JPH08124519A - Data processing device for mass spectrometer/mass spectroscope - Google Patents

Abstract

PURPOSE: To facilitate fixing of a parent ion by determining the candidates thereof by making reference to the database of structure establishing rules storing rules for establishing the parent ion from each type of daughter ion and detached group. CONSTITUTION: A peak analysis section extracts peak ion candidates and detached group candidates regarding all peaks, and the data of the extraction is sent to a parent ion estimation section. In addition, a parent ion estimation section first prepares the combinations of daughter ions and detached groups likely to become mass, on the basis of the data of mass spectra, and ion and leaving group candidates. Thereafter, the estimation section calculates the possibility of the combinations, referring to rules in the database of structure establishing rules, regarding each of possible combinations. Also, the estimation section estimates the structure of parent ions according to the order of high probability by referring to the peak height of mass spectra. Finally, parent ion candidates resulting from the estimation are shown on a display in the order of high probability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data processor for analyzing data obtained by an MS / MS mass spectrometer. The MS / MS mass spectrometer is used mainly in the fields of medicines, foods, etc. in combination with a liquid and gas chromatograph for trace component analysis, or alone.

[0002]

2. Description of the Related Art An ordinary mass spectrometer only detects the total mass of an ion, but an MS / MS mass spectrometer cleaves the ion (parent ion) and a spectrum of a daughter ion generated by the cleavage is obtained. By detecting
Information about the structure of the parent ion can be obtained. This makes it easier to identify the parent ion (sample).

The MS / MS mass spectrometer has three quadrupoles arranged in series, a parent ion is selected in the first quadrupole and a parent ion selected in the second quadrupole. Is cleaved, and daughter ions generated by the cleavage are selected and detected at the third quadrupole. Therefore, the data obtained from the MS / MS mass spectrometer is the mass mp of the parent ion and the mass spectrum pattern of the daughter ion.

[0004]

In a general mass spectrometer, compound information (compound name, structure) and a mass ion number and intensity check table for a large number of compounds are prepared in advance as a data library. The compound can be identified by comparing the mass number of each peak in the spectrum with that. On the other hand, in the second stage of the MS / MS mass spectrometer, a cleavage gas is introduced into the quadrupole and the parent ion is cleaved by collision with the cleavage gas, but due to the difference in collision energy at this time, the parent ion is It cleaves in various ways. For this reason, the mass spectrum patterns (peak appearance positions and heights) of the obtained daughter ions are very diverse, and it is difficult to prepare all the patterns in such a library in advance. For this reason, conventionally,
A method has been used in which the library pattern is narrowed down to some extent based on the separately obtained information on the structure of the parent ion (sample) (for example, an amino acid sequence or the like), and matching is performed therein. However, this requires some additional information on the parent ion and is a work that requires experience, so it was not possible for anyone to easily identify the parent ion. In addition, since library data does not exist for all patterns, there are cases where identification cannot be performed.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a data processor for MS / MS mass spectrometers, which facilitates identification of parent ions. Especially.

[0006]

A data processor for an MS / MS mass spectrometer according to the present invention made to solve the above-mentioned problems selects a parent ion in a first mass filter section and a cleavage section. A data processing device for an MS / MS mass spectrometer, which cleaves the parent ion and collects the mass spectrum of the daughter ion generated by the cleavage with the second mass filter unit. A) Ions corresponding to various masses Peak database that stores species information, b) Mass of leaving group that may be released by cleavage and leaving group database that stores species information, c) Mass spectrum collected above Detect the peak from
Peak detection means for obtaining the desorbed mass by subtracting the peak mass from the peak mass and the mass of the parent ion for each peak; and d) For each peak, refer to the peak database to determine the ion species corresponding to that peak mass. Peak analysis means to extract candidates and also candidates for leaving groups corresponding to the released mass by referencing the leaving group database, and e) constructing parent ions from various daughter ions and leaving groups. By referring to the structure-building rule database that stores the rules for performing the above, and f) the structure-building rule database, parent ion candidates are identified based on the mass of the parent ion, the analysis result by the peak analysis means, and the height of each peak. And a parent ion estimating means for determining.

[0007] The daughter ions forming the spectrum collected by the second mass filter section may include the parent ions themselves which have not been cleaved at the cleaving section.

[0008]

The peak detecting means detects peaks from the mass spectrum collected by the second mass filter section according to a predetermined reference, and the peak mass md of each detected peak.
And the desorption mass mr (= mp-md) obtained by subtracting the peak mass md from the mass mp of the parent ion. The peak analysis means first extracts a candidate ion (daughter ion) corresponding to the peak by collating the peak mass md with the peak database. The number of candidates may be one or may be plural. Similarly, a leaving group candidate (one or more) corresponding to the peak is extracted by matching the leaving mass mr with the leaving group database.
The peak analysis means performs such processing for all detected peaks and extracts daughter ion candidates and leaving group candidates. The parent ion estimation means determines the parent ion candidate by referring to the structure construction rule database based on the mass of the parent ion, the daughter ion candidate and the leaving group candidate, and the height of each peak. Among the many daughter ion candidates and leaving group candidates, there are combinations that cannot coexist with each other in view of the mass of the parent ion, and conversely, there are combinations of groups and daughter ions that are likely to leave with a high probability. . This information is stored in the structure construction rule database,
The parent ion estimation means determines parent ion candidates in descending order of probability.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure and operation of an MS / MS mass spectrometer using a data processor which is an embodiment of the present invention will be described with reference to FIG. A sample separated by a liquid chromatograph, a gas chromatograph, or the like, or a sample directly introduced is ionized in the ionization chamber 11. A for ionization
Any conventional ionization method such as PCI (AtomosPheric Chemical Ionization), CI (Chemical Ionization), TSP (ThermoSpray Ionization) can be used. . The ionized sample is extracted by the extraction electrode and introduced into the first-stage quadrupole 13 by the ion lens 12. A superimposed voltage of direct current and high frequency is applied to the first-stage quadrupole 13 from the first RF / DC voltage applying unit 23, and only ions (parent ions) having a predetermined mass number (m / z) mp are in the first-stage. It passes through the quadrupole 13 and enters the second stage quadrupole 15. Since the first RF / DC voltage application unit 23 operates according to the control signal from the first QP control unit 41 (FIG. 2) in the control unit 30, the mass mp of the parent ion passing through the first-stage quadrupole 13 is It is known in the control unit 30.

The second stage quadrupole 15 is housed in a container 14 (a cleavage chamber), and a cleavage gas is introduced into the cleavage chamber 14. The parent ions that have passed through the first-stage quadrupole 13 collide with the cleavage gas in the cleavage chamber 14 and are separated into daughter ions and leaving groups. There are various modes of this cleavage, and generally, the cleavage occurs at the weakest bond portion, but the cleavage also occurs at the relatively strong bond portion depending on the collision energy. Therefore,
Daughter ions of various masses are generated in the cleavage chamber 14, and these daughter ions are introduced into the third stage quadrupole 16 by the second stage quadrupole 15. The drive voltage of the second-stage quadrupole 25 is applied from the second RF / DC voltage applying section 25.

In the third stage quadrupole 16, the first stage quadrupole 13
R applied by the third RF / DC voltage applying unit 26
Only daughter ions of mass md corresponding to the F / DC superimposed voltage are passed. The daughter ions that have passed through the third-stage quadrupole 16 are detected by the detector 17, and the detection signal is transmitted to the control unit 30 via the A / D converter 27. Third Q in control unit 30
The P control unit 42 (FIG. 2) scans the mass md of the daughter ions passing through the third-stage quadrupole 16 by sequentially changing the control signal given to the third RF / DC voltage applying unit 26. Thereby, the control unit 30 obtains the mass spectrum of the daughter ions generated by the cleavage.

The control unit 30 is a computer having a CPU, a ROM, and a RAM, in which an external storage device 31,
The display 32 and the like are connected. The control unit 30 is functionally composed of a peak detection unit 43, a peak analysis unit 44, a parent ion estimation unit 45, and the like, in addition to the first and third QP control units 41 and 42. In addition, the external storage device 31
Inside, a peak database 46, a leaving group database 47, and a structure construction rule database 48 are provided. The peak database 46 stores various masses and ion species having the masses as a control table, and the leaving group database 47 stores various masses and leaving groups (usually neutral) having the masses as a control table. It was done.
In addition, the structure construction rule database contains various rules for constructing parent ions from various parts (daughter ions, leaving groups, etc.) such as possible combinations of various ions and leaving groups and their binding (or separation) energies. Is stored.

The procedure of data processing performed by the control unit 30 will be described with reference to the flowchart of FIG. First, the peak detection unit 43 creates a mass spectrum based on the detection signal from the detector 17 and the scanning signal (daughter ion mass md) from the third QP control unit 42, and detects all the peaks therein according to a predetermined standard. Yes (step S1). As a reference for peak detection at this time, for example, the point where the slope of the spectrum curve is equal to or greater than a predetermined value is the start point of the peak, and then the slope becomes zero and becomes negative, and then the absolute value is equal to or less than the predetermined value It is possible to take a method such as setting the point at which the peak is reached as the peak end point. When all peaks have been detected, the mass md of each detected peak is then detected (step S2). Further, the peak mass md is subtracted from the mass mp of the parent ion obtained from the control signal of the third QP control unit 42 to calculate the desorption mass mr (= mp-md) (step S3).

After the peak detecting section 43 detects md and mr for all the peaks by the above processing (step S
4) These data are passed to the peak analysis unit 44.
In the peak analysis unit 44, by comparing the daughter ion mass md of each peak with the data in the peak database 46, an ion (peak ion candidate) having that mass md is obtained.
Are all extracted (step S5). Also, desorption mass mr
Is compared with the data in the leaving group database 47 to extract all leaving groups (leaving group candidates) having the mass mr (step S6). In these steps, it is desirable that the detected ion mass and desorption mass have a predetermined width, and the database is searched within the range.

After the peak analysis unit 44 has extracted the peak ion candidates and the leaving group candidates for all the peaks in this way, the data are sent to the parent ion estimation unit 45.
Based on the mass spectrum data and the ion candidate and leaving group candidate data, the parent ion estimation unit 45 first determines the mass mp.
Create possible combinations of daughter ions and leaving groups.
Here, the number of daughter ions and leaving groups constituting the combination may be three or more. Then, the possibility of such a combination is calculated by referring to the rules in the structure construction rule database for each of the possible combinations. Then, by comparing with the peak height of the mass spectrum, the structures of parent ions are estimated in order of high probability (step S7). Finally, the estimated parent ion candidates, which are the estimated results, are displayed on the display 32 in descending order of probability (step S8).

[0016] As an option, the allowable width in detecting the peak top mass md of the mass spectrum and the strictness of the applicability of the structure construction rule are ranked in advance, and the analyst can select the rank in advance. You can also leave it. As a result, a large number of parent ion candidates will be output when a gentle rank is selected, and the analyst can select an appropriate one based on other information (such as information on the sampling point). become able to. On the other hand, when the strict rank is selected, only one parent ion candidate is output, and even a beginner can determine the parent ion without hesitation. Even in this case, of course, the probability of being the parent ion is the maximum, but if the absolute value of the probability is low, a message to that effect is added and output.

[0017]

In the data processor for MS / MS mass spectrometers according to the present invention, each peak is associated with a corresponding ion rather than simply judging by the entire daughter ion spectral pattern as in the conventional case. Information about the leaving group is extracted from the database, and the parent ion is identified based on the probability of the combination. Therefore, the parent ion can be identified even if the corresponding spectrum pattern does not exist in the database, and the identification can be performed without the information about the parent ion in advance. For this reason, it becomes possible to identify the sample even by an unskilled person as in the conventional case.

[Brief description of drawings]

FIG. 1 is an M with a data processing device according to an embodiment of the present invention.
The schematic block diagram of a S / MS mass spectrometer.

FIG. 2 is a block diagram showing a functional configuration of a control unit.

FIG. 3 is a flowchart showing a procedure of data processing performed by a control unit.

[Explanation of symbols]

 11 ... Ionization chamber 12 ... Ion lens 13 ... 1st stage quadrupole 14 ... Cleavage chamber 15 ... 2nd stage quadrupole 16 ... 3rd stage quadrupole 17 ... Detector 23, 25, 26 ... RF / DC voltage Application unit 27 ... A / D converter 30 ... Control unit 31 ... External storage device 32 ... Display

Claims (1)

[Claims] 1. MS / MS mass spectrometry in which a parent ion is selected in the first mass filter unit, the parent ion is cleaved in the cleavage unit, and a mass spectrum of daughter ions generated by the cleavage is collected in the second mass filter unit. A data processing device for a device, comprising: a) a peak database that stores information on ion species corresponding to various masses; and b) masses of leaving groups and leaving groups that may be eliminated by cleavage. A leaving group database containing species information, and c) detecting peaks from the collected mass spectrum,
Peak detection means for obtaining the desorbed mass by subtracting the peak mass from the peak mass and the mass of the parent ion for each peak; and d) For each peak, refer to the peak database to determine the ion species corresponding to that peak mass. Peak analysis means to extract candidates and also candidates for leaving groups corresponding to the released mass by referencing the leaving group database, and e) constructing parent ions from various daughter ions and leaving groups. By referring to the structure-building rule database that stores the rules for performing the above, and f) the structure-building rule database, parent ion candidates are identified based on the mass of the parent ion, the analysis result by the peak analysis means, and the height of each peak. A data processing apparatus for MS / MS mass spectrometer, comprising: a parent ion estimating unit for determining.