JP3282165B2 - Cleavage ion mass spectrometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleavage ion mass spectrometer of the type which obtains analysis information by mass analysis of daughter ions generated by a cleavage reaction of ions (parent ions) selected in a pre-stage mass spectrometer.

[0002]

2. Description of the Related Art FIG. 4 shows a conventional device (US Pat. No. 4,423,479).
1) is shown. In this figure, reference numeral 1 denotes a pre-stage mass spectrometer in which a quadrupole mass spectrometer is used. Reference numeral 2 denotes a subsequent mass spectrometer, which is also a quadrupole mass spectrometer. A cleavage chamber 3 is provided between the first and second mass spectrometers 1 and 2, and a quadrupole ion lens 4 is disposed in the same. A collision gas is introduced into the cleavage chamber 3. The ions (parent ions) having a specific mass selected by the former-stage mass analyzer 1 enter the latter-stage mass analyzer 2 via the cleavage chamber 3. The sample component molecules ionized by various methods are metastable ions, and mass spectrometry is performed in normal mass spectrometry, but this ion is further gradually cleaved to generate multiple types of daughter ions. . The mass spectrometry of the daughter ion is performed here. The daughter ion cleaved while passing through the cleavage chamber 3 is subjected to mass spectrometry in the mass spectrometry unit at the subsequent stage, and the parent ion is cleaved. The mass spectrum of the generated daughter ion is measured. Although the cleavage of the parent ion occurs spontaneously, a collision gas is introduced into the cleavage chamber 3 since the cleavage reaction can be promoted by colliding with a suitable gas molecule. Since the daughter ions that have been cleaved in the cleaving chamber have a tendency to diverge before that, the incidence efficiency to the subsequent mass spectrometer is low. A quadrupole ion lens 4 is used to suppress and converge the divergence of the daughter ions and to efficiently introduce the daughter ions to the mass analyzer 2 at the subsequent stage.

The quadrupole ion lens 4 is applied with only an appropriate high-frequency voltage and has no mass selection function, and is provided only for ion focusing. However, in practice, the electric field near both ends of the quadrupole ion lens 4 is disturbed by the action of the electric field leaking out from the ion exit end of the former stage mass analyzer 1 and the ion entrance end of the latter stage mass analyzer 2. Therefore, the ion trajectory was disturbed, and the ion transmittance of the lens was reduced. Moreover, this decrease is not uniform with respect to the mass, and the decrease is large on the high mass side, and furthermore, it fluctuates up and down depending on the mass as shown in FIG. For this reason, the quantitative accuracy of the mass spectrum is reduced. However, conventionally, as a countermeasure against this, the ions are accelerated between the front and rear mass spectrometers and the ion lens 4 to reduce the ion transit time of the portion where the electric field is disturbed. Although measures were taken to reduce the effects of turbulence by shortening, sufficient effects were not obtained.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to prevent the ion transmittance of a quadrupole ion lens 4 from being changed by mass and to improve the quantitative and qualitative accuracy of mass spectrometry.

[0005]

A quadrupole ion lens 4 is provided.
An AC voltage was superimposed on the applied voltage or the acceleration voltage between the quadrupole ion lens 4 with the mass spectrometers 1 and 2.

[0006]

The mass dependence of the ion transmittance of the quadrupole ion lens 4 shown in FIG. 2 is the same under the same conditions with the same apparatus, that is, the selected mass of the preceding ion, the acceleration voltage between the preceding and succeeding mass analyzer and the ion lens 4, If the applied voltage and the like of the heavy ion lens 4 are kept constant, reproducibility can be obtained. However, if these conditions are changed, the shape of the characteristics changes. For this reason, if the above-mentioned acceleration voltage or the voltage applied to the ion lens is changed at an appropriate cycle, FIG.
The shape of the characteristic graph, especially the shape of the portion that fluctuates depending on the mass on the high mass side, changes, and these different characteristics are superimposed and averaged, resulting in the transmission characteristics as shown in FIG. Here, the period of the periodic change of the voltage or the like applied to the ion lens includes several periods within the period in which one spectral peak is detected in mass scanning, and one smooth signal is generated by the averaging operation. It is sufficient that the frequency is at least as high as possible and lower than the high frequency applied to the quadrupole ion lens.

[0007]

FIG. 1 shows an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a pre-stage mass spectrometer which uses a quadrupole mass spectrometer, but it may be a magnetic field type. Reference numeral 2 denotes a subsequent mass spectrometer, which also uses a quadrupole mass spectrometer. Reference numeral 3 denotes a cleavage chamber, which is formed in a vacuum vessel V so that collision gas can be introduced. Reference numeral 4 denotes a quadrupole ion lens installed in the cleavage chamber. 5 is an ion source,
Reference numeral 6 denotes an ion lens which converges ions emitted from the ion source and causes the ions to enter the mass spectrometer 1. Reference numeral 7 denotes an ion detector.

Reference numeral 10 denotes a DC and high-frequency variable voltage source applied to the quadrupole of the front-stage mass analyzer 1, and 11 denotes a DC and high-frequency variable voltage source also applied to the rear-stage mass analyzer 2. Reference numeral 12 denotes a high-frequency voltage source applied to the quadrupole ion lens 4. A DC power supply 13 is connected to the cleavage chamber 3 so that ions emitted from the mass spectrometric unit 1 are accelerated to enter the cleavage chamber 3. The purpose of this acceleration is to provide collision energy for promoting cleavage when ions collide with collision gas molecules in the collision chamber. With this device, appropriate DC and high-frequency voltages are applied to the quadrupole of the pre-stage mass analyzer 1 so that parent ions of a specific mass enter the cleavage chamber 3. The parent ion is cleaved in the cleavage chamber, and ions of lower mass (daughter ions) generated by the cleavage are incident on the subsequent mass spectrometer 2 with the parent ion not cleaved as the maximum mass ion. When mass scanning is performed by changing the voltage while appropriately maintaining the applied DC and high frequency voltage ratios in the subsequent mass spectrometer 2, the mass of daughter ions generated by the cleavage reaction from the ions selected by the premass spectrometer 1 is obtained. A spectrum is obtained.

Reference numeral 14 denotes an AC power supply for generating an AC voltage to be added to the high-frequency power supply 12, and the output voltages of the two power supplies are added to be applied to the quadrupole of the ion lens 4. Due to this AC voltage, the form of the vertical fluctuation on the high mass side of the transmittance characteristic shown in FIG. 2 changes, and the transmittance characteristic is averaged to have no irregularities. Assuming now that the mass of the parent ion is 1000, the mass of the daughter ion is 1000 or less, and the mass scanning range of the subsequent mass spectrometer 2 is 0 to 1000, but in practice, it may be, for example, about 100 to 1000. If a mass scan is performed in one second, a mass of 100 to 1000 can be up to 90.
Zero spectral peaks appear (because a mass spectrum appears one mass jump for one proton), and the frequency of appearance of the spectral peaks is 900 Hz. Assuming that the peak width of the mass spectrum is １ ／ of this one cycle, the time width of the peak of the mass spectrum is 1/900 × 5 = 1/4500 seconds. If the period of the AC power supply 14 is set to 10 during this time, the output frequency of the AC power supply 14 becomes 45000 Hz.
= 45 KHz.

In the above embodiment, the low frequency voltage is superimposed on the high frequency applied to the quadrupole lens 4, but the low frequency voltage may be superimposed on the DC voltage applied to the collision chamber 3. Further, in the above-described embodiment, the quadrupole lens 4 is installed in the ion cleaving chamber 3, but the same effect can be obtained with other multipole electrodes such as a large pole type and an octupole type. Further, in the above-described embodiment, it is also possible to superimpose a slightly shifted high frequency on the high frequency applied to the quadrupole lens 4 and generate a low frequency as the difference.

[0011]

According to the present invention, the change in the ion transmittance of the ion lens 4 due to the mass is averaged and flattened, and the sensitivity difference due to the ion mass is eliminated, thereby improving the quantitative and qualitative accuracy of the analysis.

[Brief description of the drawings]

FIG. 1 is a side view of one embodiment of the present invention.

FIG. 2 is a graph showing transmittance characteristics of a conventional quadrupole ion lens unit.

FIG. 3 is a graph of transmittance characteristics improved by the present invention.

FIG. 4 is a side view of a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 front stage mass analysis unit 2 rear stage mass analysis unit 3 collision chamber 4 quadrupole ion lens 5 ion source 7 ion detector 10 voltage source of front stage mass analysis unit 11 voltage source of rear stage mass analysis unit 12 quadrupole ion lens Voltage source 13 Ion acceleration voltage source 14 AC power supply

Claims (2)

(57) [Claims] 1. A cleavage ion mass spectrometer of a type in which a multipole ion lens for ion convergence is arranged in an ion cleavage chamber between a mass analysis unit at a front stage and a mass analysis unit at a rear stage,
For the superimposed voltage of a high frequency voltage or high-frequency and DC applied to the multipole ion lens, modulating the added or heavy
Cleavage ion mass spectrometer which is characterized by providing an AC power source for applying an AC voltage to tatami. 2. A cleavage ion mass spectrometer of a type in which a multipole ion lens for ion focusing is disposed in an ion cleavage chamber between a mass analysis unit at a front stage and a mass analysis unit at a rear stage.
In order to accelerate ions between the pre-stage mass spectrometry section and the ion cleavage chamber, an AC power supply for superimposing and applying an AC voltage to a DC voltage applied to the ion cleavage chamber is provided. Ion mass spectrometer.