass spectrometer, an ion mobility spectrometer, and an ion mobility - mass spectrometer combining them. The ion source in the ion analysis apparatus according to the present invention is an ESI ion source, and all configurations other than the ion source, for example, the mass separation method in the mass spectrometer, the presence or absence of an ion dissociation operation and its dissociation method, etc., can be appropriately selected.

[0015] [First Embodiment] A mass spectrometer which is an embodiment of the ion analysis apparatus according to the present invention will be described with reference to the accompanying drawings. FIG. 1 is an overall configuration diagram of the mass spectrometer of the present embodiment. FIG. 2 is a front plan view (A) and a cross - sectional view taken along the line A - AA (B) showing the configuration of the ESI ion source in the mass spectrometer. This mass spectrometer is a single - type atmospheric pressure ionization quadrupole mass spectrometer. For convenience of explanation, as shown in FIGS. 1 and 2, three axes of X, Y, and Z that are perpendicular to each other are defined in space.

[0016] As shown in FIG. 1, the interior of chamber 1 in the mass spectrometer of the present embodiment is partitioned into four parts: 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 in a substantially atmospheric pressure atmosphere, and the inside of the analysis chamber 14 is maintained in a high - vacuum atmosphere by vacuum exhaust using a high - performance vacuum pump (usually a combination of a turbo molecular pump and a rotary pump) not shown in the figure. The inside of the first intermediate vacuum chamber 12 and the second intermediate vacuum chamber 13 are also vacuum - exhausted by vacuum pumps, and it has a configuration of a multi - stage differential exhaust system in which the degree of vacuum increases in order from the ionization chamber 11 toward the analysis chamber 14.

[0017] Inside the ionization chamber 11, an ESI probe 2 for ionization is arranged as an ion source, and a liquid sample containing sample components is sprayed generally in the X-axis direction as fine charged droplets from the ESI probe 2. The charged droplets sprayed from the ESI probe 2 come into contact with the gas in the ionization chamber 11 and are refined. Also, the droplets become smaller due to the active evaporation of the solvent from the droplets. In the process, the sample components in the droplets jump out with charges and become ions.

[0018] The ionization chamber 11 and the first intermediate vacuum chamber 12 communicate with each other through a desolvation tube 3 with a small diameter. The central axis of the ion intake port 3a, which is the opening on the ionization chamber 11 side of the desolvation tube 3, extends substantially parallel to the Z-axis. That is, the spraying direction from the ESI probe 2 and the central axis of the ion intake port 3a (that is, the ion suction direction) are substantially orthogonal. Since there is a pressure difference between both opening ends of the desolvation tube 3, a gas flow is formed from the ionization chamber 11 to the first intermediate vacuum chamber 12 through the desolvation tube 3 due to this pressure difference. The 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 the gas flow, and are discharged into the first intermediate vacuum chamber 12 together with the gas flow.

[0019] Inside the first intermediate vacuum chamber 12, a multipole type ion guide 4 is arranged, and a skimmer 5 having a small hole at the top is provided on the partition wall separating the first intermediate vacuum chamber 12 and the second intermediate vacuum chamber 13. The ions are converged near the small hole of the skimmer 5 by the action of the electric field formed by the ion guide 4, and are sent to the second intermediate vacuum chamber 13 through the small hole.

[0020] Inside the second intermediate vacuum chamber 13, a multipole-type ion guide 6 is also disposed. Due to the action of the electric field formed by the ion guide 6, ions are converged and sent to the analysis chamber 14. Inside the analysis chamber 14, a quadrupole mass filter 7 and an ion detector 8 are arranged. Ions are introduced into the space in the major axis 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 corresponding to the amount of the reached ions and sends it to a data processing unit (not shown). In this mass spectrometer, the analysis sensitivity can be improved by sending a larger amount of ions into the quadrupole mass filter 7, that is, by subjecting them to analysis.

[0021] Next, with reference to FIG. 2, the configuration of the ESI probe 2 will be described in detail. FIG. 2(A) is a view of the ESI probe 2 as seen from the front in the advancing direction of the spray flow of charged droplets. FIG. 2(B) is a cross-sectional view taken along the line A-AA in FIG. 2(A).

[0022] As shown in FIG. 2(A), the ESI probe 2 includes eight conductive capillaries 211 to 218 that are arranged at substantially the same angular intervals (45° angular intervals in this example) on the same circumference U and extend in a direction parallel to the axis S of the circle, and, for each of the eight capillaries 211 to 218, cylindrical nebulizing gas tubes 221 to 228 having a double-tube structure concentric with each capillary 211 to 218. Further, the ESI probe 2 includes a cylindrical auxiliary electrode 23 that extends 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 to 218 are arranged. The tip of the auxiliary electrode 23 protrudes in the X-axis direction from the tips of the capillaries 211 to 218.

[0023] That is, in the ESI probe 2, one auxiliary electrode 23 is arranged to be surrounded by eight capillaries 211 to 218. The distances between the auxiliary electrode 23 and each of the eight capillaries 211 to 218 are substantially the same. The structure of one capillary and the nebulizing Gas tube is the same as the structure of the capillary and the nebulizing Gas tube in a conventional general ESI probe.

[0024] The auxiliary electrode 23 is grounded and its potential is fixed at zero. A DC high voltage of, for example, several kV or more is applied from the DC high voltage power supply 24 to each of the capillaries 211 to 218. The polarity of this voltage is the same as the polarity of the ions to be measured. When the object to be measured is positive ions, a positive-polarity DC high voltage Vh is applied to the capillaries 211 to 218 (however, to avoid complicating the drawing, only the voltage application line connected to one capillary 214 is drawn in Fig. 2(A)).

[0025] The ion generation operation in the ESI probe 2 will be described. Here, as an example, it is assumed that the object to be measured is positive ions. Although not shown, for example, when a liquid sample containing a compound separated by a column of a liquid chromatograph is supplied to the ESI probe 2, this liquid sample is distributed to the eight capillaries 211 to 218 in substantially equal amounts and reaches the tip ends of the capillaries 211 to 218. On the other hand, an appropriate inert gas is supplied as the nebulizing gas to the nebulizing gas tubes 221 to 228.

[0026] When a high voltage of positive polarity is applied to the capillaries 211 to 218, an electric field of strong intensity is formed near the tip of each of the capillaries 211 to 218 due to the potential difference between the auxiliary electrode 23 with a potential of zero and each of the capillaries 211 to 218. In a general ESI ion source, the potential (usually, the ground potential) serving as the reference for the potential of the capillary is the potential near the inlet end of the desolvation tube 3 in FIG. 1. In contrast, in the mass spectrometer of the present embodiment, an auxiliary electrode 23 having a reference ground potential is disposed in the vicinity of the capillaries 211 to 218. Therefore, the intensity of the electric field formed near the tip of each of the capillaries 211 to 218 is strong, and the Coulomb repulsion acting on the charged droplets formed at the tips of the capillaries 211 to 218 becomes large. As a result, the charged droplets are easily miniaturized, and with the help of the nebulizing gas, a large amount of fine charged droplets are sprayed from each of the capillaries 211 to 218.

[0027] By using a plurality of capillaries and disposing an auxiliary electrode having a reference potential in the vicinity of the capillaries, although a large amount of fine charged droplets are sprayed, since these charged droplets are charged with the same polarity, a Coulomb repulsion acts between the charged droplets. Therefore, if there is no influence of an external electric field, the spray flow of the charged droplets spreads in a direction orthogonal to its axis as it progresses, making it difficult to efficiently suck the ions generated from the charged droplets into the desolvation tube 3.

[0028] In contrast, in the mass spectrometer of the present embodiment, since the potential of the auxiliary electrode 23 disposed on the axis S is lower than the potentials of the surrounding capillaries 211 to 218, a potential gradient is formed from the surroundings toward the axis S in the plane (Y-Z plane) orthogonal to the axis S. That is, in front of the tips of the capillaries 211 to 218, a converging electric field is formed that converges positively charged particles (charged droplets, ions) near the axis S. Charged droplets sprayed from the capillaries 211 to 218 and ions generated from the charged droplets receive a force in the direction approaching the axis S, as indicated by the thick arrows in FIG. 2(B), due to this converging electric field. Therefore, the spray flow containing charged droplets and ions is suppressed from spreading due to the Coulomb repulsion, and the ions generated therefrom are efficiently sucked into the desolvation tube 3.

[0029] As described above, in the mass spectrometer of the present embodiment, the auxiliary electrode 23 has the function of enhancing the electric field strength near the tip portions of the capillaries 211 to 218 and the function of converging the spray flow containing charged droplets and ions near the axis S. Thereby, 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, and the generated ions can be more efficiently taken into the desolvation tube 3 and sent to the subsequent stage.

[0030] [First Modification of the First Embodiment] FIGS. 3 and 4 are diagrams showing a modification of the ESI probe 2 in the mass spectrometer of the above embodiment. Although only a part of the capillaries 211 to 218 and the nebulizing gas tubes 221 to 228 are shown, these configurations are the same as those shown in FIG. 2.

[0031] The ESI probe 2A shown in FIG. 3 includes a donut-shaped heating gas supply unit 25 arranged so as to surround a plurality of capillaries 211 to 218. This heating gas supply unit 25 has heating gas ejection ports 251 that are continuous around the entire circumference of the axis S or provided at predetermined angular intervals around the axis S. The heating gas ejection ports 251 are provided to be inclined inward so that the ejected gas is directed toward the axis S. Therefore, the heating gas ejected from the heating gas ejection ports 251 surrounds the spray flow of charged droplets and hits the outer periphery thereof.

[0032] In the ESI probe 2A, due to the combined action of 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 to 228, charged droplets with a small mobility, that is, large-sized charged droplets, are more likely to be located on the outer peripheral side of the spray flow P, showing a droplet distribution like this. Since Coulomb repulsion hardly acts inside large-sized charged droplets, it is difficult for them to be refined and the ionization efficiency is also difficult to increase.

[0033] On the other hand, the heating gas ejected from the heating gas ejection ports 251 efficiently hits the large-sized charged droplets located on the outer peripheral part of the spray flow P. Therefore, it is possible to promote the vaporization of the solvent of such charged droplets and to promote the refinement and ion generation of the droplets. As a result, in the ESI probe 2A according to this modification example, the ionization efficiency can be further enhanced.

[0034] On the other hand, the ESI probe 2B shown in FIG. 4 includes a heating gas supply unit 26 that ejects heating gas so as to cross the spray flow P of charged droplets from a plurality of capillaries 211 to 218. Also in this configuration, the heating gas efficiently hits the large-sized charged droplets located on the outer peripheral part of the spray flow P, and it is possible to promote the vaporization of the solvent from the charged droplets.

[0035] [Second Modification Example of the First Embodiment] In the ESI probes 2, 2A, and 2B of the mass spectrometer according to the above-described embodiment, a plurality of capillaries 211 to 218 are arranged on a substantially identical circumference U at substantially identical angular intervals. As a result, charged droplets of a generally equal amount are sprayed in the circumferential direction around the auxiliary electrode 23. However, the amount of ions sucked into the desolvation tube 3 generated from the charged droplets thus sprayed is unlikely to be uniform in the circumferential direction around the auxiliary electrode 23. One of the reasons is that the partition wall separating the desolvation tube 3 and the ionization chamber 11 from the first intermediate vacuum chamber 12 is at a ground potential or a potential close thereto (a potential much closer to the ground potential than at least the potentials of the capillaries 211 to 218), so that the ion generation efficiency is relatively low in the spray flow from the capillaries located close to the desolvation tube 3 or the partition wall. Another reason is that although there is a converging action due to the electric field by the auxiliary electrode 23, the charged droplets sprayed from the ESI probe 2 and the ions generated therefrom are not focused in a beam shape, so that the ions generated from the spray flow by the capillary located close to the desolvation tube 3 (the capillary located in the positive direction of the Z axis in FIG. 1) are relatively difficult to be sucked into the desolvation tube 3.

[0036] In addition, there is also a problem that charged droplets sprayed from a capillary located close to the desolvation tube 3 and the ions generated therefrom are likely to adhere to the ion intake port 3a of the desolvation tube 3 or the outer surface of the pipeline and cause contamination. A modified example of the mass spectrometer according to the above-described embodiment shown in FIG. 5 can address such problems. FIG. 5 is a front plan view (A) and a cross-sectional view taken along the line A-AA (B) of the ESI probe 2C of this modified example. In FIG. 5, the desolvation tube 3 not described in FIG. 2 is also partially described. In the figure, the same components as those shown in FIG. 2 are denoted by the same reference numerals, and description is omitted unless particularly necessary.

[0037] In this ESI probe 2C, the eight capillaries 211 to 218 are arranged on the same circumference U. In the range from capillary 211 to capillary 218 in the clockwise direction in Fig. 5(A), the angular intervals between two adjacent capillaries in the circumferential direction are 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 80°, which is twice the former. The eight capillaries 211 to 218 of the ESI probe 2C can also be regarded as a state in which one capillary has been removed from a state where nine capillaries including the eight are arranged on the same circumference U at equal angular intervals. The removed capillary is a capillary such that the desolvation tube 3 is exactly at a position on the extension line of the central axis of the capillary.

[0038] Therefore, as shown in Fig. 5(A), when looking at the positional relationship between the desolvation tube 3 and the multiple capillaries 211 to 218 in the Y-Z plane, the desolvation tube 3 is located at a position where the multiple capillaries 211 to 218 do not exist, that is, at a location where the interval between two adjacent capillaries on the circumference U in the circumferential direction is wide. Also, in the Y-Z plane, in order to hold the auxiliary electrode 23 and apply a ground potential to the auxiliary electrode 23, a conductive electrode holding portion 28 that is substantially integrated with the auxiliary electrode 23 is arranged at a position where it overlaps the desolvation tube 3 and is separated in the negative direction of the X axis.

[0039] By applying a DC high voltage Vh to each of the capillaries 211 to 218, a strong electric field is formed near the tip of each of the capillaries 211 to 218. The liquid sample distributed to each of the capillaries 211 to 218 is charged by this electric field and sprayed as minute charged droplets with the aid of nebulizing gas. This is the same as the mass spectrometer of the above-described embodiment. In the mass spectrometer of this modification, each of the capillaries 211 to 218 is relatively far from the desolvation tube 3, and the electric field formed near the tip of each of the capillaries 211 to 218 is less affected by the potential of the desolvation tube 3 or the partition wall. Therefore, charged droplets are favorably generated in each of the capillaries 211 to 218, and ionization is efficiently performed. Further, since the desolvation tube 3 does not exist in front of the spray flow from any of the capillaries 211 to 218, fine charged droplets in the spray flow and ions generated from the spray flow do not adhere to the ion intake port 3a or the pipeline of the desolvation tube 3 and are easily sucked into the desolvation tube 3. Therefore, the ion collection efficiency is also improved.

[0040] As a result, a larger amount of ions can be sent to the subsequent stage, and high analysis sensitivity can be achieved. Further, contamination due to the adhesion of charged droplets and ions to the ion intake port 3a and the pipeline of the desolvation tube 3 can be reduced. Thereby, the performance of the apparatus can be maintained over a long period of time, and the burden of maintenance work of the apparatus can be reduced. Furthermore, by positioning the electrode holding portion 28 that holds the auxiliary electrode 23 in a space where a wide interval between adjacent capillaries is ensured, the auxiliary electrode 23 can be stably held while surely ensuring the electrical insulation between the electrode holding portion 28, each of the capillaries 211 to 218, and the nebulizing gas tubes 221 to 228.

[0041] It is obvious that in this modification as well, a configuration in which the heating gas supply portions 25 and 26 as shown in FIGS. 3 and 4 are added can be adopted. In addition, it is not essential that the intervals between adjacent capillaries be at equal angular intervals at locations other than where a large space is provided. Also, the central axis of the ion intake port 3a of the solvent removal tube 3 and the axis S of the ESI probe 2C may be skew instead of orthogonal.

[0042] [Other modifications] Also, the configurations of the ESI probes 2, 2A, 2B, and 2C in the above-described embodiments and modification examples can be variously modified. For example, the number of capillaries is not limited to the above description and can be appropriately determined as long as there are a plurality of them. Also, it is not essential to arrange the plurality of capillaries 211 to 218 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 intensity of the electric field formed near the tip of the capillary varies, and the variation in the size of the charged droplets sprayed from the capillary also increases. Therefore, in order to make the sizes of the charged droplets as uniform as possible and improve the ionization efficiency, it is better if the distances between each of the plurality of capillaries 211 to 218 and the auxiliary electrode 23 are as the same or close as possible.

[0043] Also, the shape of the auxiliary electrode 23 is not limited to the cylindrical shape as described above. In particular, the shape of the tip of the auxiliary electrode 23 is not a planar shape parallel to the Y-Z plane, but can be an appropriate shape such as a hemispherical shape, etc., to adjust the potential gradient of the converging electric field and improve the convergence of the spray flow.

[0044] Also, the auxiliary electrode 23 is not limited to one, and a plurality of auxiliary electrodes may be provided. FIG. 6 is a diagram showing a modification example in which one auxiliary electrode 231 to 238 is provided corresponding to each of the eight capillaries 211 to 218. This figure is a front plan view when the ESI probe 2 is viewed from the same perspective as in FIG. 2(A). Even in such a configuration, a strong DC electric field can be formed near the tip of each of the capillaries 211 to 218, and an electric field can be formed to converge the spray flow of the charged droplets ejected from each of the capillaries 211 to 218 near the axis S.

[0045] [Second Embodiment] Next, a mass spectrometer, which is another embodiment of the ion analyzer according to the present invention, will be described. Since the overall configuration of this mass spectrometer is the same as that of the device in the first embodiment, the description thereof will be omitted. FIG. 7 is a front plan view (A) and a cross-sectional view taken along the line A-AA (B) showing the configuration of the ESI ion source in the mass spectrometer of this embodiment. In FIG. 7, the same reference numerals are given to the components that are substantially the same as the components of the ESI ion source in the mass spectrometer of the first embodiment, and the description will be omitted unless particularly necessary.

[0046] In the ESI probe 2E of this ESI ion source, the configuration and arrangement of the capillaries 211 to 218 and the nebulizing gas tubes 221 to 228 are the same as those in the first embodiment, but the shape and arrangement of the auxiliary electrode, and further the voltage applied are different from those in the first embodiment. That is, the auxiliary electrode 27 is a substantially cylindrical conductor arranged so as to surround the capillaries 211 to 218. The axis of this auxiliary electrode 27 coincides with the axis S of the circle in which the eight capillaries 211 to 218 are arranged. Therefore, also in this embodiment, the distances between the auxiliary electrode 27 and each of the capillaries 211 to 218 are substantially the same.

[0047] All of the eight capillaries 211 to 218 are grounded (however, in order to avoid complication of the drawing, only the ground wire connected to one capillary 215 is drawn in FIG. 7(A)). On the other hand, a DC high voltage of, for example, several kV or more is applied to the auxiliary electrode 27 from the DC high 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, it is a DC high voltage of positive polarity.

[0048] When a liquid sample is introduced into each of the capillaries 211 to 218 and a positive DC high voltage is applied to the auxiliary electrode 27, since each of the capillaries 211 to 218 is close to the auxiliary electrode 27, a strong electric field is formed near the tip of each of the capillaries 211 to 218. As a result, the charged droplets formed at the tips of the capillaries 211 to 218 are easily miniaturized, and with the help of the nebulizing gas, a large amount of fine charged droplets are sprayed from each of the capillaries 211 to 218.

[0049] These charged droplets have positive charges, but since a positive high voltage is applied to the auxiliary electrode 27 surrounding the eight capillaries 211 to 218, an electric field is formed that exerts a force to push the positively charged droplets (and positive ions ejected from the droplets) toward the inner peripheral side, that is, in the direction approaching the axis S. As a result, as in the first embodiment, although there is a Coulomb repulsion between the charged droplets, the spray flow of the charged droplets is not 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.

[0050] Also in this second embodiment, various modifications similar to those in the first embodiment are possible. That is, similar to the configurations shown in FIGS. 3 and 4, a donut-shaped heating gas supply portion 25 may be added to the outer peripheral side of the auxiliary electrode 27, or a heating gas supply portion 26 that ejects heating gas so as to cross the spray flow P of the charged droplets from the plurality of capillaries 211 to 218 may be added. Also, the number and arrangement of the capillaries may be appropriately changed. The shape of the auxiliary electrode 27 is not limited to a cylindrical shape, and the auxiliary electrode 27 may be appropriately divided into a plurality of parts.

[0051] Also, the above first and second embodiments, and their modified examples are merely examples of the present invention, and it is natural that any changes, modifications, and additions made within the scope of the gist of the present invention are included in the scope of the claims of this application.

[0052] For example, although the above-described embodiment is a single-type quadrupole mass spectrometer, as described above, the mass separation method, the presence or absence of an ion dissociation operation, and the dissociation method can be appropriately selected. Therefore, the present invention can be applied to various mass spectrometers such as a time-of-flight mass spectrometer, an ion trap mass spectrometer, a triple quadrupole mass spectrometer, a quadrupole-time-of-flight mass spectrometer, and an ion trap time-of-flight mass spectrometer. This is of course.

[0053] In addition, since the present invention is applicable to apparatuses in general that ionize and analyze sample components using an ESI ion source, it is not limited to mass spectrometers, and may be an ion mobility analyzer, an ion mobility-mass spectrometer that combines an ion mobility analyzer and a mass spectrometer, or the like.

[0054] [Various Aspects] Those skilled in the art will understand that the above-described exemplary embodiments are specific examples of the following aspects.

[0055] (Item 1) One aspect of the ion analyzer according to the present invention is an ion analyzer including an ion source using the ESI method, wherein the ion source a plurality of capillaries that spray a 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 DC high voltage based on the potential of the one or more auxiliary electrodes to the plurality of capillaries, and is provided with.

[0056] (Item 10) Another aspect of the ion analyzer according to the present invention is an ion analyzer including an ion source using the ESI method, wherein the ion source a plurality of capillaries that spray a supplied liquid sample in the same direction, one or more auxiliary electrodes arranged so as to surround the plurality of capillaries, a voltage application unit that applies a DC high voltage based on the potential of the plurality of capillaries to the one or more auxiliary electrodes, is provided.

[0057] In the ion analyzer according to the first and tenth aspects, a liquid sample containing a component to be analyzed is distributed to a plurality of capillaries, and charged droplets are sprayed from each capillary. Thereby, the amount of the entire liquid sample introduced into the ion source can be increased, and the analysis throughput can be improved. Alternatively, the amount of the liquid sample flowing through one capillary can be reduced, whereby the sprayed droplets can be miniaturized to promote ion generation.

[0058] Further, in the ion analyzer according to the first and tenth aspects, since the auxiliary electrode is disposed in the vicinity of the capillary, the electric field strength near the tip of the capillary is enhanced. Thereby, the charge separation of the liquid sample reaching the capillary tip is promoted, and the ionization efficiency is improved. 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 converge and proceed. Therefore, the generated ions easily enter, for example, a transport pipe for transporting ions into a vacuum chamber, and the ion collection efficiency is improved. Thereby, the amount of ions used for analysis is increased, and high analysis sensitivity can be achieved.

[0059] (Second and eleventh aspects) In the ion analyzer according to the first or tenth aspect, the ion source may further include a nebulizing gas pipe that is provided individually for the plurality of capillaries and ejects nebulizing gas in the same direction as the spraying direction of the liquid sample from the capillary.

[0060] According to the ion analyzer according to the second and eleventh aspects, charged droplets can be sprayed well from the tip of the capillary.

[0061] (Third aspect) In the ion analyzer according to the first or second aspect, the plurality of capillaries are arranged on substantially the same circumference, The auxiliary electrode can be one and can be arranged at a substantially central position of a circle where the plurality of capillaries are arranged.

[0062] (Item 12) Similarly, in the ion analyzer according to Item 10 or 11, the plurality of capillaries are arranged on a substantially same circumference, the auxiliary electrode can be one and can be in a cylindrical shape coaxial with the circle where the plurality of capillaries are arranged.

[0063] In the ion analyzers according to Item 3 and Item 12, since the electric field strength near the tip of each capillary is substantially the same, charged droplets that are similarly miniaturized can be sprayed from each capillary. Thereby, the ionization efficiency can be increased. Also, in the ion analyzers according to Item 3 and Item 12, due to the potential of each capillary and the potential of the auxiliary electrode, the potential gradient of the electric field in the region where the spray flow of the charged droplets is formed is substantially rotationally symmetric around the axis of the spray flow. Thereby, the spray flow of the charged droplets is likely to converge near its axis, and the utilization efficiency of the ions generated from the charged droplets is improved. By such means, a larger amount of ions can be used for analysis, and the analysis sensitivity can be further improved.

[0064] (Item 4) The ion analyzer according to Item 3 collects ions generated from the spray flow from the plurality of capillaries and transports them to the subsequent stage, has an ion intake port in front of the spray flow, and includes an ion transport pipe including a pipe extending in a direction intersecting the direction of the spray from the capillaries. The plurality of capillaries can be arranged on a substantially same circumference and can be arranged except at a position where the ion transport pipe exists on the extension of the direction of the spray.

[0065] (Item 5) Further, in the ion analyzer according to Item 4, the pipe of the ion transport pipe can extend in a direction substantially orthogonal to the direction of the spray from the capillaries.

[0066] Generally, since the ion transport tube is set to the ground potential or a potential relatively close thereto, due to its influence, the electric field formed at the capillary tip in the vicinity of the ion transport tube is liable to weaken. In addition, charged droplets sprayed from the capillary located near the ion transport tube and ions generated thereby are unlikely to ride on the gas flow flowing into the ion transport tube and are unlikely to be taken into the ion transport tube. On the other hand, according to the ion analyzer described in Items 4 and 5, since all of the plurality of capillaries are arranged relatively far from the ion transport tube, a strong electric field is formed in the vicinity of the capillary tip portion, and charged droplets are favorably generated. Further, fine charged droplets contained in the spray flow and ions generated therefrom are efficiently taken into the ion transport tube. As a result, more ions can be sent to the subsequent stage, and the analysis sensitivity can be enhanced. Further, it is possible to reduce the adhesion of charged droplets and ions to the ion transport tube and its ion intake port and prevent contamination.

[0067] (Item 6) In the ion analyzer according to Item 4 or 5, the plurality of capillaries are arranged such that the interval between the capillaries adjacent in the circumferential direction on the circumference is the widest at the position where the ion transport tube exists on the extension in the direction of the spray, It is possible to arrange a holding portion for holding the auxiliary electrode and / or wiring for applying a potential to the auxiliary electrode in the space where the interval between the adjacent capillaries is the widest.

[0068] According to the ion analyzer described in Item 6, it is possible to arrange the holding portion of the auxiliary electrode and the wiring in a sufficiently wide space between the adjacent capillaries, and to sufficiently ensure the electrical insulation between the holding portion or the wiring and the capillary.

[0069] (Item 7, Item 13) The ion analyzer according to any one of Items 1 to 6, or any one of Items 10 to 12 may further include a heating gas supply unit that blows a heating gas to the outside so as to surround the spray flow from the plurality of capillaries.

[0070] In the ion analyzer according to claim 7 and claim 13, the heating gas ejected from the heating gas supply unit mainly hits the outer peripheral side portion of the spray flow of the charged droplets ejected from the plurality of capillaries. Although charged droplets of relatively large size exist in this portion, since the vaporization of the solvent in such charged droplets is promoted, it is effective for increasing the ionization efficiency. Further, since a heating gas flow is formed so as to surround the spray flow of the charged droplets, the spread of the spray flow can be further suppressed, and the utilization efficiency of ions is also further improved.

[0071] (Claim 8, Claim 14) The ion analyzer according to any one of claims 1 to 6, or any one of claims 10 to 12 may further include a heating gas supply unit that blows a heating gas so as to intersect the spray flow from the plurality of capillaries.

[0072] In the ion analyzer according to claim 8 and claim 14, the heating gas ejected from the heating gas supply unit mainly hits the outer peripheral side portion of the spray flow of the charged droplets ejected from the plurality of capillaries. Although charged droplets of relatively large size exist in this portion, since the vaporization of the solvent in such charged droplets is promoted, it is effective for increasing the ionization efficiency.

[0073] (Claim 9, Claim 15) The ion analyzer according to any one of claims 1 to 8, or any one of claims 10 to 14 may be a single type quadrupole mass spectrometer, a triple quadrupole mass spectrometer, or a quadrupole-time-of-flight mass spectrometer having the ion source.

[0074] In such a mass spectrometer, it is necessary to transport ions from an ion source in an atmospheric pressure atmosphere to a subsequent vacuum chamber through a desolvation tube, a sampling cone, etc. However, in the mass spectrometer according to claim 9 and claim 15, the ions generated in the ion source can be efficiently collected and transported to the subsequent stage. Thereby, according to the mass spectrometer according to claim 9 and claim 15, high analysis sensitivity can be achieved.

Explanation of Symbols

[0075] 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…Heating Gas Supply Section 251…Heating Gas Outlet 28…Electrode Holder 3…Desolvation Tube 4, 6…Ion Guide 5…Skimmer 7…Quadrupole Mass Filter 8…Ion Detector

Claims

1. An ion analyzer comprising an ion source using an electrospray ionization method, wherein the ion source includes a plurality of capillaries that spray a 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 DC high voltage with reference to the potential of the one or more auxiliary electrodes to the plurality of capillaries, and an ion analyzer comprising the same.

2. The ion source further includes a nebulizing gas pipe provided individually for the plurality of capillaries and ejecting nebulizing gas in the same direction as the spraying direction of the liquid sample from the capillaries. The ion analyzer according to claim 1.

3. The plurality of capillaries are arranged on a substantially same circumference, the auxiliary electrode is one and is arranged at a substantially central position of the circle on which the plurality of capillaries are arranged. The ion analyzer according to claim 1 or 2.

4. It collects ions generated from the spray flows from the plurality of capillaries and transports them to the subsequent stage. It has an ion intake port in front of the spray flow and includes an ion transport pipe including a pipe extending in a direction intersecting the spraying direction from the capillaries. The plurality of capillaries are on a substantially same circumference and are arranged except at a position where the ion transport pipe exists on the extension of the spraying direction. The ion analyzer according to claim 3.

5. The pipe of the ion transport pipe extends in a direction substantially orthogonal to the spraying direction from the capillaries. The ion analyzer according to claim 4.

6. The plurality of capillaries are arranged such that the interval between adjacent capillaries in the circumferential direction on the circumference is the widest at a position where the ion transport pipe exists on the extension of the spraying direction. A holding part for holding the auxiliary electrode and / or wiring for applying a potential to the auxiliary electrode are arranged in the space where the interval between the adjacent capillaries is the widest. The ion analyzer according to claim 4 or 5.

7. The ion analyzer according to any one of claims 1 to 6 further includes a heating gas supply unit that blows heating gas to the outside so as to surround the spray flows from the plurality of capillaries.

8. The ion analysis device according to any one of claims 1 to 6, further comprising a heating gas supply unit that blows a heating gas so as to intersect the spray flow from the plurality of capillaries.

9. The ion analysis device according to any one of claims 1 to 8, which is a single type quadrupole mass spectrometer, a triple quadrupole mass spectrometer, or a quadrupole-time-of-flight mass spectrometer having the ion source.

10. An ion analysis device comprising an ion source using an electrospray ionization method, wherein the ion source a plurality of capillaries that spray a supplied liquid sample in the same direction, one or more auxiliary electrodes arranged so as to surround the plurality of capillaries, a voltage application unit that applies a DC high voltage based on the potential of the plurality of capillaries to the one or more auxiliary electrodes, An ion analysis device comprising.

11. The ion analysis device according to claim 10, further comprising a nebulizing gas tube that is provided individually for the plurality of capillaries and ejects a nebulizing gas in the same direction as the spray direction of the liquid sample from the capillaries.

12. The plurality of capillaries are arranged on a substantially same circumference, The ion analysis device according to claim 10 or 11, wherein there is one auxiliary electrode, and the auxiliary electrode has a cylindrical shape coaxial with the circle on which the plurality of capillaries are arranged.

13. The ion analysis device according to any one of claims 10 to 12, further comprising a heating gas supply unit that blows a heating gas to the outside so as to surround the spray flow from the plurality of capillaries.

14. The ion analysis device according to any one of claims 10 to 12, further comprising a heating gas supply unit that blows a heating gas so as to intersect the spray flow from the plurality of capillaries.

15. The ion analysis device according to any one of claims 10 to 14, which is a single type quadrupole mass spectrometer, a triple quadrupole mass spectrometer, or a quadrupole-time-of-flight mass spectrometer having the ion source.

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