JPH0413962A - Electrospray type mass spectrograph - Google Patents

Abstract

PURPOSE:To introduce a sample ionized efficiently into a mas spectrograph by arranging a conductor on which an orifice is formed to make fine liquid drops charged pass at the center of a truncated cone shaped conductor provided between a jet port of a capillary tube for transferring a liquid sample and a diaphragm electrode. CONSTITUTION:Electric field is concentrated on an orifice 2c provided at the center of truncated cone-shaped conductors 2 and 3. Liquid drops charged electrically which are jetted at a jet port of a capillary tube 1 for transferring a liquid sample are introduced into the orifice 2c of the conductors 2 and 3 without diverging. The liquid drops passing through the orifice 2c of the conductors 2 and 3 travel straight without being attracted to internal walls of the conductors 2 and 3. The liquid drops undergoes the removal of its desolven by an inert gas supplied between a diaphragm electrode 11 and skimmer electrodes 4 and 5 while being dried and ions to be measured alone are introduced into a mass spectrograph 15 thereby enabling the introducing of the sample ionized efficiently into a mass spectrograph 15.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an electrospray mass spectrometer that performs mass spectrometry by ionizing a sample in a solution, particularly a component in an eluate of liquid chromatography, by an electrospray method. It is something.

(Prior Art) In recent years, research and development has been underway to ionize samples separated by liquid chromatography and directly introduce them into a mass spectrometer.

In other words, the method of generating fine electrically charged droplets, drying these droplets to extract ions into the gas phase, and detecting this is applicable to thermospray, atmospheric pressure spray (API), electrospray, etc. has been done. Among these methods, the electrospray method can generate charged droplets most efficiently, so it is recommended as a method for introducing liquid samples, especially eluates from liquid chromatography, into a mass spectrometer for analysis. Attention has been paid.

The operating principle of the electrospray method is as follows.

The sample to be ionized is dissolved in a solvent, preferably a polar solvent, and the resulting solution is slowly moved through a liquid sample transfer capillary tube that is subjected to a high potential. When this solution is then jetted at the exit of the liquid sample transfer capillary tube, the solution breaks down into small droplets and the solvent begins to evaporate, while the droplets are simultaneously electrically charged by a strong electric field. The electrically charged droplets thus produced are further enhanced by a high potential diaphragm electrode and a skimmer electrode having orifices through which they pass electrically charged. The enhanced ions are desolvated and dried by an inert gas blown out from the gap between the diaphragm electrode and the skimmer electrode, and only the ions are guided to the mass spectrometer.

(Problem to be solved by the invention) In the conventional electrospray mass spectrometer,
The generated ions were introduced into the mass spectrometer through a flat diaphragm electrode and an orifice in a skimmer electrode, which is part of the vacuum section.

FIG. 2 is a simplified cross-sectional view of such a conventional electrospray mass spectrometer.

As shown in FIG. 2, a conventional electrospray mass spectrometer generally consists of a liquid sample transfer capillary 3
1, a flat diaphragm electrode 32, and a skimmer electrode 33. A potential having the same polarity as the sample to be ionized is applied to the liquid sample transfer capillary tube 31, the diaphragm electrode #132, and the skimmer electrode [33], respectively.

In this case, the droplets ejected from the liquid sample transfer capillary tube 31 are electrically charged and sprayed toward the diaphragm electric fi32. However, each droplet is moved to the diaphragm electrode 32 due to radial electric lines of force with the liquid sample transfer capillary tube 31 at its apex and Coulomb repulsion between ions.
As it approaches, it diverges in a trumpet shape. Therefore, such an apparatus has the drawback that the directionality of ions to be analyzed is poor and the number of ions introduced into the mass spectrometer is reduced.

FIG. 3 is a simplified cross-sectional view of a conventional device that is an improved version of the device shown in FIG. A conical conductor 34 is provided between the liquid sample transfer capillary 31 and the flat diaphragm electrode 32 . In this conventional device, the electric field is concentrated at an orifice 34a provided in the center of the conductor 34.

Therefore, the ionized droplets can be guided into the orifice 34a of the conductor 34 without being dispersed.

However, in this conventional device, most of the ions that have passed through the orifice 34a of the conductor 34 are attracted to the inner wall surface of the conical conductor 34, collide with the inner wall surface, cause discharge, and disappear. Therefore, most of the ions reach the target diaphragm electrode 32, and as a result, the number of ions introduced into the mass spectrometer is also extremely small.

It is an object of the present invention to provide an electrospray mass spectrometer that can solve the problems of the conventional devices described above and efficiently introduce ions generated by electrospray into a mass spectrometer. be.

(Means for Solving the Problems) The present invention provides a liquid sample transfer capillary to which a high potential is applied, which has a jet nozzle at one end that jets a solution obtained by dissolving a sample to be ionized in a solvent; a diaphragm electrode having an orifice for passing electrically charged fine droplets ejected from a transfer capillary, a skimmer electrode having an orifice for passing droplets enhanced by the diaphragm electrode, and between the diaphragm electrode and the skimmer electrode. an inert gas supply means for supplying an inert gas to desolvent the droplets and dry them to leave only the ions to be measured;
In an electrospray mass spectrometer that analyzes a sample in a solution by ionizing it with electrospray, it is equipped with a mass spectrometer that accepts ions that have passed through the orifice of the skimmer electrode and performs mass spectrometry. One or more truncated conical conductors provided between the injection port and the diaphragm electrode, with an orifice through which fine electrically charged droplets are passed approximately in the center of the flat part. It is characterized by having a conductor in which is formed.

(Function) Also in the present invention, the electric field is concentrated at the orifice provided at the center of the truncated conical conductor. Therefore, the electrically charged droplets ejected from the injection port of the liquid sample transfer capillary tube are guided into the orifice of the truncated conical conductor without divergence. A droplet that does not pass through the orifice of the conductor travels straight without being attracted to the inner wall surface of the truncated conical conductor.

The droplets are desolvated and dried by an inert gas supplied between the diaphragm electrode and the skimmer electrode, and only the ions to be measured are introduced into the mass spectrometer.

(Example) Hereinafter, the electrospray mass spectrometer of the present invention will be described in detail using the drawings.

FIG. 1 is a sectional view of an embodiment of an electrospray mass spectrometer according to the present invention.

The electrospray mass spectrometer of the present invention is generally configured to include an electrospray chamber 21, a vacuum chamber 16, and a vacuum chamber 17.

In the electrospray chamber 21, about 0.1
A liquid sample transfer capillary tube 1 having an injection port of mm, a pair of truncated conical conductors 2.3, and a diaphragm electrode 11,
They are arranged so as to be insulated from each other by an insulating material.

The conductor 2 is composed of a disk-shaped flat part 2a and a flared part 2b that spreads from the flat part 2a.
An orifice 2c with a circular cross section is formed in the center of a. In the preferred embodiment shown, the flats have a diameter of about 8 mm and the orifice has a diameter of about 1 mm. The conductor 3 has the same structure as the conductor 2, and is composed of a flat portion 3a in which an orifice 3c is formed and a flared portion 3b extending from the flat portion 3a.

The flat diaphragm electrode also has an orifice of circular cross section formed in its center.

At the boundary between the electrospray chamber 21 and the vacuum chamber 16,
A truncated cone-shaped skimmer electric 'J#14 with a 100 μm orifice 4a in the center is installed, and a 1°5 mm orifice 5 in the center is installed at the boundary between the vacuum chamber 16 and the vacuum chamber 17.
A skimmer electric tif15 having a truncated cone shape is installed. The vacuum chamber 16 is depressurized to 10 Torr by a vacuum pump, while the vacuum chamber 17 is depressurized to 10 Torr by a vacuum pump.
The pressure is reduced to 0 torr.

An inert gas flows between the diaphragm electrode 11 and the skimmer electrode 4.
The gas is introduced from the gas inlet 18 provided between the two, and passes through the orifice lla of the diaphragm electrode 11, the orifice 3c of the conductor 3, and the orifice 2c of the conductor 2 to the gas outlet 1.
It is discharged from one.

Also installed in the vacuum chamber 17 is a quadrupole mass spectrometer 15 with lens elements 12, 13, 14 for focusing the ions. This quadrupole mass spectrometer 15 is adjusted to be located at a distance of 2 to 30+ nm from the inside of the skimmer electrode 5.

The liquid sample transfer capillary 1, the conductor 2, the conductor 3, the diaphragm electrode 11, and the skimmer electrode 4 are connected to the same polarity as the sample to be ionized, respectively.
Potentials of 0kV, 200V and 50V are applied.

When a potential is applied to the conductors 2.3, the electric field is concentrated at the orifice 2C13c provided in the center of each conductor.6 Therefore, the electrically charged liquid ejected from the injection port of the liquid sample transfer capillary 1 The droplet does not diverge and travels straight through the orifice 2c of the truncated cone-shaped conductor 2, and is further guided into the orifice 3C of the truncated cone-shaped conductor 3. The droplet passing through the orifice '3c of the conductor 3 travels straight without being attracted to the inner wall surface of the truncated cone-shaped conductor 3.
It is guided into the orifice 2c of the diaphragm electrode 11.

The droplets are desolvated and dried by an inert gas supplied between the diaphragm electrode 11 and the skimmer electrode 4, and only the ions to be measured are introduced into the mass spectrometer 15.

In the illustrated embodiment, two truncated conical conductors are installed, but the number of conductors may be one, or three or more.

In ionization using the electrospray method, it was generally believed that there were limits to the flow rate and composition of the solvent. That is,
In the case of a simple electrospray mass spectrometer as shown in Figures 2 and 3, the flow rate is preferably in the range of 2 to 50 μI/min, and the salt concentration of the solvent should be no less than 10-4 molar for good spraying. , ionization could not occur.

However, in the case of the electrospray mass spectrometer of the present invention as shown in FIG. 1, it was possible to widen the range in which good electrospray atomization and ionization can be performed. Flow rates could be approximately up to twice as fast as in conventional devices, and thus could range from 2 to 100 μI/min. Furthermore, it has become possible to spray and ionize salt to a concentration 10 times higher than with existing methods.

(Effects of the Invention) The electrospray mass spectrometer of the present invention includes one or more truncated conical conductors installed between the injection port of the liquid sample transfer capillary tube and the diaphragm electrode, By having a conductor with an orifice formed in the center of its flat part to allow electrically charged fine droplets to pass through, samples ionized by electrospray can be efficiently introduced into the mass spectrometer. Not only is it now possible to do this, but it also has the effect of greatly easing restrictions on flow rate, solvent composition, etc. compared to conventional devices.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of an electrospray mass spectrometer according to the present invention. FIG. 2 is a simplified cross-sectional view of a conventional electrospray mass spectrometer. FIG. 3 is a simplified cross-sectional view of a conventional device that is an improvement on the device shown in FIG. 1... Liquid sample transfer capillary 2.3... Conductor 4.5... Skimmer electrode 11... Diaphragm electrode 12.13.14... Lens element 15... Mass spectrometer 16.17 ...Vacuum chamber 18...Gas inlet 9...Gas outlet...Electrospray chamber

Claims (1)

[Scope of Claims] A liquid sample transfer capillary to which a high potential is applied and which has an injection port at one end for jetting out a solution obtained by dissolving a sample to be ionized in a solvent; a diaphragm electrode having an orifice through which fine electrically charged droplets pass; a skimmer electrode having an orifice through which the droplets enhanced by the diaphragm electrode; and an inert gas between the diaphragm electrode and the skimmer electrode. an inert gas supply means that desolvents and dries the droplets to produce only the ions to be measured; and a mass spectrometer that receives the ions that have passed through the orifice of the skimmer electrode and performs mass spectrometry. In a mass spectrometer that analyzes a sample in a solution by ionizing it with electrospray, the mass spectrometer is equipped with one or more truncated conical shapes provided between the injection port of the liquid sample transfer capillary and the diaphragm electrode. An electrospray mass spectrometer characterized in that the conductor has an orifice formed substantially in the center of a flat part thereof through which fine electrically charged droplets pass. (2) The electrospray mass spectrometer according to claim 1, wherein the flat portion of the conductor has a disk shape with a diameter of about 8 mm;
An electrospray mass spectrometer characterized in that the orifice of the flat portion has a circular cross section with a diameter of about 1 mm. (3) The electrospray mass spectrometer according to claim 1, wherein two of the conductors are provided between the injection port of the liquid sample transfer capillary tube and the diaphragm electrode. Mass spectrometer. (4) In the electrospray mass spectrometer according to claim 3, the liquid sample transfer capillary, a conductor closer to the liquid sample transfer capillary, a conductor closer to the diaphragm electrode, the diaphragm electrode, and the The skimmer electrodes were heated at 3 to 4 kV, 1. with the same polarity as the sample to be ionized, respectively.
An electrospray mass spectrometer characterized in that potentials of 5kV, 1.0kV, 200V and 50V are applied.