Mass spectrometer

Abstract

In a mass spectrometer in which a high ion dissociation efficiency is possible, inserted electrodes are arranged with a form divided into two or more in the axial direction of the ion trap, an electric static harmonic potential is formed from a DC voltage applied to the inserted electrodes, and with an Supplemental AC voltage applied, ions in the ion trap are oscillated between the divided inserted electrodes in the axial direction of the ion trap by resonance excitation, and the ion with a mass/charge ratio within a specific range is mass-selectively dissociated. Thus, a high ion dissociation efficiency is realized by the use of ion trap of the present invention.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graphical representation of an example to show a problem with a prior art;

FIG. 2 is a schematic sectional view of the spectrometer used in the first embodiment of the present invention;

FIG. 3A is a block diagram of the power supply connected to the inserted electrodes in longitudinal section of the spectrometer used in FIG. 2;

FIG. 3B is a block diagram of the power supply connected to the rod electrodes in transverse section at B-B of the spectrometer used in FIG. 2;

FIG. 3C is a block diagram of the power supply connected to the rod electrodes in transverse section at C-C of the spectrometer used in FIG. 2;

FIG. 4 is the operating sequence of the voltages applied to the electrodes shown in FIGS. 3A-3C for ion dissociation;

FIG. 5 is an example of mass spectrum obtained with a system and procedure of FIGS. 2-4 for the same ions in FIG. 1;

FIG. 6 shows the variation of dissociation efficiency for a TBA (m/z 242) as a function of static harmonic potential depth D;

FIG. 7A is a block diagram of the power supply connected to the inserted electrodes in longitudinal section of the spectrometer used in FIG. 2;

FIG. 7B is a block diagram of the power supply connected to the rod electrodes in transverse section at B-B of the spectrometer used in FIG. 2;

FIG. 7C is a block diagram of the power supply connected to the rod electrodes in transverse section at C-C of the spectrometer used in FIG. 2. The above system is used in the second embodiment and similar to that shown in FIGS. 3A-3C except that the sample ion can be isolated in the quadrupole linear ion trap 13 (not shown);

FIG. 8 is the operating sequence of the voltages applied to the electrodes shown in FIGS. 7A-7C for ion dissociation in the second embodiment;

FIG. 9 is the operating sequence of the voltages applied to the electrodes shown in FIGS. 7A-7C for ion dissociation in the third embodiment;

FIG. 10 is a schematic sectional view of the spectrometer used in the fourth embodiment of the present invention.

FIG. 11 is the operating sequence of the voltages applied to the electrodes shown in FIG. 10 for ion dissociation in the fourth embodiment of the invention;

FIG. 12 is the operating sequence of the voltages applied to the electrodes similar to those shown in FIG. 10 for ion dissociation in the fifth embodiment of the invention;

FIG. 13 is the operating sequence of the voltages applied to the electrodes similar to those shown in FIG. 10 for ion dissociation in the sixth embodiment of the invention;

FIG. 14A shows a mass spectrum of all ions generated in the ion generation unit for reserpine;

FIG. 14B shows a mass spectrum of the isolated sample ion (m/z 609.3); and

FIG. 14C shows a mass spectrum of the dissociated fragment ions obtained from the sample ion.

Claims

1. A mass spectrometer comprising: an ion source for generating ions;an ion trap for at least two of storing, isolating, dissociating, and removing ions;electric-field forming electrodes for forming an electric field along the axial direction of the ion trap, wherein the electric field is formed from an electrostatic potential;a power supply unit for controlling operation of the ion trap; anda detector for detecting ions ejected from the ion trap;wherein the power supply includes an Supplemental AC power supply applying a Supplemental AC voltage to the electric field forming electrodes, and with the Supplemental AC voltage applied to the electric field forming electrodes, the ions in the ion trap are oscillated in the axial direction of the ion trap by resonance excitation, and thereby the ions within a predetermined mass/charge ratio range are mass-selectively dissociated.

2. The mass spectrometer according to claim 1, wherein the electric field forming electrodes are inserted electrodes being divided into two or more in the axial direction of the ion trap.

3. The mass spectrometer according to claim 1, wherein the electro static potential has a depth of higher than or equal to 5 V.

4. The mass spectrometer according to claim 1, further comprising an ion isolation unit for isolating ions generated from the ion source arranged between the ion generating unit and the ion trap.

5. The mass spectrometer according to claim 1, wherein by the application of the Supplemental AC voltage from the Supplemental AC power supply, the ions in the ion trap are oscillated in the axial direction of the ion trap via resonant excitation, and thereby an ion with a specific mass/charge ratio is isolated mass-selectively.

6. The mass spectrometer according to claim 1, wherein the ion trap further comprises a plurality of rod electrodes, and the power supply has a secondary Supplemental AC power supply, and wherein, by application of the secondary Supplemental AC voltage to the rod electrodes, the ions in the ion trap are oscillated in the radial direction of the ion trap via resonant excitation, and thereby the ion with a mass/charge ratio within the predetermined range is isolated mass-selectively.

7. The mass spectrometer according to claim 1, wherein the ion in the ion trap is ejected by scanning a frequency of the Supplemental AC voltage applied by the Supplemental AC power supply.