JPH1069876A - Filament for specimen directly introducing probe for mass spectrograph - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily sample a specimen, and stably retain it on a filament, provided on the tin of the specimen directly introducing probe of a separation type electron impact ionization mass spectrograph; and also to eliminate an effect by a thermoelectron from an ion source filament in resistantly heating and gasifying the specimen by the filament. SOLUTION: In a filament 1, provided on the tip of a specimen directly introducing prove for directly introducing a specimen to a separation type electron impact ionization mass spectrograph, wherein the ionization of the specimen in mass spectrometry is made by a thermoelectron from an ion source filament, and functioning as a specimen holder, also as a specimen heating means; a recess 1b, for retaining the specimen on the surface of the filament 1, is provided on a position actually receiving no effect by the thermoelectron from the ion source filament.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a desorption type electron impact ionization mass spectrometer for ionizing a sample in mass spectrometry by using thermal electrons from an ion source filament. In particular, the present invention relates to a direct sample introduction probe for introducing a sample into a mass spectrometer and a filament provided at the tip thereof and functioning as a sample holder.

[0002]

2. Description of the Related Art A mass spectrometer is an analyzer capable of analyzing various substances with high sensitivity (on the order of 10 ^-9 to 10 ^-10 g). A direct sample introduction probe that can be introduced into the ion source is used. Above all, the desorption type electron impact ionization probe is suitable for the analysis of a very small amount of sample because the sample can be directly introduced into the ionization region in the ion source.

[0003] A mass spectrometer equipped with such a desorption type electron impact ionization probe is configured as shown in FIG. That is, the detachable electron impact ionization probe 2 provided with a filament 1 functioning as a sample holder and as a sample heating means at the tip thereof has an internal pressure of a high vacuum (1
0 ^-3 to 10 ^-4 Pa). Here, the filament 1 is usually about 100 μm.
It is composed of a platinum wire having a diameter of m and is inserted into an ionization chamber 4 which is set to a high degree of vacuum (10 ⁻³ to 10 ⁻⁴ Pa) inside the ion source 3. In the ionization chamber 4,
An ion source filament 7 made of a rhenium wire or the like for generating thermoelectrons for ionizing the vaporized sample by electron impact is provided below the tip region 1a of the filament 1. The ionization chamber 4 has a hole 5 for passing the ionized sample in the direction of a detector (not shown).
Is provided above the hole 5, and an electrode group 6 constituting a lens system is provided.

When performing mass spectrometry in such a mass spectrometer, first, the filament 1 holding a sample is used.
The sample is vaporized by resistance heating by applying current to the sample, and the vaporized sample is collided with thermionic electrons emitted from the ion source filament 7 to be ionized. The generated ions pass through the hole 5 and are converged by the electrode group 6 to be detected by a detector (not shown).
And its mass is analyzed.

[0005] When mass spectrometry is performed on a very small amount of a sample using such a probe, it is necessary to sample the sample on a filament provided on the probe. Is collected at the needle point of the manipulator, and the sample collected at the needle point is rubbed against the tip of the filament to perform sampling.

[0006]

However, as shown in FIG. 4, xx in the plan view (FIG. 4A) near the tip region 1a of the filament 1 provided on the probe.
Since the cross section is a very small diameter circle ((b) in the figure), it is difficult to rub the sample on it and to sample it. Even if sampling is successful, the sample is firmly placed on the filament 1. Is not fixed, the sample may be lost before inserting the probe into the ion source of the mass spectrometer.

Further, since the sample is sampled at the tip of the filament 1, the thermoelectrons from the ion source filament 7 directly collide with the sample, and the sample is heated before the filament 1 is heated, that is, before the mass analysis is started. In some cases, the analysis became impossible because all of them were vaporized.

An object of the present invention is to solve the above-mentioned problems of the prior art. A desorption-type electron impact ionization mass spectrometer for ionizing a sample in mass spectrometry by using thermoelectrons from an ion source filament. A sample provided on the tip of a direct sample introduction probe for directly introducing a sample into a sample can be easily sampled and the sampled sample can be stably held, and the sample is vaporized by resistance heating by the filament. In this case, it is an object of the invention not to be affected by the thermoelectrons from the ion source filament.

[0009]

SUMMARY OF THE INVENTION The present inventor has provided a concave portion on the surface of a filament for vaporizing a sample by resistance heating, and the concave portion is not substantially affected by thermoelectrons from an ion source filament. It has been found that the above-mentioned objects can be achieved by providing them at positions, and the present invention has been completed.

[0010] That is, the present invention provides a direct sample introduction probe for directly introducing a sample into a desorption type electron impact ionization mass spectrometer in which ionization of the sample in mass spectrometry is performed by thermal electrons from an ion source filament. And
In the filament functioning as a sample holder and functioning as a sample heating means, a concave portion for holding the sample is provided at a position substantially not affected by the thermoelectrons from the ion source filament. Provide filament.

The present invention also provides a direct sample introduction probe for directly introducing a sample into a desorption type electron impact ionization mass spectrometer in which ionization of the sample in mass spectrometry is performed by thermal electrons from an ion source filament, In a direct sample introduction probe provided with a filament functioning as a sample holder and a sample heating means at its tip, a concave portion for holding the sample on the surface of the filament substantially prevents the influence of thermoelectrons from the ion source filament. The present invention provides a direct sample introduction probe characterized in that it is provided at a position not to receive the sample.

Further, the present invention relates to a desorption type electron impact ionization mass spectrometer for ionizing a sample in mass spectrometry by using thermal electrons from an ion source filament, which functions as a sample holder and as a sample heating means. In a mass spectrometer equipped with a direct sample introduction probe provided with a filament at the tip, a concave portion for holding a sample on the surface of the filament is provided at a position substantially unaffected by thermoelectrons from the ion source filament. And a mass spectrometer characterized in that:

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings.

The filament of the present invention functionally functions as a sample holder for holding a sample, similarly to a conventional filament, and generates heat by conducting electricity, thereby heating and evaporating the sample. Function as For this reason, the filament 1 of the present invention has a structure in which a conductive thin wire is bent as shown in the plan view of FIG. Here, the tip region 1
Since the thermal electrons from the ion source filament collide with a, in the present invention, the concave portion 1b for holding the sample is positioned at a position substantially unaffected by the thermal electrons from the ion source filament, ie, , On the surface of the filament 1 other than the tip region 1a. FIG. 1B shows an example of a cross-sectional view taken along the line xx of the concave portion 1b. By providing the concave portion 1b in this manner, when a very small amount of sample is rubbed with the needle tip of the manipulator, the sample can be easily sampled, and the holding property of the sampled sample is improved. It is possible to prevent the sample from being lost before inserting the probe into the ion source of the mass spectrometer. Further, since the thermoelectrons from the ion source filament do not collide directly, the influence of the thermoelectrons can be eliminated.

As a material of the filament 1, it is preferable to use a platinum wire which does not contaminate the sample and has excellent durability.

Here, the shape of the concave portion 1b is not particularly limited as long as the shape facilitates sampling and holding of the sample. For example, regarding the xx cross-sectional shape in FIG. 1A, the concave portion 1b has a triangular shape in FIG. 1B, but may have a semicircular shape as shown in FIG. It may have a rectangular shape (FIG. 2B). Further, a plurality of recesses 1b may be present (FIG. 2C). Further, the surface of the concave portion 1b may be flattened (FIG. 2D). Also,
In order to facilitate the sampling of the sample, as shown in FIG. 1B and FIGS. 2A to 2D, the tip 1c of the concave portion 1b is preferably formed to have a corner. As shown in FIG. 2E, a smooth curve can be formed.

In the embodiments shown in FIGS. 1 and 2, the concave portion 1b is exemplified by a linear concave portion in a direction perpendicular to the xx direction. A concave portion may be formed, or a line-shaped concave portion (not shown) oblique to the xx direction or the yy direction may be formed. Also, a cross-shaped concave portion or a lattice-shaped concave portion may be formed by combining them (not shown). In addition to the line shape, a concave portion having a curved shape or a circular hole shape may be formed (not shown). Also, the depth and width of the concave portion are not particularly limited, and can be appropriately selected depending on the type of the material of the conductive wire to be used, the amount of the sample to be analyzed, and the like.

The formation of the concave portion in the filament of the present invention is as follows.
It can be done manually with a razor or with a micromachining machine.

The filament of the present invention having the above-mentioned advantages is provided by a direct sample introduction method for directly introducing a sample into a desorption type electron impact ion mass spectrometer in which ionization of the sample in mass spectrometry is performed by thermionic electrons from the ion source filament. Very useful as a probe filament. The structure of the direct sample introduction probe can be the same as that of the conventional direct sample introduction probe except that the filament of the present invention is used.

Further, by using this direct sample introduction probe in a mass spectrometer, it is possible to easily perform a trace analysis. The structure of this mass spectrometer can be the same as that of a conventional mass spectrometer except that a direct sample introduction probe having the filament of the present invention is used.

[0021]

The present invention will be described below in more detail with reference to examples.

Example 1 FIG. 1B shows a direct sample introduction probe having a filament having a shape shown in FIG. 1A made of a platinum wire having a diameter of 100 μm, and the filament being used by a human hand using a razor.
As shown in the figure, a linear concave portion having a depth of 50 μm and a width of 70 μm was formed on the surface of the filament 1 outside the tip region 1a.

The concave portion of the filament 1 has a diameter of 20 to
High-molecular organic compound particles of 30 μm were rubbed with the tip of a manipulator. As a result, the sample could be easily sampled in the concave portion and stably held.

When the direct sample introduction probe holding the sample in this manner was mounted on a desorption type electron impact ionization mass spectrometer as shown in FIG. 3, the ion source filament was heated before the resistance heating filament was heated. A good result of mass spectrometry could be obtained without vaporization by thermal electrons from.

Comparative Example 1 Sampling was attempted in the same manner as in Example 1 except that a filament having no concave portion was used. As a result, the sample could not be sampled well, and the sample that could be sampled slightly was also powdered before being inserted into the ion source of the mass spectrometer.

Comparative Example 2 In the same manner as in Example 1, a concave portion was formed at the tip of the filament of the direct sample introduction probe.

When high-molecular-weight organic compound particles having a diameter of 20 to 30 μm were rubbed into the concave portion with a needle of a manipulator, a sample could be easily sampled into the concave portion and stably held. When the direct sample introduction probe holding the sample was attached to a desorption type electron impact ionization mass spectrometer as shown in FIG. 3, the sample was heated by thermionic electrons from the ion source filament before heating the resistance heating filament. Vaporized, and accurate mass spectrometry could not be performed.

[0028]

According to the present invention, a direct sample introduction probe for directly introducing a sample in a desorption type electron impact ionization mass spectrometer in which ionization of a sample in mass spectrometry is performed by thermal electrons from an ion source filament. The sample can be easily sampled on the filament provided at the tip, and the sampled sample can be stably held. Moreover, when the sample is vaporized by resistance heating with a filament,
The effect of thermionic electrons from the ion source filament can be eliminated.

[Brief description of the drawings]

FIG. 1 is a plan view of the filament of the present invention in which a concave portion is formed (FIG. 1A) and a cross-sectional view of the concave portion (FIG. 1B).

FIG. 2 is a cross-sectional view (FIGS. (A) to (e)) of a concave portion of the filament of the present invention.

FIG. 3 is a schematic explanatory view in the case where a sample is ionized using a desorption type electron impact ionization probe and mass analysis is performed.

FIG. 4 is a plan view (FIG. 4A) of a tip region of a filament provided in a conventional direct sample introduction probe and the vicinity thereof (FIG. 4A), and a cross-sectional view thereof (FIG. 4B).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Filament, 2 ... Desorption type electron impact ionization probe, 3 ... Ion source 4 ... Ionization chamber, 5 ... Hole, 6 ... Electrode group, 7 ... Ion source filament

Claims (6)

[Claims] 1. A sample holder provided at a tip of a direct sample introduction probe for directly introducing a sample into a desorption type electron impact ionization mass spectrometer for ionizing the sample in the mass spectrometry by thermionic electrons from an ion source filament. A filament which functions as a sample heating means and has a concave portion for holding a sample provided at a position substantially not affected by thermal electrons from an ion source filament. 2. The filament according to claim 1, wherein the filament is a platinum wire. 3. A direct sample introduction probe for directly introducing a sample into a desorption type electron impact ionization mass spectrometer for ionizing the sample in mass spectrometry by using thermal electrons from an ion source filament, the sample being provided at the tip thereof. In a direct sample introduction probe provided with a filament functioning as a holder and functioning as a sample heating means, a concave portion for holding a sample on the surface of the filament is substantially not affected by thermoelectrons from the ion source filament. A direct sample introduction probe, which is provided at a position. 4. The direct sample introduction probe according to claim 3, wherein the filament is a platinum wire. 5. A desorption-type electron impact ionization mass spectrometer for ionizing a sample in a mass spectrometer using thermoelectrons from an ion source filament, wherein a filament functioning as a sample holder and functioning as a sample heating means is provided at the tip. In the mass spectrometer provided with the provided direct sample introduction probe, the concave portion for holding the sample on the surface of the filament is provided at a position substantially not affected by the thermoelectrons from the ion source filament. A desorption type electron impact ionization mass spectrometer characterized by the following. 6. The desorption electron impact ionization mass spectrometer according to claim 5, wherein the filament is a platinum wire.