JPS60138453A - Mass spectrometer - Google Patents

Abstract

PURPOSE:To eliminate remaining gas noises and off set noise components and to obtain a highly precise mass spectrometric value by deducting a detected ion current when the gas introduction to an analyzer main body is obstructed from the ion current during the gas exhaustion. CONSTITUTION:The gas introduction to the analyzer main body 4 is obstructed by intercepting a valve 11 by a controlling part 18, a switch circuit 16 is changed over to an offset hold circuit 14 side to detect the ion current under this state, and the valve is held by the circuit 14. The ion current corresponds to the remaining gas component in the body 4 and the offset level in an amplifier 12. Next, the valve 11 is opened, a calibrating gas is introduced to the body 4, and the ion current at the time is held in a sensitivity holding circuit 15. A three way valve 3 is changed over to the analyzing sample gas side to introduce said gas to the body 4, and the ion current is detected from the detected value, the detected value during obstructing the gas introduction is deducted. Further a detecting sensitivity coefficient is multiplied to said value to obtain the analyzed result without noises.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a mass spectrometer capable of performing highly accurate mass spectrometry.

[Technical background of the invention and its problems]

Recently, there has been an increasing need to continuously measure the concentration of various gas components over a long period of time.

For example, in the field of industrial technology, it plays a major role in surface analysis of semiconductor materials and component analysis of ambient gas, and in the medical field, it is used to monitor metabolic functions by measuring the concentration of respiratory gas components of patients immediately after surgery. , its importance is recognized.

To perform such measurements, a mass spectrometer as shown in FIG. 1 has conventionally been used.

This mass spectrometer selectively supplies a sample gas introduced through an introduction tube 1 or a calibration gas given from a container 2 to an analyzer main body 4 via a three-way valve 3, and outputs the analyzer main body 4. It has a configuration in which detection is performed via a processing circuit 5. The apparatus main body 4 includes an ion source 6 that ionizes the introduced gas by thermionic bombardment, an analysis tube 7 in which the ion beam is injected, and a magnetic field that deflects the ion beam according to the mass-to-charge ratio (rye) of the ions. Formed magnet part 8
, and one or multiple collectors 9 for detecting the deflected and separated ions.

According to this device, the ion beam generated by ionizing the introduced gas is separated into its components according to the -v'e. It becomes possible to effectively perform mass spectrometry of the introduced gas.

By the way, when the above-mentioned apparatus is operated for a long time, the ionization efficiency of the ion source 6 and the amplification sensitivity of the processing circuit 5 tend to fluctuate over time. Therefore, for example, every time a predetermined period of time elapses, the three-way valve 3 is completely replaced, a calibration gas of a known concentration is introduced from the Genpe 2 instead of the sample gas, and similar ion current detection is performed. Calibration of the ionization efficiency, amplification sensitivity, etc. is performed. However, with only such a calibration method, it has not been possible to calibrate the adverse effects of the residual gas components in the analysis tube 7 and the offset of the amplifier in the processing circuit 5. Finally, even if we calculate the ion current of a calibration gas with a known concentration, we can only obtain the relationship between its consistency and ion current, so it is difficult to calculate the effects of residual gas components and sensitivity changes due to offset, etc. as mentioned above. As a result, it was not possible to improve the detection accuracy in areas other than the vicinity of the known f degrees.

[Purpose of the invention]

The present invention was developed in light of these circumstances, and its purpose is to provide a highly practical mass spectrometer that eliminates residual gas noise, offset noise, etc., and enables mass spectrometry with a high degree of roughness at all times. We will provide the equipment.

[Summary of the invention]

The present invention provides a means for preventing the introduction of gas into the analyzer main body, and a means for holding the detected ion current by the analyzer main body when gas introduction is blocked, so that the ion current detected when the gas is introduced into the analyzer main body is provided. The retained detection ion current is subtracted from the ion current, and the mass spectrometry value r of the human gas is obtained using the subtracted output.

〔Effect of the invention〕

Thus, according to the present invention, the detected ion current in a state where no gas is introduced is held, and mass spectrometry is performed by subtracting this from the detected ion current when gas is introduced. It becomes possible to increase the flow of ions to the gas. Then, sensitivity calibration is performed using a calibration gas for the ion current determined in this manner, so that highly accurate mass spectrometry can be performed over the entire dynamic range of both legs of the apparatus main body. In addition, by performing the above calibration process, for example, at predetermined intervals, it is possible to sequentially calibrate fluctuations in residual gas noise and offset noise, and it is possible to perform highly accurate measurements over a long period of time. Great effects can be achieved.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a schematic configuration diagram of an embodiment of powder loading), and the same parts as those of the conventional device shown in FIG. 1 are denoted by the same reference numerals.

This cylinder is 09. This is because a valve 1 is provided between the three-way valve 3 that selectively makes the sample gas and the calibration gas equal in size and the analyzer main body 4, and the gas introduction to the analyzer main body 4 is shut off (on). - Off control), and the processing circuit 5 is configured as follows.

The processing circuit 5 includes a preamplifier 12 that amplifies the flow of ions detected by the collector 9, a switch circuit that selectively outputs the amplified output to a subtracter 13, an offset hold circuit 14, a sensitivity hold circuit 15, and a sensitivity correction circuit. It is constructed with a coefficient unit 17 for performing the following. Also control s78
The three sides 4f3, the valve 1, and the switch circuit 16 are operated in conjunction with each other to perform switching control, and to calibrate the detection accuracy for the main body 4.

Therefore, when the control unit 18 shuts off the valve 11 to prevent gas from being introduced into the analyzer main body 4, the control unit 18 switches the switch circuit flow to the offset hold circuit 14 side, and controls the main body of the analyzer when gas control is not performed. 4 (cathode 9) is given to the offset hold circuit 14. The ion current detected in this state corresponds to the residual gas component in the apparatus main body 4 and the offset level in the amplifier 2, and the offset hold circuit J4 samples and holds this. The information on the ion current held in the offset hold circuit 14 is updated each time the gas introduction prevention control is performed.

Also, open valve 1 and pass through three-way valve 3? When a calibration gas of known magnetism is introduced from the sample 2 to the analyzer main body 4, the switch circuit 16 is switched to the sensitivity hold circuit 16 side. Then, the ion current detected at this time is sampled and held in the sensitivity hold circuit J5.

When the analysis sample gas is introduced into the analyzer main body 4 through the three-way valve 3, the ion current detected from the cathode 9 is applied to the subtracter 13 through the switch circuit.

Then, in this subtracter 13, the ion current value held in the offset hold circuit 14 is subtracted from the detected ion current, and the subtracted value is then applied to a coefficient unit 17. This coefficient multiplier 14 determines the characteristic for detection sensitivity from the information held in the two hold circuits 14 and 15, and multiplies the output of the subtractor 3 by using this as a coefficient.

This makes it possible to obtain analysis results in which the effects of residual gas noise and the like are removed from the output of the coefficient unit Noah.

That is, the ion current value detected in the state where the introduction of gas is blocked and held in the offset hold circuit 4 is now set to 0. This ion current value I.

Since this is a state in which no gas is introduced, it can be said that the residual inside the analyzer main body 4 is caused by a gas component, an offset component of the amplifier 12, or the like. On the other hand, the ion current value I held in the sensitivity hold circuit 15 when the calibration gas is introduced can be said to be a detected value for the known temperature Pr obtained by the apparatus main body A. Therefore, from these two pieces of information, the detection sensitivity percentage (coefficient) K of the device main body 4 can be determined as Po =Q. This coefficient indicates the operating characteristics of the device I'I-main body 4, and the coefficient multiplier 12 uses this coefficient. In the Chain 3 diagram, characteristic a indicates the coefficient K determined in this way.

On the other hand, the ion current generated when the analysis sample gas is introduced contains components (ion current IO) caused by the above-mentioned residual gas, etc. Therefore, the ion current I, which is inherent to the analysis sample gas, is 1t==i-i.

It can be shown as Therefore, the subtracter 13 subtracts the offset component held in the offset hold circuit 14 from the detected ion current (2). It is possible to obtain ingredients that have removed the harmful effects of the gas tank. Then, if this detected value is subjected to coefficient processing by the coefficient unit 17,
As shown in the characteristics in FIG. 3, it is possible to remove 16 offsets and to perform concentration detection under conditions that match the characteristics of the main body 4 of the apparatus.

By the way, conventionally, when the gas introduction is blocked, calibration is performed with the temperature 0 and the ion current 0, based only on the information of the ion current value I found when introducing the calibration gas and the known concentration P at that time. Therefore, the calibrated sensitivity is as shown in characteristic C in FIG. For this reason,
Detection accuracy is only improved in the vicinity of the above-mentioned calibration quality point in a state where residual gas components are included. In this regard, in this device, the detection sensitivity of the device main body 4 is adjusted to the characteristic a in Fig. 3 after taking into account the offset of residual gas components, etc.
After making the settings as shown in the figure, the offset component is subtracted and the detection sensitivity is set as shown in the figure to perform mass spectrometry. It is possible to perform highly accurate detection over the entire dynamic range.

The calibration process by switching the valves 3 and 1 and the switch circuit 16 may be performed at predetermined time intervals under the control of the control cylinder Sys, but it may also be performed at appropriate times by manually switching the valves 3 and 1 and the switch circuit 16. good. In addition, the present invention can be implemented with modifications without departing from the gist thereof.

[Brief explanation of drawings]

FIG. 1 is a basic configuration diagram of a mass spectrometer, FIG. 2 is a schematic diagram of an embodiment of the device of the present invention, and FIG. 3 is a characteristic diagram for explaining the calibration operation of the embodiment device. No...introduction tube, 2...? 3... Three-way valve, 4... Analyzer main body, 5... Processing circuit, 1...
...Valve, 12...Preamplifier, 13...Subtractor, 1
4...offset hold circuit, 5...sensitivity hold circuit, 16...switch circuit, 17...coefficient unit.

Claims (1)

[Claims] An analyzer main body that ionizes an introduced gas and detects its ion current, a means for selectively introducing an analysis sample gas and a calibration gas, and a supply of this selectively introduced gas to the analyzer main body. a means for holding the detected ion current of the analyzer main body when the gas introduction is shut off by the valve; and means for holding the detected ion current of the analyzer main body when the selected gas is supplied to the analyzer main body. A mass spectrometer comprising means for subtracting and outputting a detected ion current.