JPH10283983A - Mass spectrograph - Google Patents

Abstract

PROBLEM TO BE SOLVED: To recover a single spectrum from mixed spectra so as to enhance detection efficiency by inputting a spectrum signal detected through plural outlet slits and a spectrograph function deforming the spectrum so as to obtain a single slit spectrum by a deconvolution operation. SOLUTION: A magnetic field type mass spectrograph is composed of an ion source 1, an inlet slit 2, a spectrograph magnet 3, outlet slits 4, and an ion detector 5. In order to detect a mass spectrum using the same, the intensity of the analysis magnet 3 is changed so as to obtain the relationship between ion intensity detected by the ion detector 5 through the outlet slits 4 and magnetic field intensity. By operating a signal detected through the outlet slits 4, which are set to be two or more, and a device function expressing a spectrum variable which is previously measured and is recorded in a device function recorder 6 by a deconvolution operator 7, one slit single spectrum output is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic field type mass spectrometer and the like, and more particularly to a mass spectrometer for improving detection efficiency.

[0002]

FIG. 3 schematically shows a magnetic field type mass spectrometer. An ion source 1, an inlet slit 2, an analysis magnet 3, an outlet slit 4,
It is composed of an ion detector 5. Usually, to detect a mass spectrum, the intensity of the analysis magnet 3 is changed, and the relationship between the ion intensity detected by the ion detector 5 through the exit slit 4 and the magnetic field intensity is obtained. At this time, the ion detector 5
Are only a small part of the ions passing through the exit slit 4, most of them are wasted, and the detection efficiency is low.

On the other hand, as shown in FIG. 4, when the number of outlet slits 4 is two or more, the amount of ions that can be detected by the ion detector 5 increases, but the obtained mass spectrum is a mixture of a plurality of spectra. It is useless as it is. That is, the spectrum to be detected through one of the slits 4 ₁ Fig. 4 (a) (solid line), spectrum diagram is detected through the other slit 4 ₂ 4 (c)
If it were (broken line), the actually detected spectrum would be as shown in FIG. 4B in which these spectra were mixed, and would not be usable for mass spectrometry as it was.

[0004] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a mass spectrometer capable of recovering a single spectrum from the mixed spectrum and improving the detection efficiency. Aim.

[0005]

According to the present invention, there is provided an arithmetic unit for performing a deconvolution operation by inputting a spectrum signal detected through a plurality of exit slits and an analyzer function for modifying a spectrum, and performing a deconvolution operation. The spectrum of the single slit is obtained by the following. Further, the present invention is characterized in that the arithmetic unit performs the deconvolution by a Fourier transform method. Further, the present invention is characterized in that the same measurement is performed using detectors having different arrangements of exit slits, and a weighted average of Fourier transform of a spectrum obtained by performing Fourier transform is obtained.

[0006]

Embodiments of the present invention will be described below. First, the principle of the present invention will be described. In general,
The spectrum y (t) output from the detector is the convolution integral of the original spectrum x (t) and the response (device function) h (t, τ) of the analyzer that transforms the original spectrum. It is represented by Here, in the case of a mass spectrometer, y (t) is an ion current, and t is a variable represented by mass or a function of mass.

Although h (t, τ) generally relates to t, it can be considered that t (t, τ) is not related to t as long as t is narrow. Further, in the case of a magnetic field type mass spectrometer, h (t, τ) becomes independent of t by setting t = alog (m / z) (2). Here, a is an arbitrary constant, m is mass, and z is electric charge. Therefore, hereafter, h (t, τ) = h (τ) (3) Here, equation (1) can be rewritten as follows.

[0008] FIG. 1 shows these functions x (t) (FIG. 1 (a)) and y (t)
(FIG. 1 (b)) and h (t) (FIG. 1 (c)), where the original spectrum x (t) is a thin line, but the characteristic h (τ) of the device is Since the spectrum y (t) has a spread, the spectrum y (t) detected by being deformed has a spread.

Next, let y (t) be the output in the case of one exit slit, and let w (t) be the output in the case of two exit slits. Here, for the sake of simplicity, it is assumed that the device function of a single output from each slit is equal, It can be expressed as. t ₁ and t ₂ represent the deviation of the slit position. Also, w (t) is Can also be expressed as In any case, w (t) is y
(T) or x (t) and the newly defined device function h _w
(Τ) or convolution integral with hs (τ). Here, h _w (τ) or hs (τ) is a measurable function. Therefore, w (t) and h
_{If w} (τ) or hs (τ) can be measured, equation (5) or equation (6) can be solved to find y (t) or x (t). A method of solving this convolution integral in reverse is known as deconvolution, and various methods are known, and any of those methods may be used (for example, “waveform data for scientific measurement”). Processing "South
Edited by Shigeo, Q Publishing 1986).

The above is the principle of the present invention. Implementation of the present invention requires that h _w (τ) or hs (τ) be determined separately from the actual spectral measurement, deconvolution of the convolution integral, and implementation of multiple exit slits .

In the above processing, it takes time to calculate the deconvolution. However, the deconvolution method using the Fourier transform is advantageous because a fast Fourier transform (FFT) technique can be used. here, Then, taking the Fourier transform of both sides of the above equation, Becomes Therefore, the Fourier transform Y (ω) of the signal y (t) is obtained as Y (ω) = W (ω) / H _w (ω) (8) Next, if the inverse Fourier transform of Y (ω) is obtained, y
(T) is obtained. This is the principle of deconvolution by Fourier transform.

However, in equation (8), | H _w (ω) | = 0
And the signal may not be completely recovered. Next, another example of the present invention which avoids this difficulty will be described. For this purpose, two sets of slits having different arrangement patterns of a plurality of slits are prepared, and spectrum measurement is performed using each of them. At this time, each device function is represented by h ′
_w , h ″ _w . These Fourier transforms H ′
It is assumed that the zero points of _w (ω) and H ″ _w (ω) are arranged in a slit such that they do not overlap each other. From the outputs W ′ (t) and W ″ (t) obtained from the respective slits and their Fourier transforms, The Fourier transform of the signal is as follows: Y ′ (ω) = W ′ (ω) / H ′ (ω) (9) Y ″ (ω) = W ″ (ω) / H ″ (ω) (10) Here, as a final result, equation (9) is obtained.
And the weighted average of equation (10).

[0013] Here, D ′ (ω) and D ″ (ω) are smooth functions,
D ′ (ω) becomes 0 at the zero point of H ′ (ω), and D ″ (ω)
(Ω) is assumed to be 0 at the zero point of H ″ (ω). Briefly, D ′ (ω) = | H ′ (ω) | ² (12) D ″ (ω) = | H ″ (ω) | ² (13) Equations (12) and (13) are smooth functions except for each zero point. Y (ω) is not affected by the zero point of H (ω),
More complete signal recovery can be achieved.

The present invention can be modified in various ways.
In equation (5), two slits are used, but three or more slits can be used. In addition, in order to determine the apparatus function, the spectrum may be measured using a sample showing a simple spectrum (preferably, a single peak spectrum). If that is not possible, one of the slits
It can be obtained by leaving a single unit and providing a mechanism to block other slits, and performing spectrum measurement on each slit. In the above description, a method of restoring y (t) has been described, but it is of course possible to restore x (t).

FIG. 2 is a schematic diagram showing the configuration of an apparatus for carrying out the present invention. The ion source 1, the entrance slit 2, the analysis magnet 3, the exit slit 4, and the ion detector 5 are the same as those of the apparatus shown in FIG. 3, but the slit 4 is composed of two pieces. The detected signal is measured in advance w (t), and the device function recorder 6
The device function representing the deformation of the spectrum recorded in
(Τ) Assuming that the output of one slit alone is y (t), w (t), h (τ) and y (t) have the relationship shown in equation (5). By solving the equation (5), the spectral output y (t) of one slit alone is obtained. Of course, the set of slits is 2
The number is not limited to three, and may be three or more.

[0016]

As described above, according to the present invention, a plurality of exit slits can be used, so that many signals can be taken in, the detection sensitivity can be improved, and a plurality of exit slits can be used. By performing the measurement using the multiple exit slits, the effect of the zero point of the Fourier-transformed device function can be reduced, and the deformation of the recovered spectrum can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining spectrum deformation by a device function.

FIG. 2 is a diagram showing an example of a device configuration of the present invention.

FIG. 3 is a diagram schematically showing a magnetic field type mass spectrometer.

FIG. 4 is a diagram showing a spectrum when there are two exit slits.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Ion source, 2 ... Entrance slit, 3 ... Analysis magnet, 4
... exit slit, 5 ... ion detector, 6 ... device function recorder, 7 ... deconvolution calculator.

Claims (3)

[Claims] 1. An arithmetic unit for inputting a spectrum signal detected through a plurality of exit slits and an analyzer function for transforming a spectrum and performing a deconvolution operation, wherein a spectrum of a single slit is obtained by a deconvolution operation. A mass spectrometer characterized in that: 2. The mass spectrometer according to claim 1, wherein the arithmetic unit performs the deconvolution by a Fourier transform method. 3. The apparatus according to claim 2, wherein the same measurement is performed using detectors having different arrangements of the exit slits.
A mass spectrometer characterized by taking a weighted average of a Fourier transform of a spectrum obtained by performing a Fourier transform.