JPS5816595B2 - mass spectrometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mass spectrometer, and more particularly to a mass spectrometer equipped with an ion detection device suitable for obtaining the sum of mass spectrum intensities in any mass number range from time to time.

In other words, the sum of the mass spectral intensities referred to above refers to total ions (Total Ion), and conventionally, these total ions have been obtained by a completely different method.

That is, a mass spectrum is a signal after ions have undergone mass dispersion, whereas in the past, all ions were captured at a stage before mass dispersion occurred.

For this reason, in the case of chemical ionization measurements, etc., ions of reaction gases that are unnecessary for the measurement are also received, and since there are many fluctuations in these unnecessary parts, this causes a deterioration of the signal-to-noise ratio.

As a method to improve this, the mass spectrum is digitally converted and stored in memory, and the mass number range excluding unnecessary mass numbers such as mass numbers due to reaction gas (usually about 0 to 70) is It is conceivable to read out the mass spectra, add them digitally, and record the added values as a function of time in the form of an analog quantity on a recorder to obtain a chromatogram.

However, to carry out such a method, a computer with a large storage capacity is required, and if high-speed mass scanning is desired, the computer must have high-speed processing power to respond to it. It won't happen.

Therefore, it is inevitable that the entire device becomes extremely expensive.

Therefore, an object of the present invention is to provide a mass spectrometer that can select a mass spectrum in a mass number range excluding unnecessary mass numbers and obtain a chromatogram from the mass spectrum in an analog manner.

In other words, an object of the present invention is to provide a mass spectrometer that can momentarily obtain the sum of mass spectral intensities in an arbitrarily selected mass number range by integrating the mass spectral intensities.

The present invention is characterized in that it is possible to measure the amount of total ions corresponding to the mass number components of only the necessary portions without requiring a special total ion monitor.

Therefore, in the present invention, the objective is achieved by scanning the magnetic field or accelerating voltage at high speed and integrating the mass spectrum obtained during the scanning over a mass number range selected by a mass number selection device.

Furthermore, in order to obtain data that is easier to view, the integrator output is held from the end of one integration until the end of the next integration.

FIG. 1 shows one embodiment of the invention.

A sample introduced from a sample introduction system 1 is ionized in an ionization chamber 2, deflected and dispersed by a deflection magnetic field 3, and then captured and detected by an ion detector 4 for each mass number.

5 is a magnetic field/acceleration control device that controls the strength of the ion acceleration voltage and/or deflection magnetic field supplied to the ionization chamber 2;
7 is a device for selecting the mass number of the ion detector output that is input to the integration/hold circuit 8, and 7 is a synchronization signal generator.

In the following, the case of performing magnetic field scanning will be described. The deflection magnetic field 3 is repeatedly scanned by the magnetic field/acceleration control device 5, and the mass spectrum of the ion detector 4 obtained at this time is transmitted to the integration/hold circuit 8 at each repetition period. The integral is held by

The control signal for the integration/hold circuit 8 for this purpose is determined by the synchronization signal generator 7 and the mass number selection device 6 based on the magnetic field repetition signal.

2 and 3 are block diagrams showing an example of the configuration of the integral hold circuit and its control signals, and FIG. 4 shows signals of various parts obtained by the present invention.

The sample introduced from the sample introduction system 1 is ionized in the ionization chamber 2, but at this time all the ions leaving the ionization chamber are
It exhibits a signal as shown in Figure a.

Now, suppose that a deflection magnetic field is formed by the magnetic field scanning signal and repeated scanning is performed, then at time t1. t2. t3
The output signal obtained by the ion detector 4 is as shown in figure b.

At this time, the switch S1 is closed for a time corresponding to the range selected by the mass number selection device 6, that is, the mass number range from ml to m2 (FIG. 3A), and the output V1 of the ion detector is supplied to the integrator 81. , by integrating this, outputs 0□ to 03 of v2 in FIG. 4 are obtained for each scan.

After each integration period ends, switch S3 is closed and the integrator output V
2 and supplies it to the hold amplifier 82 to obtain v3 at its output.

Thereafter, the switch S3 is opened to hold the output v3 until the next sampling period, and the switch S2 is closed to reset the integrator 81.

As a result, the output v3 of the integrating/holding circuit 8 becomes as shown in FIG. 4 v3, which yields the total amount of ions in the range of mass numbers m1 to m2.

In this way, according to the present invention, the total ion amount can be reduced by the output
3 is a continuous step wave, so it is much easier to see than when the integral value is not held.

Further, by smoothing the output v3, a chromatogram of all ions corresponding to FIG. 4a can be obtained.

In order to make it easier to understand the relationship between the mass number selection range and the opening and closing of the switches 81 to S3, the relationship is shown in FIG.

In other words, according to the present invention, when performing measurements by directly connecting a chemical ionization method or a gas chromatograph, it is possible to eliminate the influence of fluctuations in the mass number of ions in unnecessary parts such as carrier gas and reaction gas, thereby reducing signal-to-noise. A total ion monitor with improved ratio can be realized.

Furthermore, there is no need for a separate total ion monitor device, which is effective in reducing costs.

Note that the above explanation was made assuming that the period of repeated scanning of the magnetic field or ion accelerating voltage was constant.
In reality, the period may be different.

In other words, when simply observing the mass spectrum obtained by the ion detector 4, the scanning speed is set as fast as possible (thus, the repetition period becomes short), while when recording this as data, one cycle in the middle is used. The scanning speed may be controlled to be slow only during this period.

If the scanning speed is high, the output level of the ion detector 4 decreases due to a decrease in the responsiveness of the ion detector 4 and a decrease in the amount of ions.

Therefore, if the integration and recording are carried out at this stage, an accurate romatogram will not be obtained.

In order to improve this, it is necessary to synchronize with the repetition period of the magnetic field or ion accelerating voltage, and the shorter the period, the gain of the ion detector system (the gain from the ion detector 4 to the output of the integration/hold circuit 8). It is sufficient to add a device 9 for controlling the angle to increase as shown by the dotted line in FIG.

[BRIEF DESCRIPTION OF THE DRAWINGS] Fig. 1 is a block diagram showing one embodiment of the present invention, Fig. 2 is a detailed block diagram of the integration/hold circuit shown in Fig. 1, and Figs. 3 and 4 are the apparatus of the present invention. FIG. 3 is a waveform diagram of each part for explaining the operation of the FIG. 1... Sample introduction system, 2... Ionization chamber, 3... Deflection magnetic field, 4... Ion detector, 5... Magnetic field Acceleration control system, 6...Mass number selection device, 1...Synchronization signal generator, 8...
...Integrator/hold circuit, 81...Four types separator, 82
...Hold circuit.

Claims (1)

[Claims] 1 A device that repeatedly scans an ion accelerating voltage or deflection magnetic field in a mass spectrometer that obtains a mass spectrum by ionizing the introduced sample, dispersing the resulting ions, and detecting the dispersed ions with an ion detector. a mass number selection device for selecting an ion detector output corresponding to a desired mass number range; an integrating circuit for integrating the ion detector output for the selected mass number range for each cycle of repeated scanning; A mass spectrometer comprising: a hold circuit that holds an output of an integral circuit for each period.