JPH0317093B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mass spectrometer, and particularly to a so-called mass spectrometer in which a second electric field is added to the rear stage of a double-focus mass spectrometer system.
Regarding MS/MS equipment.

Recently, so-called mass spectrometry systems have been developed in which a mass spectrometry system is placed after a double convergence mass spectrometry system that combines an electric field and a magnetic field.
MS/MS instruments have been proposed. This MS/MS
In the device, specific precursor ions selected with high accuracy by the first mass spectrometry system are introduced into a collision chamber placed between the two analysis systems, where they are split and dissociated, and the generated daughter ions are sent to the second analysis system. The daughter ions are introduced into the system and swept by the analysis system to obtain the mass spectrum of the daughter ions.Since the first analysis system can select the precursor ions with high precision, the obtained spectrum has a high resolution with respect to the precursor ions. It has the characteristic of being extremely high. In particular, using an electric field as the second analysis system does not require a very complicated configuration and is advantageous in terms of cost.
MS devices are attracting attention.

However, this type of MS/MS apparatus has the drawback that although the spectrum obtained as described above has high resolution for precursor ions, it does not have high resolution for daughter ions, and a sharp spectrum cannot be obtained.

On the other hand, it has also been conventionally possible to obtain daughter ion spectra using a single double-focusing mass spectrometer without adding a second electric field or the like. This method is called the linked scan method, and by keeping the ratio of the strengths of the electric and magnetic fields that make up the double convergence mass spectrometry system constant and sweeping the two fields in conjunction,
The spectrum of daughter ions dissociated from a specific precursor ion is obtained between an ion source and an electric field.

Using this linked scan method, it is possible to obtain daughter ion spectra with extremely high resolution, but the resolution for precursor ions is low. The disadvantage was that the peaks of the daughter ions that were generated were mixed in.

The present invention has been made in view of the above-mentioned points, and is an MS/MS equipped with an electric field as a second analysis field.
Applying the linked scan method to the MS device, the electric and magnetic fields of the first mass spectrometry system and the second electric field are
By sweeping while keeping the ratio of the respective intensities constant, it is possible to obtain sharp daughter ion spectra with high resolution even with an MS/MS instrument. The object of the present invention is to provide a new mass spectrometer that can be improved over the linked scan method in a double convergence mass spectrometer.

Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 shows the configuration of an embodiment of the present invention, in which 1 indicates an ion source consisting of an ionization box, a slit, etc.;
2 is the main slit, 3 is the ion source 1 and main slit 2
and a first collision chamber disposed between the first and second collision chambers. The ions taken out from the main slit 2 are transferred to the concentric cylindrical electrode 4,
After entering the double convergence mass spectrometry system 6, which consists of an electric field _E1 formed between 4' and a magnetic field B formed between magnetic poles 5 and 5' (magnetic pole 5' is not shown), the It is converged to the position. A second collision chamber 8 is arranged near the intermediate slit 7, and the ions that have passed through the collision chamber 8 are affected by an electric field E2 formed between concentric cylindrical electrodes 9 and 9' arranged behind the second collision chamber 8. The ion beam passes through the ion detector 10 and is detected by the ion detector 10. The detection signal obtained from the detector 10 is supplied to a recorder 12 via an amplifier 11 and recorded. The recorder 12 is supplied with a sweep signal from a sweep signal generator 13, and the sweep signal is supplied to the electric field power sources 14, 15 for applying voltage between the cylindrical electrodes 4, 4' and 9, 9'. , and a magnetic field power source 1 that supplies current to the coil for exciting the magnetic poles 5 and 5'.
It will also be sent to 6. 17 is a potentiometer for dividing the voltage of the sweep signal and sending it to the magnetic field power supply 16.

In such a configuration, the second collision chamber 8 is not directly necessary for the present invention, so it may be removed from the ion path or
Alternatively, it is not filled with collision gas and is allowed to pass through ions as is. Here, ion source 1
If the ion generated in is m ₀ ⁺ , the ion collides with molecules of a collision gas such as argon existing at an appropriate pressure in the collision chamber 3, and dissociates according to the following formula to form daughter ions m ₁ ⁺ is generated.

m ₀ ⁺ →m ₁ ⁺ +(m ₀ −m ₁ ) …(1) If the precursor ion m ₀ ⁺ has an energy of Va, this daughter ion m ₁ ⁺ has the energy Va×(m ₁ /m ₀ )
It has the energy of In this way, the intensity E ₁ d of E ₁ that allows a daughter ion having a mass of m ₁ and an energy of Va×(m ₁ /m ₀ ) to pass through the electric field E ₁ is expressed by the following equation.

E ₁ d=E ₁₀ ×(m ₁ /m ₀ ) (2) Here, E ₁₀ is the intensity at which the precursor ion m ₀ ⁺ can pass through the electric field E ₁ .

Next, the strength Bd of the magnetic field B that allows the daughter ions to pass through the magnetic field B is expressed by the following equation.

Bd ² =B ₀ ² ×(m ₁ /m ₀ ) ² (3) where B ₀ is the strength at which the precursor ion m ₀ ⁺ can pass through the magnetic field B.

Furthermore, the intensity E ₂ d of E ₂ with which the daughter ion can pass through the electric field E ₂ is expressed by the following equation similarly to E ₁ .

E ₂ d=E ₂₀ ×(m ₁ /m ₀ ) (4) Here, E ₂₀ is the intensity at which the precursor ion m ₀ ⁺ can pass through the electric field E ₂ .

In order for the daughter ions to pass through all of the electric field E ₁ , magnetic field B, and electric field E ₂ and reach the ion detector 10, the above equations (2), (3), and (4) must hold simultaneously. It is. Therefore, by rearranging equations (2), (3), and (4), the following equation is obtained.

E ₁₀ ² /B ₀ ² =E _1d ² /B _d ² …(5) E ₂₀ ² /B ₀ ² =E _2d ² /B _d ² …(6) Furthermore, rearrange equations (5) and (6) Then, the following equation is obtained.

E _1d /E ₁₀ =B _d /B ₀ =E _2d /E ₂₀ ...(7) From this equation (7), the electric field E ₁ , magnetic field B, and electric field when the precursor ion m ₀ ⁺ reaches the ion detector are With the intensities E ₁₀ , B ₀ , and E ₂₀ of E ₂ as initial values, the intensities of the electric field E ₁ , magnetic field B, and electric field E ₂ are respectively changed to E _1d , B _d , and E _2d toward zero intensity, Always E _1d :
_E 1d so that B _d : E _2d = E ₁₀ : B ₀ : E ₂₀ is satisfied,
If the ratio of B _d and E _2d is maintained, only the daughter ions derived from the precursor ion m ₀ ⁺ will reach the ion detector. The spectrum of the daughter ion derived from the precursor ion m ₀ ⁺ will be obtained.

Note that this daughter ion spectrum is determined by the second electric field.
The effect of _E2 allows the energy of the daughter ion to be identified and passed, so that a specific precursor ion
The probability that a daughter ion derived from a precursor ion other than m ₀ ⁺ passes through the electric field E ₂ and reaches the ion detector is:
This is much smaller than when a linked scan is performed using a single double-focusing mass spectrometer. Therefore,
Resolution for precursor ions is improved over linked scan with a single dual focus mass spectrometer.

The measurement procedure is to first introduce precursor ions m ₀ ⁺ into the analysis system without introducing collision gas into the collision chamber 3, and allow the ions m ₀ ⁺ to pass through the analysis system and enter the detector 10. For example, manually adjust _{the intensities E 10 ,} B ₀ , E ₂₀ of E 1 , B, E ₂ such that
16, 15 and potentiometer 17, and the initial values of E ₁ , B, and E ₂ are respectively
Each power supply 14 is set to E ₁₀ , B ₀ , E ₂₀ ,
16, 15 and potentiometer 17.

When the sweep circuit 13 is then activated, it generates a sweep signal as shown in FIG. 2a.
Each power supply 14, 16, 15 is based on the sweep signal.
As shown in Figure ₂ b, c, and d, E 1 , B , and E ₂ are moved all at once toward zero from the initial values E ₁₀ , B ₀ , and E ₂₀ while keeping the ratio of E ₁ :B:E ₂ constant. Sweep. Therefore, at the start of the sweep, precursor ions that were not dissociated in the collision chamber 3 are passed through the analysis system and detected, and thereafter daughter ions derived by dissociation are sequentially passed through the analysis system and detected in descending order of mass number. Therefore, by introducing the detection signal into the recorder 12 that is swept by the sweep signal and recording it, a mass spectrum in which peaks of daughter ions are sequentially depicted starting from the precursor ion can be obtained. This mass spectrum is analyzed because the daughter ion is analyzed by the electric field E ₁ and magnetic field B, which satisfy the double convergence condition.
The resolution for the mass of the daughter ion is high, resulting in a sharp spectrum.

In the above example, the precursor ions collided with gas molecules in the collision chamber 3 and were dissociated. Some dissociate spontaneously. In that case, the collision chamber 3 is not necessary, and the collision chamber 3 may be removed from the ion passageway or the ions may be allowed to pass through without being filled with gas.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an embodiment of the present invention, and FIG. 2 is a diagram for explaining its operation. 1: Ion source, 3: Collision chamber, 4, 4', 9,
9': Concentric cylindrical electrode, 5, 5': Magnetic pole, 10: Ion detector, 12: Recorder, 13: Sweep circuit, 1
4, 15: Electric field power supply, 16: Magnetic field power supply.

Claims (1)

[Claims] 1. an ion source, a double focus mass spectrometry system having an electric field _E1 and a magnetic field B into which precursor ions generated by the ion source and daughter ions dissociated from the precursor ions are introduced, and the double focus mass spectrometry system an ion detector for detecting ions that have passed through the ion detector; a recording means for recording a detection signal from the ion detector; a second electric field _E2 , an electric field _E1 and a magnetic field B constituting the double focusing mass spectrometry system, and a power supply means for generating the second electric field _E2 , and a sweep signal generator for generating a sweep signal. and the power supply means includes an electric field _E1 and a magnetic field B constituting the double focus mass spectrometry system and the second electric field.
The intensity of each field E ₂ when the target specific precursor ion reaches the ion detector is E ₁₀ ,
With B ₀ and E ₂₀ as initial values, the intensity ratio of the three is always
A mass spectrometer characterized in that the intensity is swept toward zero based on the sweep signal while E ₁₀ :B ₀ :E ₂₀ is kept constant.