JPH09292367A - Mass spectrometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable stable analysis of a thermally unstable components and to improve safety by providing an exhaust port for exhausting solvent molecules in the vicinity of an needle electrode, and preventing the dew condensation of the solvent at the needle electrode. SOLUTION: A metal cover 17 is provided for holding a needle electrode 9 from a safety standpoint, so as to avoid making direct contact with the needle electrode 9, on which a high voltage is applied. Here, an exhaust port 20 for exhausting solvent molecules is provided at the position close to the needle electrode 9 of the metal cover 17. Since a part of the solvent molecules is discharged to the outside of the metal cover 17 from the exhaust port 20, the partial pressure of the solvent molecules in the metal cover is decreased, and the dew condensation of the solvent molecules at the needle electrode 9 can be prevented. Furthermore, an evacuating means, such as fan, can be provided at the exhaust port 20 for increasing the exhausting efficiency of the solvent molecules.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mass spectrometer for analyzing a sample in a solution, and more particularly to an apparatus combining a liquid phase separation means such as a liquid chromatograph with a mass spectrometer.

[0002]

2. Description of the Related Art At present, in the field of analysis, development of mass spectrometry for a sample in a solution is regarded as important. This is because many biological substances and environment-related substances exist as solutions. In particular, in order to analyze a mixture, an apparatus in which a liquid phase separation means such as a liquid chromatograph and a mass spectrometer are directly connected is required.

According to FIG. 4, Analytical Chemistry, Volume 60, p.774, 1988 (Analytical Che
The conventional liquid chromatograph / mass spectrometer described in mistry, 60, 774 (1988) will be described. The sample solution sent from the liquid chromatograph 1 is introduced into the atomizing section 4 via the pipe 2 and the connector 3. The atomizing section 4 is composed of a metal tube 5 and a heated metal block 6a. The sample solution introduced into the metal tube 5 is heated and sprayed by the heat from the metal block 6a. The droplets generated by the atomization are sent to a vaporization section 8 constituted by a heated metal block 6b having an opening 7. The droplet is heated and vaporized while passing through the opening 7. Gaseous sample molecules obtained by vaporizing the droplets are introduced into the ionization section 10 in which the needle electrode 9 is arranged. The needle electrode 9 is held on the metal cover 17 by the insulator 19. A high voltage of several kilovolts is applied to the needle electrode 9 by the high voltage power source 18 to cause the ionization section 10 to generate corona discharge. The sample molecules react with the ions generated by the corona discharge and are ionized. Ions relating to the sample generated in such a process are exhausted through the ion intake pore 11a, the differential exhaust unit 13 exhausted by the exhaust system 12a, and the ion intake pore 11b.
It is taken in by the vacuum unit 14 evacuated by b, and the vacuum unit 1
Mass analysis is carried out by the mass spectrometric section 15 installed at No. 4.
The mass analyzed ions are detected by the detector 16, and the detected signal is processed by the data processing device.

[0004]

The above-mentioned prior art has the following problems. When the sample to be analyzed is a thermally unstable compound, in order to prevent thermal decomposition of the sample, the temperature of the metal block forming the atomizing part and the vaporizing part must be lowered. Under such conditions, the droplets generated by spraying cannot be sufficiently vaporized, and therefore, the solution (mainly the solvent) may be condensed on the needle electrode during long-term analysis. If dew condensation occurs on the needle electrode, the discharge becomes unstable, making stable measurement difficult, and for safety reasons, such as a short circuit between the needle electrode and the metal cover holding the needle electrode, causing an overcurrent. There was a problem. An object of the present invention is to prevent dew condensation on the needle electrode. By preventing condensation on the needle electrode, stable measurement can be realized and safety is improved.

[0005]

In the present invention, a means for supplying a sample solution consisting of a solvent and a solute, an ionizing means for ionizing the sample solution, and a mass of ions generated by the ionizing means are analyzed. A mass spectrometer comprising means, having a needle electrode for generating a corona discharge, and a holding member for holding the needle electrode, wherein the solvent of the solvent is provided in the vicinity of the holding portion of the needle electrode of the holding member. The above problem is solved by providing an opening for discharging molecules. A mass spectrometer comprising means for supplying a sample solution consisting of a solvent and a solute, ionization means for ionizing the sample solution, and means for analyzing the mass of ions produced by the ionization means, The above problem can be similarly solved by providing a needle electrode for generating a corona discharge and a heater for heating the needle electrode.

[0006]

FIG. 1 shows a first embodiment of the present invention.
This will be described below. The sample solution sent from the liquid chromatograph 1 is introduced into the atomizing section via the pipe 2 and the connector 3. The sample solution is heated and atomized by the atomizing unit 4.
The liquid droplets generated by the spraying are sent to the vaporization unit 8 and vaporized. Gaseous sample molecules obtained by vaporizing the droplets are introduced into the ionization section 10 in which the needle electrode 9 is arranged. A high voltage of several kilovolts is applied to the needle electrode 9 to generate corona discharge in the ionization part. The sample molecules react with the ions generated by the corona discharge and are ionized. Ions relating to the sample generated in such a process are taken into the vacuum unit 14 through the ion intake pores 11a and 11b and the differential evacuation unit 13, and are subjected to mass analysis by the mass analysis unit 15 installed in the vacuum unit 14. To be done. The mass spectrometric section 15 includes
Although there are various types such as a magnetic field type, a quadrupole type, and an ion trap type, the present invention is effective regardless of the type of the mass spectrometric section. The mass-analyzed ions are detected by the detector 16,
The detected signal is processed by the data processing device.

The metal cover 17 is provided for holding the needle electrode and from the viewpoint of safety so that the needle electrode to which a high voltage is applied cannot be directly touched. Here, a discharge port 20 for discharging solvent molecules is provided at a position near the needle electrode of the metal cover 17. Since part of the solvent molecules are discharged from the discharge port 20 to the outside of the metal cover 17, the metal cover 17
The partial pressure of the solvent molecules inside is reduced, and the condensation of the solvent molecules on the needle electrode 9 can be prevented. In order to increase the efficiency of solvent molecule discharge, the discharge port 20 may be provided with an exhaust means 21 such as a fan, as shown in FIG. Also, as shown in FIG.
As shown in FIG. 3, by feeding a gas such as dry nitrogen into the metal cover 17 through the air supply port 22, the metal cover 1
It is possible to reduce the partial pressure of the solvent molecules in 7 and prevent dew condensation on the needle electrode 9. Further, if gas from the air supply port 22 is blown to the needle electrode 9, the partial pressure of the solvent molecules around the needle electrode 9 is reduced,
Condensation on the needle electrode 9 can be prevented.

A second embodiment of the present invention will be described with reference to FIG. In order to prevent the condensation of the solvent on the needle electrode, the temperature of the needle electrode may be kept higher than the boiling point of the solvent.
In FIG. 2, the heater 24 is attached to the needle electrode 9,
By heating the needle electrode 9 with heat from 4, the temperature of the needle electrode 9 is kept higher than the boiling point of the solvent.

Since a high voltage of several kilovolts is applied to the needle electrode, when it is difficult to directly attach the heater to the needle electrode, the heater is arranged near the needle electrode.
The needle electrode may be heated by radiant heat from the heater. Further, the needle electrode may be heated by an indirect method, for example, by attaching a heater to the metal cover to heat the metal cover and heating the needle electrode with radiant heat from the metal cover.

A third embodiment of the present invention will be described with reference to FIG. Condensation on the needle electrode becomes remarkable when the jet of the solution generated in the atomizing unit is blown onto the needle electrode. This is because the solution jet contains a large number of solvent molecules and the jet electrode hits the needle electrode to cool the needle electrode. Therefore, as shown in FIG. 3, dew condensation on the needle electrode 9 can be prevented by providing the needle electrode cover 27 for preventing the jet 26 from being sprayed on the needle electrode 9. The shape of the needle electrode cover 27 is not limited to the cylindrical shape including the needle electrode 9 as shown in FIG. For example,
The plate-shaped shield plate may be arranged upstream of the needle electrode (that is, between the atomizing portion and the needle electrode). However, the needle electrode 9
In order to generate a corona discharge by applying a high voltage to the
As shown in FIG. 5, it is desirable that there is no shield plate (needle electrode cover) between the tip of the needle electrode 9 and the electrode where the ion-incorporating pore 11a is opened, which obstructs discharge.

By the method described with reference to FIGS. 1, 2, and 3, it is possible to prevent the dew condensation of the solvent on the needle electrode. Therefore, when analyzing a thermally unstable substance, even if the temperature of the metal block forming the atomizing part and the vaporizing part is lowered, the discharge can be stably maintained, and stable measurement can be performed.
Further, it is possible to avoid a safety problem such as a short circuit between the needle electrode and the metal cover holding the needle electrode due to dew condensation and an overcurrent flows.

[0012]

According to the present invention, dew condensation on the needle electrode can be prevented. Therefore, it is possible to perform stable analysis for a long time even when the temperature of the atomizing section or the vaporizing section is lowered, and the safety is improved because a short circuit due to dew does not occur.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the configuration of a liquid chromatograph / mass spectrometer having a discharge port for discharging solvent molecules in the vicinity of a needle electrode, which is a first embodiment of the present invention.

FIG. 2 is a sectional view showing a configuration of a liquid chromatograph / mass spectrometer for heating a needle electrode, which is a second embodiment of the present invention.

FIG. 3 is a diagram showing a mass spectrometer in which a needle electrode is provided with a cover, which is a third embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a configuration of a conventional liquid chromatograph / mass spectrometer.

[Explanation of symbols]

1 ... Liquid chromatograph, 2 ... Piping, 3 ... Connector, 4
... Atomizing section, 5 ... Metal tube, 6a, 6b ... Metal block, 7
... Opening part, 8 ... Vaporizing part, 9 ... Needle electrode, 10 ... Ionizing part, 11a, 11b ... Ion uptake pores, 12a, 1
2b ... Exhaust system, 13 ... Differential exhaust, 14 ... Vacuum section, 15 ...
Mass spectrometric section, 16 ... Ion detector, 17 ... Metal cover,
18 ... High-voltage power supply, 19 ... Insulator, 20 ... Discharge port, 21 ...
Exhaust means, 22 ... Air supply port, 23 ... Air supply means, 24 ... Heater, 25 ... Heater power supply, 26 ... Jet, 27 ... Needle electrode cover.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yukiko Hirabayashi 1-280 Higashi Koigakubo, Kokubunji, Tokyo Metropolitan Research Laboratory, Hitachi, Ltd. (72) Hideaki Koizumi 1-280 Higashi Koikeku, Kokubunji, Tokyo Hitachi Ltd. Central Research Center

Claims (6)

[Claims] 1. A mass spectrometer comprising: a means for supplying a sample solution consisting of a solvent and a solute; an ionization means for ionizing the sample solution; and a means for analyzing the mass of ions produced by the ionization means. And a needle electrode for generating a corona discharge, and a holding member for holding the needle electrode, and an opening for discharging molecules of the solvent in the vicinity of the holding portion of the needle electrode of the holding member. A mass spectrometer comprising: 2. A mass spectrometer comprising: a means for supplying a sample solution consisting of a solvent and a solute; an ionization means for ionizing the sample solution; and a means for analyzing the mass of the ions produced by the ionization means. A mass spectrometer comprising a needle electrode for generating a corona discharge and a heater for heating the needle electrode. 3. The mass spectrometer according to claim 2, wherein the temperature of the needle electrode is higher than the boiling point of the solvent. 4. A mass spectrometer comprising: a means for supplying a sample solution comprising a solvent and a solute; an ionization means for ionizing the sample solution; and a means for analyzing the mass of the ions generated by the ionization means. A mass spectrometer having a needle electrode for generating a corona discharge, the temperature of the needle electrode being maintained at a temperature higher than the boiling point of the solvent. 5. A means for supplying a sample solution consisting of a solvent and a solute, an atomizing means for atomizing the sample solution, an ionizing means for ionizing the sample solution, and an ion generated by the ionizing means. A mass spectrometer comprising a means for analyzing mass, comprising: a needle electrode for generating a corona discharge; and a jet electrode for preventing the jet of the sample solution generated by the atomizing means from being sprayed on the needle electrode. A mass spectrometer having a shielding member. 6. The mass spectrometer according to claim 5, wherein the shielding member is an insulator including the needle electrode.