JPH0375979B2 - - Google Patents

Description

[Detailed Description of the Invention] A. Field of Industrial Application When sample molecules are ionized in a mass spectrometer, various types of fragment ions are generated, but some of these ions themselves can be dissociated into smaller ions and neutral molecules. There are ions in a metastable state. In this case, what kind of ion (daughter ion) is produced when a metastable ion of a certain mass is dissociated, and the mass spectrum of the daughter ion is determined by This provides useful information in determining whether the sample was a substance and, ultimately, what the molecular structure of the original sample was. The present invention relates to an apparatus for obtaining a mass spectrum of daughter ions generated from a parent ion of a specified mass.

B. Prior art The apparatus for obtaining the mass spectrum of daughter ions generated from one kind of parent ion is a magnetic field-preceding double focusing mass spectrometer that combines a magnetic field and an electric field. The device is designed to sweep the electric field and analyze the energy of ions that have passed through the magnetic field.

In the fission reaction of metastable ions, the velocities of the parent ion and daughter ion can be considered to be the same, so if the mass of the parent ion is Mo, the kinetic energy is Eo, the mass of the daughter ion is M, and the energy is E, then M=E. /EoMo relationship is established. In the above equation, Eo is determined by the ion acceleration voltage, and a certain value for Mo is selected by the magnetic field settings, so the mass spectrum of the daughter ion can be obtained by changing the electric field voltage and performing energy scanning. .

The method described above is based on MIKES (Mass−analysed Ion
Although conventional MIKES can only obtain the mass spectrum of daughter ions generated from one type of parent ion, it is possible to simultaneously measure the mass spectra of each daughter ion of multiple parent ions. There are times when you want to do it. For example, if one of multiple types of parent ions is used as an internal standard,
Quantitative comparisons between the spectra of its daughter ions and the daughter spectra of other parent ions provide analytically important information, but when such measurements are made on the effluent sample from a chromatograph, multiple parent ions are present. For practical purposes, it is necessary to be able to measure ions simultaneously, but conventional methods have not been able to perform such measurements.

C. Problems to be Solved by the Invention The present invention provides a method that can practically simultaneously measure mass spectra of parent ions generated from multiple types of parent ions.

D. Means for solving the problem Energy scanning was performed by keeping the magnetic field constant and periodically sweeping the electric field voltage, and switching the ion accelerating voltage every cycle of the energy scanning.

E. Effect It is possible to sweep the voltage of an electric field for energy analysis at high speed, but it is difficult to sweep a magnetic field for mass spectrometry at high speed. On the other hand, in order to obtain spectra of daughter ions from multiple types of parent ions, it is necessary to switch the ions selected by the mass spectrometer to multiple types, and this must be done at high speed. Since switching the accelerating voltage is used, switching of parent ions is performed at high speed, making it possible to practically simultaneously measure the mass spectra of daughter ions from multiple types of parent ions.

Embodiment FIG. 1 shows an example of an apparatus for carrying out the method of the present invention. B is a magnetic field for mass analysis, E is an electric field for energy analysis, S is an ion source, D is an ion detector, and ions of a specific mass selected by magnetic field B undergo energy analysis in electric field E. There is. The metastable ions generated from the sample in the ion source undergo a cleavage reaction at a constant reaction rate from the time they are generated, but in the MIKES method, the magnetic field B and electric field E
Daughter ions generated by cleavage on the ion orbit between the two are energy-analyzed in the electric field E. In the figure, A is an ion accelerating voltage power supply, K is an electric field voltage power supply that applies to the electric field E, and the output voltage of each is determined by the microcomputer.
Controlled by CPU.

FIG. 2 is a time chart of the operation of the apparatus when carrying out an example of the method of the present invention. In this example, double daughter ion measurements are performed for each of the two parent ions. The operation is periodic, and C in FIG. 2 indicates the cycle number of the operation. B indicates a magnetic field and is set to a constant value. A is switched every cycle by the ion accelerating voltage, and takes two high and low values of Va and Va'. E indicates the electric field voltage, which can be switched to four levels of voltage, with two cycles as one period. Now the strength of the magnetic field B is the mass at the ion acceleration voltage Va
Assuming that the ion of Mp is set to pass through the magnetic field along the orbit Ob in FIG. 1, let Mp be the parent ion of one of the samples. Let Mp' = Mp + △ be the parent ion for the internal standard. The internal standard is the H of the sample molecule.
Use something similar to that in which deuterium is substituted. Therefore, the ion acceleration voltage is switched to Va and Va', and Va' is set so that the ions of Mp' pass through the magnetic field B at the ion acceleration voltage Va' and the magnetic field strength B. Therefore, it is given by Va′=Va/1+△/Mp. The masses of the two parent ions differ by the amount of deuterium substituted, and the daughter ions to be detected also differ in mass by the amount of deuterium substituted. Let the masses of ions be Md1 and Md2, and the masses of daughter ions from the internal standard parent ion be Md1' and Md2'. Second
Cycle numbers 1, 3 in the time chart shown...
(odd number) is the sample parent ion daughter ion measurement cycle;
Cycles with even cycle numbers are daughter ion measurement cycles of the internal standard parent ion, electric field voltages Ed1 and Ed2 for detecting daughter ions of the sample parent ion, daughter ions Md1' and Md2' of the internal standard parent ion, and The electric field voltages are Ed1' and Ed2'. It is given by /1+△/Mp. Here, Eo is used as a normal double convergence mass spectrometer, when ions of mass Mp that have passed through magnetic field B under ion acceleration voltage Va are detected when they pass through electric field E. is the electric field voltage of

In the above embodiment, two types of daughter ions are detected for each of two types of parent ions, and the mass spectra of both daughter ions are detected by continuously sweeping the voltage of the electric field E in a sawtooth waveform every operation cycle. It is also possible to record. Further, in the above embodiment, energy scanning is performed once while one type of parent ion is selected, but energy scanning may be repeated two or more times for one type of parent ion.

Furthermore, the above explanation was made regarding the measurement of daughter ions due to spontaneous cleavage of metastable ions, but collisional activation involves colliding a neutral molecule with a parent ion and activating the parent ion by the collision to forcefully cleave it. It can also be applied to the measurement of cleavage ions by the method. in this case,
The collision chamber is installed on the ion trajectory between the magnetic field and the electric field so that the ions can pass along the trajectory.

Effects The method of the present invention has the above-described configuration, and can measure daughter ions generated from multiple parent ions for each parent ion, almost simultaneously, and is useful in analyzing samples that change over time. By using one of multiple types of parent ions as an internal standard, it is possible to perform quantitative measurements between each daughter ion, and in this respect as well, it can provide analytically useful information. can.

[Brief explanation of drawings]

FIG. 1 is a plan view of an example of an apparatus for implementing the method of the present invention, and FIG. 2 is a time chart illustrating the operation of an example of the method of the present invention.

Claims (1)

[Claims] 1 Using a device equipped with a mass spectrometer and an energy analyzer that performs energy analysis on the ions that have passed through the mass spectrometer, ions of a constant mass pass through the mass spectrometer under one ion accelerating voltage. The cleavage ion is characterized in that the mass spectrometer is set as shown in FIG. Measuring method.