WO2018008063A1 - Electric discharge nozzle for electrospray - Google Patents

Abstract

Disclosed is an electric discharge nozzle for electrospray, said electric discharge nozzle being provided with: a tubular member in which a liquid passes; a needle-like member, which is attached to the center of the tubular member in a state wherein the needle-like member is electrically connected to the tubular member, and which has a leading end section that protrudes from an electric discharge-side end section of the tubular member; and hydrophilic sections that are provided on the surface of the electric discharge-side end section of the tubular member, and on the surface of a needle-like member portion protruding from the electric discharge-side end section.

Description

Discharge nozzle for electrospray

The present invention relates to an electrospray discharge nozzle for spraying a liquid by a so-called electrospray ionization method.

The discharge nozzle for electrospray has a capillary that is a thin tubular member. Then, a high voltage is applied between the discharge nozzle and the counter electrode to make the liquid passing through the tubular member into fine droplets having an excessive charge and sprayed toward the counter electrode. The electrospray ionization method is a liquid spray technique that utilizes the electrospray phenomenon, also called electrostatic spraying, and applies a high voltage between the point-like liquid and the counter electrode to charge the liquid with an excessive charge. In this technique, fine droplets are sprayed toward the counter electrode. In recent years, the liquid spray technology using electrospray ionization has expanded its application range to coating organic EL and biopolymers on substrates, forming nanometer-sized fibers, electrostatic coating, and introducing samples into mass spectrometers. ing.

The electrospray phenomenon is considered as follows, although there are many unclear points. As shown in the principle diagram of FIG. 6, a high voltage of several thousand volts is applied between a metal capillary 50 that is a thin tube and a counter electrode 51, and a liquid 52 that is a sample is caused to flow through the capillary 50. The liquid 52 that comes out at the tip of the capillary 50 forms a liquid pool 52a. A strong electric field toward the counter electrode 51 exists at the tip of the capillary 50. When the capillary 50 side has a positive potential, positive ions in the liquid pool 52a are electrophoresed on the liquid surface side, and negative ions are electrophoresed on the inside. The negative ions electrophoresed on the inside reach the surface of the capillary 50 and cause an oxidation reaction under a high electric field. The negative ions, that is, electrons, are imparted to the capillary 50 to be neutralized. The positive ions that have electrophoresed on the surface of the liquid pool 52 a at the tip receive a strong electromagnetic attraction force toward the counter electrode 51, and the tip of the liquid pool 52 a tends to extend toward the counter electrode 51. On the other hand, surface tension acts on the liquid 52 in the liquid pool 52a. Surface tension is a force that reduces the surface area of a liquid. Therefore, it works in a direction to prevent the tip of the liquid pool 52a from extending.

When the electromagnetic attraction force and the force due to surface tension are balanced, the liquid pool 52a at the tip of the capillary 50 has a conical shape with a vertex angle, that is, an angle of the tip portion of approximately 90 degrees. The liquid 52 having such a conical shape is called a Taylor cone. When the electromagnetic attraction force is higher than the voltage at which the Taylor cone is formed, the tip of the Taylor cone extends toward the counter electrode 51 and finally becomes a droplet 53 charged with an excessive charge. When excessive charges are discharged by the separation of the droplet 53, the tip of the liquid pool 52a returns to a rounded shape. Thereafter, the tip of the liquid pool 52a forms a Taylor cone again, and the droplet 53 charged with an excessive charge is separated and released. Excess positive ions in the droplet 53 separated and ejected are repelled by the Coulomb force and gather on the surface of the droplet 53.

The droplet 53 has a small volume and is excessively charged. Therefore, a large force acts outward on the surface of the droplet 53. The droplet 53 is reduced in volume due to the evaporation of the solvent during the flight. As the volume of the droplet 53 decreases, the charge density increases and the outward force on the surface increases. When the limit called the Rayleigh limit is reached, the droplet 53 is split into a large number of fine droplets 53a. The fine droplet 53a generated by the division is also charged with an excessive charge. Therefore, when the solvent is vaporized, the Rayleigh right limit is reached again and re-split. By repeating such splitting, the droplet 53 finally generates gas phase ions and is sprayed on the counter electrode 51. The generation of gas phase ions by repeated splitting is due to Coulomb repulsion and is also called Coulomb explosion.

In order to cause such an electrospray phenomenon, a high voltage is applied between the capillary 50 and the counter electrode 51 to generate a strong electric field at the tip of the capillary 50, and an electromagnetic attraction force that overcomes the surface tension is accumulated in the liquid pool 52a. Need to occur. At this time, the necessary voltage is several thousand volts. For example, a liquid such as water requires a particularly high voltage because of its high surface tension. The applied voltage is preferably low because of the configuration of the power supply device 54. Further, when the voltage applied to the capillary 50 is high, corona discharge is generated near the tip of the capillary, and the formation of a stable Taylor cone is hindered.

Japanese Patent Application Laid-Open No. 2014-223591

In order to solve the above-mentioned problems of the prior art, the present invention can reduce the voltage applied to the discharge nozzle necessary for causing the electrospray phenomenon, and can generate corona discharge near the tip of the capillary. Electrospray that can be suppressed, and that the Taylor cone can be formed continuously and stably even when the surface tension of the liquid to be sprayed is large, and the liquid can be finely atomized and sprayed well. Discharge nozzle is provided.

The discharge nozzle for electrospray according to claim 1 of the present invention is a discharge nozzle for spraying a liquid by an electrospray ionization method, and includes a tubular member, a needle-like member, and a hydrophilic portion. The tubular member passes through the liquid to be sprayed. The needle-like member is attached to the center of the tubular member in a state of being electrically connected to the tubular member, and the tip portion projects from the discharge side end portion of the tubular member. A hydrophilic part is provided in the surface of the part which protrudes from the said discharge side edge part among the surface of the discharge side edge part of the said tubular member, and the said acicular member.

According to this configuration, the tip of the needle-like member protruding from the discharge side end of the tubular member has a large curvature and is closer to the counter electrode than the discharge side end of the tubular member. An electric field stronger than the discharge side end is formed. As a result, a stronger electric field is generated even when the applied voltage is the same as that of a conventional discharge nozzle having no needle-like member. Therefore, the voltage causing the electrospray phenomenon can be made lower than that of the conventional type, and the burden on the power source can be reduced. In addition, since the voltage applied to the discharge nozzle can be lowered, there is an effect that the occurrence of corona discharge near the tip of the discharge nozzle is also suppressed. Further, since the hydrophilic portion is provided on the surface of the discharge side end portion of the tubular member and the surface of the needle-like member protruding from the discharge side end portion, the surface tension of the liquid to be sprayed is high. In addition, the liquid is well adapted to the surface of the discharge side end portion of the tubular member and the surface of the portion of the needle-like member protruding from the discharge side end portion. Therefore, the Taylor cone can be formed continuously and stably at the tip of the discharge nozzle, and the liquid can be finely atomized and sprayed well.

Further, according to the discharge nozzle for electrospray according to claim 2, the angle of the tip of the needle-like member is set in the range of 20 degrees to 80 degrees. By setting the angle of the tip of the needle-like member in the range of 20 degrees to 80 degrees in this way, the contact area between the surface of the needle-like member and the liquid is increased, and the needle-like member is formed on the surface of the needle-like member. The liquid film can be thinned. Therefore, the electric charge easily moves from the needle-like member to the liquid, and the Taylor cone can be continuously formed in a more stable state at the tip of the discharge nozzle.

According to the discharge nozzle for electrospray according to claim 3, the tip of the needle-like member is rounded. By rounding the tip of the needle-like member in this way, a tip having no acute angle portion can be realized, and the tip of the needle-like member can be prevented from being exposed from the Taylor cone, that is, the liquid film. . Therefore, generation | occurrence | production of corona discharge can be suppressed and a Taylor cone can be continuously formed in the more stable state in the front-end | tip part of a discharge nozzle.

According to the discharge nozzle for electrospray according to claim 4, the electrospray discharge nozzle further includes an adjusting unit that adjusts the length of the needle-like member protruding from the discharge side end of the tubular member. According to this configuration, for example, by appropriately adjusting the protruding length of the needle-like member according to the magnitude of the surface tension of the liquid, a state in which a continuously stable Taylor cone is easily formed at the tip of the discharge nozzle is achieved. Can be realized.

Sectional drawing of the discharge nozzle for electrospray which concerns on one Embodiment Enlarged view showing the tip of the needle-shaped member Sectional view of the discharge nozzle showing the state before the electrospray phenomenon starts Cross section of the discharge nozzle showing the state after the electrospray phenomenon has begun The enlarged view which shows the front-end | tip part of the acicular member in the case of spraying the liquid with a large surface tension in the discharge nozzle which does not have a hydrophilic part Illustration of electrospray phenomenon

Hereinafter, an embodiment of an electrospray discharge nozzle will be described with reference to the drawings. A discharge nozzle 1 illustrated in FIG. 1 is an electrospray discharge nozzle that sprays a liquid by an electrospray ionization method, and includes a tubular member 2, a needle-like member 3, and a support block 4. The tubular member 2 is composed of a thin metal cylindrical tube, and a fixed side end portion 2 a which is one end portion is attached to the support block 4. The needle-like member 3 is a thin metal needle-like member formed with a sharp tip, and is inserted through the support block 4 into the center of the tubular member 2. The distal end portion of the needle-like member 3 protrudes from the opening of the discharge side end portion 2b that is the other end portion of the tubular member 2. The support block 4 is made of metal and supports the tubular member 2 and the needle-like member 3 in a state of being electrically connected. A flow path 5 through which the sample liquid L supplied to the tubular member 2 passes is formed inside the support block 4. The liquid L supplied from the flow path 5 into the tubular member 2 passes through a gap formed between the inner peripheral surface of the tubular member 2 and the outer peripheral surface of the needle-like member 3, and the discharge side end of the tubular member 2. It flows out from the part 2b. A DC high voltage is applied to the tubular member 2 and the needle-like member 3 from the power source 6 via the support block 4.

The discharge nozzle 1 further includes an adjustment unit 7. The adjustment part 7 adjusts the length of the needle-like member 3 protruding from the discharge side end part 2 b of the tubular member 2. The adjustment part 7 is comprised by the gear mechanism etc. which move the acicular member 3 along the longitudinal direction of the tubular member 2, for example. In this case, the maximum protrusion amount of the needle-like member 3 is set to a length approximately twice the diameter of the tubular member 2. On the other hand, the minimum protrusion amount of the needle-like member 3 is set at the same position as the discharge-side end portion 2b of the tubular member 2 at the tip end portion of the needle-like member 3, that is, “0” that does not protrude. The adjustment part 7 can change the protrusion amount of the front-end | tip part of the acicular member 3 between the maximum protrusion amount and the minimum protrusion amount. The maximum protrusion amount and the minimum protrusion amount of the needle-like member 3 can be appropriately changed and set according to the size and shape of the tubular member 2 and the needle-like member 3, the surface tension of the liquid to be sprayed, and the like.

As illustrated in FIG. 2, the angle α of the distal end portion of the needle-like member 3 is set to any angle in the range of 20 degrees to 80 degrees. In this case, it is preferable to set the angle α of the tip of the needle-like member 3 to approximately 40 degrees. Note that the angle α of the distal end portion of the needle-like member 3 can be defined as an angle formed by inclined lines L1 and L2 obtained by extending the inclined surface of the distal end portion. Moreover, the front-end | tip part of the acicular member 3 does not have an acute angle part, but is rounded. The degree of roundness of the distal end portion of the needle-like member 3, that is, the radius R of the distal end portion referred to as a so-called round is preferably set in a range of approximately 1/50 to 1/5 of the diameter of the needle-like member 3. For example, when the diameter of the needle-like member 3 is 1.5 mm, the radius of the tip portion may be set to about 0.1 mm.

When a liquid is sprayed by the electrospray ionization method using the discharge nozzle 1, a DC high voltage is applied from the power source 6 between the discharge nozzle 1 and the counter electrode 10. In this state, the liquid L is supplied into the tubular member 2 through the flow path 5 of the support block 4. Then, as illustrated in FIG. 3, the liquid L forms a liquid pool La at the distal end portion of the tubular member 2, that is, the discharge side end portion 2 b. Since a high voltage is applied between the tubular member 2 and the needle-like member 3 of the discharge nozzle 1, a high electric field is generated at the tip of the discharge nozzle 1. When the applied voltage to the discharge nozzle 1 is positive, the electric field is directed to the counter electrode 10. The positive ions present in the liquid pool La move to the surface of the liquid pool La on the counter electrode 10 side by this high electric field. On the contrary, the negative ions are directed toward the tubular member 2 and the needle-like member 3 side.

The negative ions that have reached the surface of the tubular member 2 and the surface of the needle-shaped member 3, both of which are made of metal, cause an oxidation reaction under a high electric field, give electrons to the tubular member 2 and the needle-shaped member 3, and are neutral. Turn into. For example, in the case of hydroxide ions, two water molecules, one oxygen molecule, and four electrons are generated by an oxidation reaction of four hydroxide ions. The four electrons move to the discharge nozzle 1 and move to the power source 6 and further to the counter electrode 10 via the wiring cable as the droplets charged with positive ions described later fly toward the counter electrode 10. Then, the positive charges carried to the counter electrode 10 are neutralized by droplets charged to positive ions.

A strong attraction force toward the counter electrode 10 is applied to the positive ions that have moved to the surface of the liquid pool La on the counter electrode 10 side by a strong electric field. Due to this strong suction force, the tip of the liquid pool La extends toward the counter electrode 10. On the other hand, surface tension acts on the liquid pool La, and the surface tension acts in a direction that prevents the tip of the liquid pool La from extending toward the counter electrode 10. When the two forces are balanced, as shown in FIG. 3, the liquid pool La forms a conical shape called a Taylor cone at its tip. When the applied voltage is higher than the voltage at which the Taylor cone is formed, the tip of the Taylor cone further extends toward the counter electrode 10. Finally, the liquid at the tip part is separated from the liquid pool La, and as shown in FIG. 4, it becomes fine droplets charged with positive ions and jumps out toward the counter electrode 10. It is the start of the electrospray phenomenon. When the charged droplets are ejected, the liquid pool La is reduced in the amount of charge, so that the suction force is weakened and the tip is rounded. Thereafter, a Taylor cone is formed again, and a droplet charged with positive ions is discharged toward the counter electrode 10 again. By repeating such an operation, the charged fine droplets are continuously and stably sprayed.

The discharge nozzle 1 includes a metal needle-like member 3 at the center of a metal tubular member 2, and the tip of the needle-like member 3 has a pointed shape. It protrudes from the opening of the part 2b. When a positive potential is applied to the discharge nozzle 1, the surface of the metal portion of the discharge nozzle 1 is positively charged and generates an electric field toward the counter electrode 10. The electric field on the surface of the metal portion becomes stronger as the sharp portion has a larger curvature and the portion closer to the counter electrode 10 having a negative potential. Therefore, in a conventional discharge nozzle that does not include a needle-like member at the center of the tubular member, a strong electric field is intensively generated at the cylindrical end of the discharge side end portion of the tubular member.

On the other hand, in the discharge nozzle 1 of the present embodiment, a strong electric field is generated at the tip of the needle-like member 3 in addition to the cylindrical end of the discharge-side end 2b of the tubular member 2. The tip of the needle-like member 3 has a generally pointed shape as a whole, and is closer to the counter electrode 10 than the discharge-side end 2 b of the tubular member 2. Therefore, an electric field stronger than the cylindrical end of the discharge side end 2 b of the tubular member 2 is formed at the tip of the needle-like member 3. Therefore, the positive ions in the liquid pool La tend to concentrate on the tip of the needle-like member 3 where a stronger electric field is generated. That is, according to the discharge nozzle 1 of the present embodiment having the needle-like member 3, compared to the discharge nozzle having no conventional needle-like member, a strong electric field is applied to the tip of the needle-like member 3 even when the applied voltage is the same. appear.

Therefore, according to the discharge nozzle 1 according to the present embodiment, an electrospray phenomenon can be caused by a voltage lower than that of a conventional discharge nozzle that does not include a needle-like member. If the voltage applied to the discharge nozzle 1 can be lowered, the burden on the power source 6 is reduced. Moreover, if the voltage applied to the discharge nozzle 1 can be lowered, the occurrence of corona discharge near the tip of the discharge nozzle 1 can be suppressed. Thus, according to the discharge nozzle 1 having the needle-like member 3 of the present embodiment, the voltage causing the electrospray phenomenon can be made lower than that of the conventional type, and the occurrence of corona discharge can be suppressed.

By the way, according to the discharge nozzle 1 which concerns on this embodiment, when the liquid L passes the narrow clearance gap between the internal peripheral surface of the tubular member 2, and the outer peripheral surface of the needle-shaped member 3, it is the needle-shaped member 3's. Contact the surface. Then, the liquid L that has reached the discharge side end portion 2 b of the tubular member 2 further flows while contacting the surface of the tip portion of the needle-like member 3. At this time, if a high voltage is applied to the needle-like member 3, a Taylor cone is formed at the tip of the needle-like member 3 to cause an electrospray phenomenon, and the liquid L becomes a charged droplet and becomes a counter electrode. Jump out toward the 10th.

That is, according to the discharge nozzle 1 according to the present embodiment, the liquid L contacts the surface of the tip of the needle-like member 3 to which a high voltage is applied before being sprayed as droplets. An electrochemical reaction occurs on the surface of the needle-like member 3. That is, when the applied voltage is positive, the negative ions in the liquid are neutralized by supplying electrons to the needle-like member 3. The neutral molecule separates positive ions and negative ions and gives negative ions to the needle-like member 3. The positive ions go to the tip of the Taylor cone. The amount of electrochemical reaction generated is determined by the contact area between the liquid L and the needle-like member 3, and the larger the amount of electrochemical reaction generated, the more positive droplets can be retained and sprayed. . Therefore, it is preferable to bring the liquid L into contact with the surface of the needle-like member 3 over a wider area.

However, as illustrated in FIG. 5, when the surface tension of the liquid L is large, the liquid L is not easily adapted to the surface of the needle-like member 3 and is repelled. That is, the adhesion between the liquid L and the surface of the needle-like member 3 is deteriorated, and a sufficient contact area between the liquid L and the surface of the needle-like member 3 cannot be ensured. For this reason, it becomes difficult to form a continuously stable Taylor cone, and it becomes difficult to finely atomize and spray the liquid L satisfactorily.

Therefore, as illustrated in FIG. 1, the discharge nozzle 1 according to the present embodiment is formed on the surface of the discharge side end 2 b of the tubular member 2 and the surface of the portion of the needle-like member 3 protruding from the discharge side end 2 b. The hydrophilic part 8 which exhibits hydrophilicity is provided. In this case, the hydrophilic portion 8 of the tubular member 2 is integrally provided as a part of the tubular member 2 by performing a plasma irradiation process on the surface of the discharge side end portion 2b of the tubular member 2. Further, the hydrophilic portion 8 of the needle-like member 3 is integrally provided as a part of the needle-like member 3 by performing a plasma irradiation process on the surface of the tip portion of the needle-like member 3. By performing plasma treatment on the surface of the metal member, a cleaning effect on the surface can be obtained, and hydrophilicity is improved. The hydrophilic portion 8 is considered to be formed by such a cleaning effect by the plasma irradiation treatment. In the present embodiment, it is preferable to provide at least the hydrophilic portion 8 having a water contact angle of 10 degrees or less.

The hydrophilic portion 8 of the tubular member 2 is preferably provided at least on the cylindrical end and the outer peripheral surface of the discharge side end portion 2b of the tubular member 2. That is, the liquid L flowing out between the tubular member 2 and the needle-shaped member 3 first forms a substantially spherical liquid mass including the outer peripheral surface of the discharge side end 2b at the discharge side end 2b of the tubular member 2. Then, a liquid pool La extending toward the counter electrode 10 is formed. Therefore, by providing the hydrophilic portion 8 at the cylindrical end and the outer peripheral surface of the discharge side end portion 2b of the tubular member 2 in contact with the liquid L in the initial stage before the liquid pool La is formed, the liquid pool La is formed. From the initial stage before formation, the contact area between the liquid L and the metal portion of the discharge nozzle 1, that is, the tubular member 2 can be increased.

Further, the hydrophilic portion 8 of the needle-like member 3 is provided at least in a region including the surface of the portion protruding from the discharge side end portion 2b of the tubular member 2 in a state where the needle-like member 3 protrudes to the maximum protruding amount. preferable. That is, the discharge nozzle 1 according to the present embodiment has a configuration in which the protruding amount of the needle-like member 3 can be adjusted. Therefore, by providing the hydrophilic portion 8 in a region including the surface of the portion protruding from the discharge side end portion 2b of the tubular member 2 with the needle-like member 3 protruding to the maximum protruding amount, the needle-like member 3 Regardless of the amount of protrusion, the contact area between the liquid L and the surface of the tip of the needle-like member 3 protruding from the discharge-side end 2b of the tubular member 2 can be ensured to the maximum extent.

According to the discharge nozzle 1 of the present embodiment in which the liquid L is brought into contact with the needle-like member 3 over a wider area, the amount of electrochemical reaction that occurs before the liquid L reaches the Taylor cone at the tip increases. For this reason, the amount of positive ions per unit flow rate of the liquid L reaching the Taylor cone at the tip is much larger than that of a conventional discharge nozzle having no needle-like member when the flow rate is the same. In addition, the amount of positive ions per unit flow rate of the liquid L that has reached the Taylor cone at the tip is much larger than that of a discharge nozzle that does not have a hydrophilic portion if the flow rate is the same. It is considered that the amount of positive ions carried away by one droplet that jumps out from the tip of the Taylor cone is almost constant. Therefore, according to the discharge nozzle 1 of the present embodiment, it is possible to discharge a larger amount of sufficiently charged droplets.

According to the discharge nozzle 1 according to the present embodiment, the hydrophilic portion 8 is provided on the surface of the discharge side end 2b of the tubular member 2 and the surface of the needle-like member 3 that protrudes from the discharge side end 2b. Yes. According to this configuration, even when the surface tension of the liquid L to be sprayed is large, the liquid L protrudes from the discharge side end 2 b of the surface of the discharge side end 2 b of the tubular member 2 and the needle-like member 3. Become familiar with the surface of the part to be. Therefore, the Taylor cone can be formed continuously and stably at the tip of the discharge nozzle 1, and the liquid L can be finely atomized and sprayed well.

Further, according to the discharge nozzle 1, the angle α of the tip of the needle-like member 3 is set in the range of 20 degrees to 80 degrees. According to this configuration, the liquid film formed on the surface of the needle-like member 3 can be made thin while increasing the contact area between the surface of the needle-like member 3 and the liquid L. Therefore, the electric charge easily moves from the needle-like member 3 to the liquid L, and the Taylor cone can be continuously formed at the tip of the discharge nozzle 1 in a more stable state. In addition, the inclined lines L1 and L2 that define the angle α of the distal end portion of the needle-like member 3 may not be a straight line, and may be, for example, a gently curved curve. That is, the tip portion of the needle-like member 3 may have a slightly curved surface instead of a sharp pointed shape.

Also, according to the discharge nozzle 1, the tip of the needle-like member 3 is rounded. According to this configuration, it is possible to realize the tip of the needle-like member 3 that does not have an acute angle portion, and it is possible to avoid the tip of the needle-like member 3 from being exposed from the Taylor cone, that is, the liquid film. Therefore, generation | occurrence | production of corona discharge can be suppressed and a Taylor cone can be continuously formed in the more stable state in the front-end | tip part of the discharge nozzle 1. FIG.

Further, according to the discharge nozzle 1, the length of the needle-like member 3 protruding from the discharge side end 2 b of the tubular member 2 can be adjusted by the adjusting portion 7. According to this configuration, for example, by appropriately adjusting the protruding length of the needle-like member 3 according to the surface tension of the liquid L, a continuously stable Taylor cone is formed at the tip of the discharge nozzle 1. Easy state can be realized.

Note that the present invention is not limited to the above-described embodiment, and can be expanded or changed as follows, for example. For example, the tubular member 2 may be made of a nonconductive material such as glass instead of metal. By configuring the tubular member 2 with a non-conductive material, the occurrence of corona discharge near the tip of the tubular member 2 can be further suppressed.

Further, the method of forming the hydrophilic portion 8 is not limited to the plasma irradiation treatment, and may be a hydrothermal treatment or an ultraviolet irradiation treatment, for example. That is, various techniques can be adopted as long as an element that exhibits hydrophilicity can be formed on the surface of a metal member. Further, the hydrophilic portion 8 is not formed by the above-described treatment, for example, and may be configured by coating the surface of a metal member with a hydrophilic material. Moreover, the base material which comprises the hydrophilic part 8 is not restricted to a metal member, For example, by plating the surface of a resin component and performing various hydrophilic treatments on the surface The hydrophilic portion 8 may be configured.

Claims (4)

An electrospray discharge nozzle for spraying a liquid by electrospray ionization,
A tubular member through which liquid passes;
A needle-like member attached to the center of the tubular member in a state of being electrically connected to the tubular member, and having a tip protruding from a discharge side end of the tubular member;
A hydrophilic portion provided on the surface of the discharge side end of the tubular member and the surface of the needle-like member protruding from the discharge side end; and
A discharge nozzle for electrospray. The discharge nozzle for electrospray according to claim 1, wherein the angle of the tip of the needle-like member is 20 to 80 degrees. The discharge nozzle for electrospray according to claim 1 or 2, wherein the tip of the needle-like member is rounded. The discharge nozzle for electrospray according to any one of claims 1 to 3, further comprising an adjustment unit that adjusts a length of the needle-like member protruding from the discharge side end.

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