JPH10125278A - Ion trap type mass spectrometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine the proper ionization time for obtaining a sufficient ion quantity with no saturation by applying a fixed signal to the trap field, and excluding the ions other than the aimed peak ions. SOLUTION: The ions ionized by an ionizing device 1 are guided by a guide signal generator 2 to the trap field 3 formed by an RF signal generator (RF)4 and trapped. A signal is applied here by an FF signal generator 5, and the ions other than the ions in the necessary mass range are excluded. The signal applied to the trap field 3 is scanned by the RF 4, and the aimed peak derived ions are discharged from the trap field 3. The ions are detected by an ion detector 6 to obtain a mass spectrum. The timing of these signals is controlled by a control device 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an ion trap mass spectrometer.

[0002]

2. Description of the Related Art In an ion trap mass spectrometer, an ionized sample is introduced and trapped in a trapping field formed by applying a constant signal. If the intensity of the signal applied to the trapping field is changed in this state, only ions having a specific mass number corresponding to the intensity are ejected from the trapping field. Therefore, in one-stage mass analysis (MS), this signal is By scanning in an arbitrary range, a mass spectrum in a corresponding mass range is obtained. In two or more stages of mass spectrometry (MS / MS), ions in a certain mass range are introduced into the trap field at the first stage. In the second stage, only the ions of the mass number of interest are left in the trap field, this ion is decomposed by applying a certain signal, and the operation of generating the derived ions is repeated as many times as necessary. In this method, a signal in which the remaining ions are applied to a trapping field is scanned to obtain a mass spectrum.

In the multi-stage measurement, ions other than the ion of the peak of interest in the second and subsequent stages are excluded from the trapping field. Therefore, in order to improve the intensity of the mass spectrum obtained by scanning at the end, At the time of introduction, it is necessary to introduce as many ions as possible into the trap field. However, there is a limit to the amount of ions that can be included in the trap field, and when a large amount of ions exceeding that are introduced into the trap field, the ions are saturated in the trap field, and when a certain signal is applied to the trap field. However, there is a problem that ions having the corresponding mass number obtained in the above are not discharged from the trap field, and a correct mass spectrum cannot be obtained. Therefore, from the maximum amount of ions that can be trapped in the trap field without being saturated, it is necessary to limit the time for introducing ions into the trap field according to the ionization efficiency of the sample, and to adjust the ions so that they are not saturated in the trap field. .

As one of the methods, in one-stage mass spectrometry (MS), ions are introduced into a trapping field with a small fixed introduction time immediately before a scan for acquiring data.
There is a method of performing a preliminary scan in which scanning is performed at high speed in the same mass range as a scan for acquiring data. The total amount of the ion intensity of the data obtained here is obtained, and from this value, the ion introduction time for obtaining the maximum ion amount without saturation for the scan for obtaining the data can be obtained. At this time, for data outside the specified mass range, applying a constant signal to the trap field is excluded from the trap field.

[0005]

In an ion trap type mass spectrometer, the speed of scanning a signal applied to a trap field lowers the sensitivity of the obtained mass spectrum. Therefore, scanning is performed faster than scanning for acquiring data. The sometimes obtained ion amount has an error compared to the amount obtained when scanning at the speed at the time of data acquisition. When the ion introduction time is calculated based on the data obtained here and scanning is performed, a spectrum with the maximum intensity cannot be obtained. In addition, the preliminary scan is for calculating the ion introduction time of the scan for acquiring data and does not acquire a mass spectrum, and therefore needs to be shorter in time than the scan for acquiring data.

[0006] In the mass spectrometry (MS) of only one stage, since the ions in the entire mass range are subject to the mass spectrum obtained as the measurement result, the total amount of ion intensities obtained by scanning is large. By knowing the total amount of ions obtained by high-speed scanning, it is possible to calculate the time during which ions for obtaining sufficient sensitivity can be introduced. The same means can be considered in multi-stage mass spectrometry (MS / MS). However, in multi-stage analysis, in each stage after the second stage,
Since the total amount of ion intensity decreases to eliminate all ions other than the ion of the peak of interest, introduce more ions in the first step to obtain sufficient sensitivity in the last acquired mass spectrum There is a need to.

[0007]

Means for Solving the Problems In a measurement in which multiple stages of mass spectrometry are performed, the scan range for preliminary scanning is limited to only a mass number range near a peak of interest in the second stage of mass spectrometry. By performing scanning, scanning can be performed at the same scanning speed as scanning for acquiring data in a short time. In addition, when introducing ions, a certain signal is applied to the trapping field, and ions other than those of the peak of interest are excluded, so that only the total amount of ions near the mass number of the peak of interest is obtained, and data based on this value is obtained. By calculating the ion introduction time for the scan for obtaining the above, it is possible to obtain an appropriate ion introduction time for obtaining a sufficient ion amount in the first stage without saturation.

[0008]

FIG. 1 shows the configuration of an embodiment of the present invention. The ions ionized by the ionizer 1 are introduced into the trap field 3 by the signal generator 2 for introducing ions into the trap field. At this time, a trap field is formed in the trap field 3 by a signal applied by the signal generator 4, and the introduced ions are trapped. Here, by applying a signal with the signal generator 5, only ions in a necessary mass range are limited, and other ions are excluded. Thereafter, the ion of the peak of interest is destroyed by the signal generator 4 and the signal applied to the trapping field is scanned by the signal generator 4, whereby the derivative ion of the peak of interest is discharged from the trapping field. These ions are detected by the ion detecting means 6, and a mass spectrum is obtained. Further, the timing of these signals is controlled by the control device 7.

FIG. 2 shows a time chart of an ion introduction signal, an RF signal, and an FF signal in the embodiment of the present invention. When performing mass spectrometry in a plurality of stages, the ion introduction 4 is performed in a trap field for a certain short time before scanning for acquiring data. At this time, by applying a constant signal 5 to the trap field by the FF signal generator, only ions near the mass number of the peak of interest enter the trap field. Then, the signal 6 is applied and scanned by the RF signal generator only in the range near the mass number of the peak of interest. The ions emitted by this scan are detected by a detection device,
Based on the total amount of the obtained ions, the ion introduction time is determined so that the ions are not saturated in the trapping field, and ion introduction 7 for acquiring data is performed in accordance therewith. At this time, similarly to the ion introduction 4, a constant signal 8 is applied to the trapping field by the FF signal generator so that only ions near the mass number of the peak of interest enter the trapping field. Thereafter, by applying the signal 6 by the RF signal generator and the signal 10 by the FF signal generator, ions other than the peak ion of interest are ejected from the trapping field. Thereafter, by applying a constant signal 11 by the FF signal generator, the ion of the peak of interest is destroyed, and a derivative ion of this ion is generated in the trap field. This operation is repeated as many times as necessary, and finally the ions remaining in the trapping field are scanned by applying the signal 12 to the trapping field by the RF signal generator. At this time, a mass spectrum is obtained by detecting the ejected ions with a detection device.

[0010]

According to the present invention, a multi-stage mass spectrometry (MS)
/ MS), an appropriate ionization time for obtaining a sufficient ion amount without saturation can be determined.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the device of the present invention.

FIG. 2 is a timing chart of an embodiment of the device of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ionization apparatus, 2 ... Introduction signal generator, 3 ... Trap field, 4 ... RF signal generator, 5 ... FF signal generator,
6 ... Ion detection device, 7 ... Control device.

Claims (1)

[Claims] An ionization means for ionizing a sample; an introduction means for introducing ions to a trapping field; a trapping field for trapping the ions; a means for discharging the ions trapped in the trapping field; In an ion trap type mass spectrometer having a means for detecting the amount of ions discharged from the trapping field, a measuring device for performing a plurality of stages of mass spectrometry has a means for appropriately determining an ion introduction time at the time of measurement. Characteristic ion trap type mass spectrometer.