JPS58197646A - Method of ionization - Google Patents

Abstract

PURPOSE:To provide a method of ionization that can obtain the mass spectra of a sample which is difficult to dissolve in glycerin by ionization. CONSTITUTION:After a target 5 whose solidified sample surface is coated with glycerin is set, the inner part of an ionized chamber 13 is exhausted to get a vacuum and an argon ion is generated from an ion gun 1. The argon ion is deflected by an electrostatic deflection plate 4 and as a result, only the neutral argon atomic beam is incident on the target 5. Besides, the target 5 is electrified and heated by a power supply 12 and as a result, the glycerin on the surface is evaporated by the heating and the impact caused by the neutral argon atomic beam. The evaporated glycerin is further ionized by the energy of the neutral beam and is guided to a mass spectrometer section through the slit 9 of an electrode 10. As a result, the mass spectra obtained in the initial state are based on only glycerin, but the mass spectra of a sample can be obtained since the ion of glycerin is reduced with a lapse of time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ionization method suitable for use in a mass spectrometer, and particularly to an ionization method in which a sample is bombarded with high-speed neutral particles to ionize the sample.

In recent years, a method has been developed in which a mixed sample of, for example, glycerin and a substance to be ionized is coated on a conductive substrate, the sample is bombarded with high-speed neutral particles, and the substance to be ionized is knocked out by the energy of the neutral particles and further ionized. ion sources are attracting attention. When used as an ion source for a mass spectrometer, this ion source has low ionization energy and soft ionization, a high generation rate of not only positive ions but also negative ions, and additionally, it bombards the sample with neutral particles. Because of this, it has many excellent features such as no charge-up and the ability to easily ionize even insulating samples.

By the way, when using this ion source to ionize a sample that is difficult to dissolve in glycerin, the sample is first dissolved in a solvent in which the sample is easily soluble, and the mixed substance of the solvent and sample is stirred with glycerin to form a colloidal sample. This colloidal sample is then applied onto the target. However, when such a sample is ionized to obtain a mass spectrum, the spectrum of glycerin appears extremely strong, and the spectrum of the sample tends to be relatively weak, and in severe cases, no spectrum of the sample can be obtained at all. It has become clear that there are cases.

The purpose of the present invention is to provide an ionization method that makes it possible to ionize a sample that is difficult to dissolve in glycerin and obtain a mass spectrum of the sample.
After applying a sample to the target and further applying glycerin to the surface of the sample, the target is heated and neutral particles are irradiated toward the target to which the sample is applied.

An embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows an example of an ion source for carrying out the present invention. In the figure, 1 is an argon ion gun, and argon ions generated in the ion gun are accelerated by an accelerating electrode 2. As shown in FIG. This accelerated high-velocity argon ion beam enters the collision chamber 3 filled with argon gas, and a portion of it collides with the argon gas and is stripped of charge, becoming high-speed neutral particles. An electrostatic deflection plate 4 is disposed at the bottom of the collision chamber 4, and the collision chamber 3. The argon ions that have passed are deflected and removed, and only neutral argon particles that have been deprived of charge are incident on a plate-shaped target 5 disposed below the deflection plate 4. The target 5 is a base 6. It is attached to the pillars 7 and 8 of the top by spot welding, and is provided with a large number of needle-like members of fine diameter. Close to the target 5 and open the slit 9
An electrode 10 having a target 5 is arranged.
A voltage of about 10 V, for example, is applied from the voltage source 11 between the electrode 10 and the electrode 10 . Further, the pillars 7 and 8 are connected to a heating power source 12 for electrically heating the target 5. Here, the target 5 having the large number of needle-like materials is manufactured, for example, by the following method. First, gold is deposited on the surface of a plate-shaped base material made of tungsten, and then the base material is placed in a silane gas (SiH 45% to 18% to 95%) atmosphere. Furthermore, by applying electricity to the tungsten base material and heating it, a large number of silicon needles with a diameter of about 0.2)1 m and a length of about 20 mm grow on the gold-deposited surface after about 1 to 10 minutes. Then, the target 5 is manufactured.

Note that the shape of the target 5 may not be a plate shape, but may be a wire shape.

During ionization using the above-described configuration, the target portion is first taken out of the ion chemistry 13, and a sample dissolved in a volatile solvent such as acetone or alcohol is applied thereto. Thereafter, only the solvent on the target is evaporated, only the sample is solidified on the target, and furthermore, glycerin is applied to the solidified surface. After applying this glycerin, the target 5 is set at a predetermined position in the ionization chamber 13. After the target 5 is set, the ionization chamber is evacuated and argon ions are generated from the ion gun 1.

A considerable portion of the argon ions generated and accelerated from the ion gun 1 mainly collide with argon atoms in the collision chamber 3 and lose their charge. A mixed beam of neutral high-speed argon atoms and argon ions that have not lost their charge in the collision chamber is obtained from the collision chamber 3, but the argon ions are deflected by the electrostatic deflection plate 4, resulting in neutral Only the argon atomic beam enters the target 5. Furthermore,
The target 5 is electrically heated by a power source 12,
As a result, the surface glycerin is evaporated by heating and bombardment with a beam of neutral argon atoms. The evaporated glycerin is further ionized by the energy of the neutral beam and guided through the slit 9 of the electrode 10 to the mass spectrometer. Therefore, in the initial state, it is analyzed by the mass spectrometer and the obtained mass spectrum is based only on glycerin, but as time passes, the amount of glycerin ions generated from the target decreases, and after a certain amount of time has passed. The sample that was later covered by glycerin also begins to be ionized.

Figure 2 shows the amount of ions in glycerin and the sample that are ionized and introduced into the mass spectrometer, and the horizontal axis in the figure is time;
The vertical axis is the ion amount, Io is glycerin, and ls is the sample. From this figure, it is clear that the number of glycerin ion ports decreases rapidly, and that the sample is actively ionized with a small amount of glycerin remaining on the sample surface, and this state continues for a considerable time. Therefore, if mass spectrometry is performed in a state where glycerin ions are reduced, a mass spectrum of the sample can be obtained in a state where the influence of glycerin can be ignored.

In Figure 3(a), adenosine, which is difficult to dissolve in glycerin, is used as a sample, and the adenosine and glycerin are mixed.
This is a mass spectrum obtained by a conventional method in which adenosine was applied to the target with stirring and ionized by the ion source shown in Figure 1. Figure 3(b) shows a mass spectrum obtained by first applying adenosine to the target. This is a mass spectrum obtained by applying glycerin to cover the surface of the target after drying and ionizing the target according to the present invention in which neutral particles are bombarded while heating the target. By using the present invention, the peak pa of adenosine can be clearly detected, as is clear from the spectrum shown in FIG. 3(b). On the other hand, in FIG. 3(a) obtained by the conventional method, only the glycerin peak PO is detected as large, and the adenosine peak is extremely small, making it difficult to distinguish it from the noise peak. This Figure 3 shows the case where adenosine was used as the sample, but we also conducted experiments with cholesterol, etc., which are difficult to dissolve in glycerin and have difficulty obtaining mass spectra using conventional methods. The results were obtained.

As detailed above, the present invention is particularly effective when used to ionize samples that are difficult to dissolve in glycerin. Note that the present invention is not limited to the embodiments described above, and can be modified in many ways. For example, the target to which the sample is applied may be a plate or wire without a large number of fine needle-like members, but in this case, the sample is held less, which is disadvantageous.

[Brief explanation of the drawing]

Figure 1 is a diagram showing an example of an ion source used to carry out the method based on the present invention, Figure 2 is a diagram showing the ion amounts of glycerin and sample, and Figure 3 is a diagram showing an example of the ion source used to carry out the method based on the present invention. FIG. 2 is a diagram showing a mass spectrum obtained by the method based on FIG. 1: Ion gun 3: Collision chamber 5: Target 6: Base 7.8 = Support 9 Nislit 10: Electrode 11: Power source 12: Heating power source 13: Ionization chamber Patent applicant JEOL Ltd. Representative Tadao Kase

Claims (1)

[Claims] An ionization method in which a sample is coated on a target, glycerin is further coated on the surface of the sample, the target is heated, and neutral particles are irradiated toward the target on which the sample is coated.