Ionization device

Abstract

An ionization device disposed in an ionization chamber separated from an analysis chamber by a partition wall having an ion introduction opening, the ionization device comprising an electrospray ionization probe 111 that is disposed such that the spray axis thereof is orthogonal to the central axis of the ion introduction opening, charges a liquid sample, and sprays the liquid sample as charged droplets, and a heated gas supply mechanism that blows heated gas onto a position that is between the distal end of the electrospray ionization probe and the point of intersection X between the spray axis and the central axis at least at a prescribed distance from the distal end.

Description

Technical Field

[0001] The present invention relates to an ionization device.

Background Art

[0002] In order to measure a target component contained in a liquid sample, a liquid chromatography mass spectrometer is widely used. In the measurement of a target component using a liquid chromatography mass spectrometer, a liquid sample is introduced into a liquid chromatograph, the target component is separated by a column of the liquid chromatograph, and then introduced into a mass spectrometer. In the mass spectrometer, for example, a target component contained in a liquid sample is ionized by an ESI (ElectroSpray Ionization) source, and the generated ions are separated and detected according to the mass-to-charge ratio.

[0003] The ESI source includes a capillary to which a high voltage is applied and through which a liquid sample flows, and an ESI probe having a nebulizer gas flow path provided on the outer periphery of the capillary. In the ESI probe, a liquid sample flowing through the capillary is charged by the high voltage and transported to the tip of the ESI probe, and a nebulizer gas is sprayed at the tip to spray the liquid sample into the ionization chamber as charged droplets. The charged droplets sprayed into the ionization chamber are repeatedly refined through a process in which the surface electric field increases as the solvent evaporates (desolvation) and they split due to the repulsion between charges, and finally ionize. The ions generated in the ionization chamber are drawn into the mass spectrometry chamber through an ion inlet provided in the partition wall between the ionization chamber and the mass spectrometry chamber due to the pressure difference between the ionization chamber, which is at approximately atmospheric pressure, and the mass spectrometry chamber, which is a vacuum chamber located at the subsequent stage. Patent Documents 1 and 2 describe an ionization device provided with a mechanism for spraying a heating gas onto charged droplets in addition to the ESI probe in order to promote desolvation in such an ionization process.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] Patent documents 1 and 2 describe blowing a heating gas near the tip of the ESI probe, which allows for efficient heating of the charged droplet immediately after it is sprayed from the probe. However, this method has the problem that the liquid sample flowing through the capillary inside the ESI probe is heated and boils, causing the spray from the ESI probe to become unstable and resulting in unstable ion measurement sensitivity.

[0006] The problem that this invention aims to solve is to promote solvent removal without destabilizing the ionization efficiency of the target component in an ionization apparatus that ionizes a target component contained in a liquid sample by electrospray ionization. [Means for solving the problem]

[0007] The present invention, made to solve the above problems, is an ionization apparatus arranged in an ionization chamber separated from an analysis chamber by a partition wall provided with an ion inlet, An electrospray ionization probe is used to charge a liquid sample and spray it as charged droplets, with the spray axis positioned perpendicular to the central axis of the ion inlet. A heating gas supply mechanism is provided, which is located at a predetermined distance or more from the tip of the electrospray ionization probe, and sprays heating gas at a position between the tip and the intersection of the spray axis and the central axis. It is equipped with. [Effects of the Invention]

[0008] In the ionization apparatus according to the present invention, a heating gas is blown onto charged droplets that have been atomized while flying a predetermined distance or more after being sprayed from the tip of an electrospray ionization (ESI) probe. As a result, solvent molecules contained in the charged droplets are rapidly released, promoting desolvation. Furthermore, since the heating gas is blown at a position spaced away from the tip of the ESI probe, the liquid sample does not boil while passing through the capillary inside the ESI probe, and desolvation from the charged droplets is promoted. That is, the above predetermined distance is a distance that takes into account the spread of the jet of heating gas blown from the heating gas supply mechanism, so that the heating gas is not blown directly onto the ESI probe. When the ions generated by blowing the heating gas approach the central axis, they are drawn into the analysis chamber from the ion inlet due to the pressure difference between the ionization chamber and the analysis chamber. Furthermore, since the heating gas is blown before the charged droplets sprayed from the tip of the ESI probe reach the ion inlet, the entry of the charged droplets into the analysis chamber from the ion inlet while still in droplet form is suppressed. Furthermore, supplying heating gas to this location prevents substances other than ions generated from the liquid sample (unwanted neutral molecules or ions present in the ionization chamber) from entering the analysis chamber through the ion inlet. Consequently, contamination of the ion inlet and analysis chamber is suppressed, and the robustness of the device is improved. [Brief explanation of the drawing]

[0009] [Figure 1] A schematic diagram of a liquid chromatograph-mass spectrometer, which combines a mass spectrometer containing one embodiment of the ionization device according to the present invention with a liquid chromatograph. [Figure 2] An enlarged view of the tip of the ESI probe of the ionization apparatus in this embodiment. [Figure 3] A diagram illustrating the parameters related to the arrangement of the ionization apparatus in this embodiment. [Figure 4] Measurement results using the ionizer configuration of the example and the ionizer configuration of the comparative example. [Figure 5] A diagram illustrating another measurement result using the ionization apparatus of this embodiment. [Modes for carrying out the invention]

[0010] Embodiments of the ionization apparatus according to the present invention will be described below with reference to the drawings. Figure 1 is a schematic diagram of a liquid chromatograph-mass spectrometer 100 equipped with the ionization apparatus of this embodiment.

[0011] The liquid chromatograph-mass spectrometer 100 of this embodiment comprises, broadly speaking, a liquid chromatograph 2, a mass spectrometer 1, and a control / processing unit 3 that controls each of these parts.

[0012] The mass spectrometer 1 comprises an ionization chamber 11 at approximately atmospheric pressure and a vacuum chamber whose interior is evacuated by a vacuum pump (not shown). The inside of the vacuum chamber is divided into a first intermediate vacuum chamber 12, a second intermediate vacuum chamber 13, and an analysis chamber 14, and has a differential pumping system configuration in which the vacuum level increases in this order. The ionization chamber 11 and the first intermediate vacuum chamber 12 are connected by a desolvation tube 113 provided in the partition wall separating them. The first intermediate vacuum chamber 12 and the second intermediate vacuum chamber 13 are connected by an opening at the top of a skimmer 122 provided in the partition wall separating them. The second intermediate vacuum chamber 13 and the analysis chamber 14 are connected by an opening provided in the partition wall separating them.

[0013] The ionization chamber 11 houses an electrospray ionization (ESI) probe 111 and a heating gas supply probe 112. The ESI probe 111 accepts either a liquid sample directly or a liquid sample after component separation by a liquid chromatography column. The heating gas supply probe 112 blows a heating gas onto the charged droplets sprayed from the ESI probe 111. For example, nitrogen gas is used as the heating gas.

[0014] As shown in the partial enlarged view of the tip in FIG. 2, the ESI probe 111 includes a capillary 1111 through which a liquid sample flows and a nebulizer gas flow path 1112 provided outside the capillary 1111. In the ESI probe 111, the liquid sample flowing through the capillary 1111 is charged by the high voltage (ESI voltage) and transported to the tip of the ESI probe 111, and the nebulizer gas is sprayed at the tip, thereby spraying the liquid sample into the ionization chamber 11 as charged droplets. The charged droplets sprayed into the ionization chamber 11 are refined by repeating the process of increasing the surface electric field due to the evaporation (desolvation) of the solvent and splitting due to the repulsion between charges, and finally ionized. Further, the desolvation is promoted by spraying the heating gas from the heating gas supply probe 112 onto the charged droplets. The ions generated in the ionization chamber 11 are drawn into the first intermediate vacuum chamber 12 from the desolvation tube 113 due to the pressure difference in the first intermediate vacuum chamber 12 located in the subsequent stage. The desolvation tube 113 is heated by a heating block 114 that forms a part of the partition wall, and the desolvation is further promoted while passing through the desolvation tube 113. The heating block 114 is heated by energizing a heater (not shown).

[0015] In the first intermediate vacuum chamber 12, an ion guide 121 composed of a plurality of rod-shaped electrodes is arranged. The ions introduced through the desolvation tube 113 are converged near the ion optical axis (central axis in the flight direction of the ions) C by the ion guide 121 and enter the second intermediate vacuum chamber 13 through the opening at the top of the skimmer 122.

[0016] In the second intermediate vacuum chamber 13, an ion guide 131 composed of a plurality of rod-shaped electrodes is arranged. The ions introduced through the opening at the top of the skimmer 122 are converged near the ion optical axis C by the ion guide 131 and enter the analysis chamber 14 through the opening provided in the partition wall separating the second intermediate vacuum chamber 13 and the analysis chamber 14.

[0017] In the analysis chamber 14, a front-stage quadrupole mass filter 141, a collision cell 142, a rear-stage quadrupole mass filter 144, and an ion detector 145 are arranged. Both the front-stage quadrupole mass filter 141 and the rear-stage quadrupole mass filter 144 are composed of main rods, pre-rods located in the front stage of the main rods, and post-rods located in the rear stage of the main rods. In the collision cell 142, a multipole rod electrode 143 for converging ions in the collision cell 142 near the ion optical axis C is arranged. Further, the collision cell 142 is provided with a CID gas introduction part for introducing an inert gas such as nitrogen gas as a collision-induced dissociation (CID) gas.

[0018] Among the ions entering the analysis chamber 14, ions having a predetermined mass-to-charge ratio are selected as precursor ions by the front-stage quadrupole mass filter 141 and enter the collision cell 142. Inside the collision cell 142, the precursor ions are cleaved by collision with the CID gas to generate product ions. The ions generated in the collision cell 142 are mass-separated by the rear-stage quadrupole mass filter 144 and detected by the ion detector 145. The output signal from the ion detector 145 is sequentially transmitted to the control and processing unit 3. The control and processing unit 3 creates a mass spectrum based on the output signal from the ion detector 145.

[0019] In the mass spectrometer 1 of the present embodiment, MS scan measurement, selected ion monitoring (SIM) measurement, product ion scan (MS / MS scan) measurement, multiple reaction monitoring (MRM) measurement, etc. can be performed. In the MS scan measurement, the mass-to-charge ratio of the ions passing through the rear-stage quadrupole mass filter 144 is scanned without selecting ions by the front-stage quadrupole mass filter 141 (not functioning as a mass filter), and the ions are detected by the ion detector 145. In the SIM measurement, the mass-to-charge ratio of the ions passing through the rear-stage quadrupole mass filter 144 is fixed without selecting ions by the front-stage quadrupole mass filter 141, and the ions are detected by the ion detector 145.

[0020] On the other hand, in MS / MS scan and MRM measurements, both the pre-stage quadrupole mass filter 141 and the post-stage quadrupole mass filter 144 function as mass filters, with the pre-stage quadrupole mass filter 141 allowing only ions with a set mass-to-charge ratio as precursor ions to pass through. In addition, CID gas is supplied inside the collision cell 142 to cleave the precursor ions and generate product ions. In MS / MS scan measurements, the mass-to-charge ratio of ions passing through the post-stage quadrupole mass filter 144 is scanned and the product ions are detected by the ion detector 145. In MRM measurements, the mass-to-charge ratio of ions passing through the post-stage quadrupole mass filter 144 is fixed and the product ions are detected by the ion detector 145.

[0021] The mass spectrometer 1 of this embodiment is characterized by the arrangement of each part in the ionization chamber 11. The configuration of the ionization chamber 11 will be described below. Figure 3 is an enlarged view of the ionization chamber 11 of the mass spectrometer 1.

[0022] The ESI probe 111 is positioned such that its spray axis (the central axis of the direction of travel of charged droplets sprayed from the ESI probe 111) and the central axis of the desolvation tube 113 are perpendicular at the intersection X. In this embodiment, the most preferred configuration is that the spray axis of the ESI probe 111 is vertical and the central axis of the desolvation tube 113 is horizontal. The heating gas supply probe 112 is positioned such that the angle θ between the spraying direction of the heating gas supply probe 112 (the central axis of the direction of travel of the heating gas) and the spray axis of the ESI probe 111 is between 60 and 80 degrees. The desolvation tube 113, which is a capillary provided in the partition wall between the ionization chamber 11 and the first intermediate vacuum chamber 12, is heated to a predetermined temperature by a heating block 114 that constitutes part of the partition wall.

[0023] Furthermore, the heating block 114 is positioned such that the upper part (the portion located above the desolvation tube 113) is in the direction of the heating gas supply probe 112's spraying. That is, the heating gas supplied from the heating gas supply probe 112 is sprayed onto the charged droplet at a position between the tip of the ESI probe 111 and the intersection X of the spray axis of the ESI probe 111 and the central axis of the desolvation tube 113. In this embodiment, since the heating gas is sprayed on the charged droplet before it reaches the desolvation tube 113, it is suppressed that the charged droplet enters the analysis chamber 14 side (first intermediate vacuum chamber 12, second intermediate vacuum chamber 13, and analysis chamber 14) from the desolvation tube 113 while still in droplet form. In addition, by supplying the heating gas to this position, it is also suppressed that substances other than ions generated from the liquid sample (unwanted neutral molecules and ions present in the ionization chamber 11) enter the analysis chamber 14 side through the desolvation tube 113. This suppresses contamination in each room of the analysis laboratory and improves the robustness of the mass spectrometer 1.

[0024] The above arrangement is based on the results of measurements taken by the inventors to determine the optimal arrangement of the ESI probe 111 and the heating gas supply probe 112. The measurements are described below.

[0025] In this measurement, the liquid chromatograph mass spectrometer 100 of the above embodiment is used, and the distance L from the tip of the ESI probe 111 to the intersection of the spray axis of the ESI probe 111 and the spraying direction of the heating gas supply probe 112 (i.e., the flight distance until the charged droplet sprayed from the ESI probe 111 is heated) and the angle θ are used as parameters (see Figure 3), and the arrangement of different combinations of these values ​​for the embodiments and comparative examples 1 to 5 (see Figure 4) is used to measure the reserpine (C) contained in the liquid sample. 33 H 40 N2O9. MRM transition: 609.3 > 195.1), Testosterone (Testosterone, C 19 H 28 O2. MRM transition: 289.2 > 97.1), and chlorsulfuron (C)12 H 12 ClN5O4S. MRM transition (358.2 > 167.1) was measured using MRM.

[0026] The difference in height between the tip of the ESI probe 111 and the central axis of the desolvation tube 113 (distance in the direction parallel to the spray axis of the ESI probe) was 10.5 mm. In the horizontal direction (parallel to the central axis of the desolvation tube 113), the distance between the tip of the ESI probe 111 and the tip of the heating gas supply probe 112 was 10 mm. In the horizontal direction, the distance between the tip of the ESI probe 111 and the inlet end of the desolvation tube 113 was 0 mm (i.e., they were in the same position). Note that in Figures 1 and 3, the horizontal positions of the tip of the ESI probe 111 and the desolvation tube 113 are offset to make the intersection X easier to understand. In other words, in Examples 1, Comparative Examples 2 and 4, the heated gas was blown onto the charged droplets sprayed from the ESI probe 111 at a position higher than the central axis of the desolvation tube 113 (a position between the tip of the ESI probe 111 and the intersection of the spray axis of the ESI probe 111 and the central axis of the desolvation tube 113), while in Comparative Examples 1, 3, and 5, the heated gas was blown onto the charged droplets sprayed from the ESI probe at a position lower than the central axis of the desolvation tube 113 (on the opposite side of the ESI probe 111).

[0027] In this measurement, a mixed solution of water and acetonitrile (water:acetonitrile = 3:7) was used as the mobile phase of liquid chromatograph 2, and the solution was delivered at a flow rate of 0.2 ml / min. Nitrogen gas was supplied at a flow rate of 3 L / min as a nebulizer gas to spray the liquid sample through ESI probe 111, and a voltage of 3 kV (ESI voltage) was applied to charge the liquid sample. Dry air heated to 400°C was supplied at a flow rate of 5.0 L / min from heating gas supply probe 112. The desolvation tube 113 was heated to 300°C. These measurement conditions were common to both the examples and comparative examples.

[0028] Figure 4 shows the measurement intensity of each substance in each configuration. As shown in Figure 4, for all three substances, the measurement intensity in the configuration of the example was higher than in the configurations of Comparative Examples 1 to 3. From the results of the example and Comparative Example 1, it was found that blowing heated gas onto the charged droplets sprayed from the ESI probe 111 at a position higher than the central axis of the desolvation tube 113 (a position between the tip of the ESI probe 111 and the intersection of the spray axis of the ESI probe 111 and the central axis of the desolvation tube 113) increases the ion measurement intensity (improves measurement sensitivity). Furthermore, from the results of the example and Comparative Examples 2 and 4, it was found that the optimal angle θ between the spray axis of the ESI probe 111 and the blowing direction of the heated gas supply probe 112 is 70 degrees, and that the ion measurement intensity (sensitivity) decreases when this angle exceeds 90 degrees. Furthermore, if the angle θ formed by the spray axis of the ESI probe 111 and the blowing direction of the heating gas supply probe 112 is less than 60 degrees, the tip of the ESI probe 111 and the heating gas supply probe 112 will come into close proximity, potentially causing physical interference and making their placement difficult. The possibility of discharge also increases. On the other hand, if the angle θ exceeds 80 degrees, the heating gas may be blown near the tip of the ESI probe 111, potentially causing the liquid sample flowing through the capillary inside the ESI probe 111 to boil. For these reasons, it is preferable to keep the angle θ formed by the spray axis of the ESI probe 111 and the blowing direction of the heating gas supply probe 112 within the range of 60 degrees to 80 degrees.

[0029] Next, the ion intensity was measured by varying the distance L from the tip of the ESI probe 111 to the intersection of the spray axis of the ESI probe 111 and the spray direction of the heating gas supply probe 112 (i.e., the flight distance until the charged droplet sprayed from the ESI probe 111 is heated) between 2.5 mm and 9.0 mm. In this measurement, the angle θ between the spray axis of the ESI probe 111 and the spray direction of the heating gas supply probe 112 was set to 70 degrees, and the reserpine contained in the liquid sample was measured. The type and flow rate of the mobile phase, nebulizer gas, and heating gas, as well as the temperature of the desolvation tube 113, were the same as in the measurement described above.

[0030] Figure 5 shows the measurement results. In this measurement, when the distance L is 4.5 mm or more, the ion measurement intensity increases as the distance L decreases, and the measurement intensity is the same in the range of 2.5 mm to 4.5 mm. When the distance L is less than 2.5 mm, the heated gas from the heated gas supply probe 112 is also blown onto the tip of the ESI probe 111, which may cause the liquid sample flowing through the ESI probe to boil. This problem can be avoided by narrowing the flow of heated gas blown from the heated gas supply probe 112, but even then, if the distance L is made too small, the tip of the ESI probe 111 and the tip of the heated gas supply probe 112 may come into close proximity and discharge may occur. Considering these points, it is preferable to set the distance L to 2.5 mm or more. Furthermore, ionizers in which the height of the tip of the ESI probe 111 and the height of the central axis of the desolvation tube 113 are 10.5 mm, as in the ionizer of this embodiment, are widely used, for example, in single quadrupole type mass spectrometers. In this configuration of ionization apparatus, in order to blow the heated gas onto the charged droplet at a position higher than the central axis of the desolvation tube 113, it is preferable that the distance L is 10.0 mm or less (at least 0.5 mm higher than the central axis of the desolvation tube 113). That is, it is preferable that the above distance L is 2.5 mm or more and 10 mm or less. In addition, in triple quadrupole type mass spectrometers, ionization apparatuses are also used in which the height of the tip of the ESI probe 111 and the height of the central axis of the desolvation tube 113 are 15.5 mm apart. When using an ionization apparatus in which the height of the tip of the ESI probe 111 differs from that described above, it is sufficient to ensure that the intersection of the spray axis of the ESI probe 111 and the spraying direction of the heated gas supply probe 112 is at least 0.5 mm higher than the central axis of the desolvation tube 113.

[0031] In the ionization apparatus of the above embodiment, the heating gas supply probe 112 is positioned such that the heating block 114 (the part of the heating block 114 above the desolvation tube 113) is located in the direction of the heating gas blown from the heating gas supply probe 112. By adopting this configuration, the heating block 114 is heated by the heating gas from the heating gas supply probe 112, so the amount of power supplied to the heater or the like to heat the heating block 114 can be reduced.

[0032] The above embodiments and measurement examples are merely examples and can be modified as appropriate in accordance with the spirit of the present invention. In the above embodiments, a liquid chromatograph mass spectrometer was used, but it is also possible to directly introduce a liquid sample into the ESI probe without a liquid chromatograph. Furthermore, in the above embodiments, the generated ions were used for mass spectrometry, but an ionization device similar to that in the above embodiments can also be used in devices that perform other measurements, such as ion mobility measurements. In addition, when performing mass spectrometry, various configurations of mass spectrometry units other than the triple quadrupole type of the above embodiments (single quadrupole type, ion trap type, time-of-flight type, etc.) can be used.

[0033] [Aspect] Those skilled in the art will understand that the above-described exemplary embodiments are specific examples of the following embodiments.

[0034] (Section 1) One aspect of the present invention is an ionization apparatus arranged in an ionization chamber separated from an analysis chamber by a partition wall provided with an ion inlet, An electrospray ionization probe is used to charge a liquid sample and spray it as charged droplets, with the spray axis positioned perpendicular to the central axis of the ion inlet. A heating gas supply mechanism that blows heating gas onto the tip of the electrospray ionization probe at a predetermined distance or more away from the tip, at a position between the tip and the intersection of the spray axis and the central axis. It is equipped with.

[0035] In the ionization apparatus described in paragraph 1, a heated gas is blown onto charged droplets that have been atomized as they travel a predetermined distance or more after being sprayed from the tip of the electrospray ionization (ESI) probe. As a result, solvent molecules contained in the charged droplets are rapidly released, promoting desolvation. Furthermore, because the heated gas is blown at a position away from the tip of the ESI probe, the liquid sample does not boil as it passes through the capillary inside the ESI probe, and desolvation from the charged droplets is promoted. That is, the predetermined distance is a distance at which the heated gas is not directly blown onto the ESI probe, taking into account the spread of the jet of heated gas blown from the heated gas supply mechanism. When the ions generated by blowing the heated gas approach the central axis, they are drawn into the analysis chamber from the ion inlet due to the pressure difference between the ionization chamber and the analysis chamber. Furthermore, the heating gas supply mechanism is positioned so that the heating gas is blown onto the charged droplets between the tip of the ESI probe and the intersection of the spray axis from which the ESI probe sprays the charged droplets and the central axis of the ion inlet. Because the heating gas is blown onto the charged droplets sprayed from the tip of the ESI probe before they reach the ion inlet, the entry of the charged droplets into the analysis chamber through the ion inlet while still in droplet form is suppressed. In addition, supplying the heating gas to this position also suppresses the entry of substances other than ions generated from the liquid sample (unwanted neutral molecules and ions present in the ionization chamber) into the analysis chamber through the ion inlet. Consequently, contamination of the ion inlet and analysis chamber is suppressed, and the robustness of the device is improved.

[0036] (Section 2) In the ionization apparatus described in paragraph 1, The central axis of the ion inlet is a horizontal axis. The tip of the electrospray ionization probe is positioned above the ion inlet, and the charged droplet is sprayed downward from the tip.

[0037] In the ionization apparatus described in paragraph 2, charged droplets are sprayed downward from the electrospray ionization probe without resisting gravity. Therefore, even if conditions such as the amount of nebulizer gas supplied differ, the spray direction of the charged droplets does not change significantly, and the position where the heated gas is blown remains constant. Consequently, desolvation and ionization can be promoted stably and reliably. Furthermore, in the ionization apparatus described in paragraph 2, the heated gas is blown onto the downward-moving charged droplets at a position above the ion inlet. This further reduces the risk of the charged droplets reaching the ion inlet in their droplet form and contaminating the analysis room, thus further improving the robustness of the apparatus.

[0038] (Section 3) In the ionization apparatus described in paragraph 1 or 2, The angle between the spray axis and the direction of the heated gas is 60 degrees or more and 80 degrees or less.

[0039] In the ionization apparatus described in paragraph 3, the angle being 60 degrees or more prevents physical interference between the tip of the ESI probe and the probe that blows the heating gas, making it easier to position them. Furthermore, the angle being 80 degrees or less reduces the possibility of the heating gas being blown onto the tip of the ESI probe, which could cause the liquid sample to boil within the probe.

[0040] (Section 4) In the ionization apparatus described in any of paragraphs 1 to 3, The distance from the tip of the electrospray ionization probe to the intersection of the spray axis and the direction of heating gas spraying is 2.5 mm or more and 10 mm or less.

[0041] In the ionization apparatus described in Section 4, by setting the above distance to 2.5 mm or more, the possibility of discharge occurring due to close proximity between the tip of the ESI probe and the tip of the heating gas supply probe can be reduced. Furthermore, by setting the above distance to 10 mm or less, in a common ionization apparatus widely used in which the height of the tip of the ESI probe and the height of the central axis of the desolvation tube are 10.5 mm, the heating gas can be blown onto the charged droplet at a position above the central axis of the desolvation tube to promote desolvation and improve the sensitivity of ion measurement.

[0042] (Section 5) In an ionization apparatus described in any of paragraphs 1 to 4, The ion inlet is the entrance to a desolvation tube that is heated by a heating element that constitutes part of the partition wall, and the heated gas is blown onto the heating element.

[0043] In the ionization apparatus described in paragraph 5, the power consumption required to heat the heating element block can be suppressed by heating the heating element block with a heating gas that promotes solvent removal. [Explanation of symbols]

[0044] 1...Mass spectrometer 11…Ionization Chamber 111...ESI probe 112...Heating gas supply probe 113... Desolvent removal tube 114…Heating block 12…First intermediate vacuum chamber 121... Aeon Guide 122... Skimmer 13…Second Intermediate Vacuum Chamber 131... Aeon Guide 14…Analysis room 141... Pre-stage quadrupole mass filter 142...Collision cell 143…Multipole rod electrode 144...Later stage quadrupole mass filter 145... Ion detector 2…Liquid Chromatography 3…Control and Processing Unit C...Ion optical axis L...Distance from the tip of the ESI probe to the intersection of the spray axis of the ESI probe and the spray direction of the heating gas supply probe. θ…Angle formed by the spray axis of the ESI probe and the spray direction of the heating gas supply probe.

Claims

1. An ionization apparatus is placed in an ionization chamber, which is at approximately atmospheric pressure and separated from a vacuum-evacuated analysis chamber by a partition wall equipped with an ion inlet, An ion introduction tube is provided in the partition wall, the inlet of which is the ion introduction port, A heating member provided in the partition wall for heating the ion introduction tube, An electrospray ionization probe is provided, in which the spray axis is positioned perpendicular to the central axis of the ion inlet, and which charges a liquid sample and sprays it as charged droplets. A heating gas supply mechanism that blows heated gas within an open section from the tip of the electrospray ionization probe to the point where the spray axis and the central axis intersect, such that the central axis in the spraying direction passes through a point located at a predetermined distance or more from the tip. Equipped with, The predetermined distance is set so that the heated gas does not reach the electrospray ionization probe. An ionization apparatus in which the heating gas supply mechanism is arranged such that the central axis of the direction in which the heating gas is blown passes through the heating member, and does not pass through the portion of the ion introduction tube that is exposed to the ionization chamber.

2. The central axis of the ion inlet is a horizontal axis. The ionization apparatus according to claim 1, wherein the tip of the electrospray ionization probe is positioned above the ion inlet, and the charged droplet is sprayed downward from the tip.

3. The ionization apparatus according to claim 1, wherein the angle formed by the spray axis and the central axis of the direction of blowing the heated gas is 60 degrees or more and 80 degrees or less.

4. The ionization apparatus according to claim 1, wherein the distance from the tip of the electrospray ionization probe to the intersection of the spray axis and the central axis of the direction of heating gas spraying is 2.5 mm or more and 10 mm or less.

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