JPH10247471A - Mass spectrometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To rapidly discharge undesired components which remains in an ionization chamber after adjusting parameters. SOLUTION: A bypass channel 26 is provided in a vacuum housing 10 from a channel connected to an ionization chamber 11 by way of a valve 25. After a standard sample gas is introduced, valves 23 and 24 are closed before the valve 25 is opened. Therefore, the standard sample gas left in the channel between the valves 23 and 24 and the ionization chamber 11 is rapidly discharged through the bypass channel 26. Then, the analysis of a target sample can be quickly initiated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mass spectrometer, and more particularly, to a mass spectrometer provided with an ion source for performing ionization by a chemical ionization method.

[0002]

2. Description of the Related Art In a mass spectrometer, gaseous sample molecules are ionized by an ion source, and the ions are converted into a mass number (mass m / m).
It has a configuration in which detection is performed separately according to the number of charges z). Various methods, such as an electron impact method and a surface ionization method, are used for ionizing a sample molecule. Chemical ionization (CI = Chemical Ioniz)
), a reaction gas such as methane or isobutane is introduced into the ionization chamber, and bombards the electrons with a collision with an electron flow or corona discharge or the like to strike out specific ions (for example,
⁺ CH ₅ , ⁺ (CH ₃ ) ₃ C, etc.). When the reaction ions collide with the sample molecules, a chemical reaction occurs, and the sample molecules are ionized.

FIG. 3 is a diagram showing an example of a conventional configuration of a mass spectrometer using an ion source based on CI. The ionization chamber 11, the ion lens 12, the quadrupole filter 13, the detector 14, and the like are arranged in a vacuum housing 10, and the vacuum housing 10 is maintained in a vacuum state by a vacuum pump 15. A sample gas flow path 20 for introducing a sample gas is connected to the ionization chamber 11, and first and second valves 23 and 24 are provided in a reaction gas flow path 21 and a standard sample gas flow path 22, respectively. , Both valves 23,
At the outlet side of 24, the two flow paths 21 and 22 join and are connected to the ionization chamber 11.

In the mass spectrometer, prior to the actual analysis of the sample, the parameters of each part (for example, the voltage applied to the ion lens 12 or the quadrupole filter 13) are determined using a standard sample whose components are known. It makes adjustments and obtains correction information for correcting a shift in the mass number when a mass spectrum is created. At the time of such parameter adjustment, the first
The second valves 23 and 24 are opened, and the reaction gas and the standard sample gas are mixed and introduced into the ionization chamber 11. The reaction gas molecules collide with the electron flow in the ionization chamber 11 to become reaction gas ions, which chemically react with the standard sample molecules and ionize them. The generated ions are ejected from the ionization chamber 11 and an ion lens 12 to which an appropriate voltage is applied.
Are converged and accelerated, and are introduced into the quadrupole filter 13. The quadrupole filter 13 passes only ions having a specific mass number, and the ions are detected by the detector 14. The parameter adjustment of each unit is executed while monitoring the detection signal at this time.

When an actual sample is analyzed, the second valve 24
Is closed to stop the standard sample gas, while the sample gas is introduced into the ionization chamber 11 through the sample gas flow path 20. Therefore, in the ionization chamber 11, the reaction gas ions and the sample molecules cause a chemical reaction, and the ions of the sample molecules fly out of the ionization chamber 11 and are analyzed.

[0006]

However, in the above-described conventional configuration, even when the second valve 24 is closed, the standard sample gas remains in the flow path from the outlet of the second valve 24 to the junction P. The reaction gas containing the standard sample gas remains from the junction P to the ionization chamber 11. Since the residual standard sample gas becomes background noise when the target sample is analyzed, the analysis of the sample cannot be started until the standard sample gas is completely exhausted. In particular, negative ion chemical ionization (NICI = Negative
In high-sensitivity analysis by Ion Chemical Ionization, etc., even a small amount of standard sample gas affects the analysis result, so it is necessary to wait a long time after parameter adjustment work before actually starting the analysis. There was a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to quickly remove an undesired standard sample gas at the time of analysis so that the target sample can be quickly adjusted after parameter adjustment. An object of the present invention is to provide a mass spectrometer provided with an ion source capable of starting analysis.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. The present invention provides a mass spectrometer provided with an ionization chamber for ionizing sample molecules by a chemical reaction with reaction gas ions. A first valve provided with a first valve for supplying a reaction gas;
A flow path; b) a second flow path provided with a second valve for supplying a standard sample gas; and c) a point where the first and second flow paths meet at the outlet side of the first and second valves. D) a discharge connected to a vacuum chamber or a vacuum exhaust means via a third valve from the common flow path or a flow path between the first valve and the second valve; E) when the ionization of the standard sample gas molecules, the third valve is closed and the first and second valves are opened to introduce the reaction gas and the standard sample gas into the ionization chamber, and after the ionization is completed, In order to discharge the standard sample gas remaining in the flow path and the flow path between the first valve and the second valve through the discharge flow path, the first to third valves are closed so that the second valve is opened and the third valve is opened. And control means for controlling the three valves.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS At the time of adjusting the parameters of the mass spectrometer, the control means controls to open the first and second valves and close the third valve. Thereby, the reaction gas supplied to the first flow path and the standard sample gas supplied to the second flow path are mixed and introduced into the ionization chamber through the common flow path. In the ionization chamber, first, the reaction gas is ionized by, for example, collision with an electron flow, and the standard sample molecules are ionized by a chemical reaction with the reaction gas ions.

After the parameter adjustment operation is completed, the control means closes the first and second valves and opens the third valve. As a result, the new inflow of the reaction gas and the standard sample gas is stopped, and the gas remaining in the common channel and the channel between the first valve and the second valve (mixing of the standard sample gas and the reaction gas) is stopped. Gas) is sucked to the vacuum side and is forcibly exhausted through a discharge channel. After the residual gas has been sufficiently exhausted, the third valve is closed and the first valve is opened to introduce a reaction gas into the ionization chamber and introduce a target sample gas to perform ionization.

[0011]

Thus, according to the mass spectrometer of the present invention, the standard sample gas remaining in the flow path and in the ionization chamber, which is undesired when the target sample is analyzed, can be quickly removed after the parameter adjustment. Exhausted. Therefore, the sample gas can be immediately introduced into the ionization chamber after the parameter adjustment is completed, and the analysis can be started, so that the efficiency of the analysis can be improved. Further, since the standard sample gas remaining in the channel and in the ionization chamber is reliably exhausted, high-sensitivity and high-accuracy analysis can be performed without being affected by the standard sample gas.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the mass spectrometer according to the present invention will be described below with reference to FIG. FIG. 1 is a configuration diagram showing the mass spectrometer of the present embodiment, and the configuration of a gas flow path connected to the ionization chamber 11 is different from the conventional one. That is, in the present embodiment, the first valve 23 provided in the reaction gas flow path 21 and the second valve 24 provided in the standard sample gas flow path 22
A bypass flow path 26 provided with a third valve 25 is connected to the flow path between the first and second valves, and the bypass flow path 26 is connected to the vacuum housing 10.

When adjusting the parameters of each part of the mass spectrometer and then analyzing the target sample, the valve control unit 27
Upon receiving an instruction signal from a control unit (not shown) for controlling the operation of the entire mass spectrometer, the first to third valves 2
3, 24 and 25 are controlled to open and close.

When the mass spectrometer is in a stopped state, that is, when neither the parameter adjustment operation nor the analysis operation is performed, the valve control unit 27 controls the first to third valves 23, 2
It controls so that 4, 25 may be closed.

When the control section instructs the start of the parameter adjustment operation, the valve control section 27 controls the first and second valves 23 and 24 to open. Thereby, the reaction gas and the standard sample gas are mixed and introduced into the ionization chamber 11. Normally, the standard sample gas is a very small amount of several percent or less of the reaction gas. The molecules of the reaction gas introduced into the ionization chamber 11 are ionized by the collision of the electron flow, and the generated reaction gas ions chemically react with the standard sample molecules to ionize the molecules. The ions of the standard sample molecules fly out of the ionization chamber 11, are converged and accelerated by the ion lens 12, and are ionized to have a specific mass number by the quadrupole filter (may be another mass analyzer such as a magnetic mass analyzer) 13. Is selected and detected by the detector 14. Since the sample components contained in the standard sample gas are known, the detection result is used to adjust, for example, the voltage applied to the quadrupole filter 13 so that the spectrum of ions having a desired mass number appears. Adjustment is performed such as adjusting the voltage applied to the ion lens 12 so that the height becomes maximum, or creating correction information for correcting a shift in the mass number of the peak appearing in the mass spectrum.

When such parameter adjustment work is completed,
Upon receiving an instruction signal for ending the adjustment operation from the control unit, the valve control unit 27 sends the first and second valves 23 and 24 to each other.
Is controlled to be closed. Thus, the supply of the standard sample gas and the reaction gas to the ionization chamber 11 is stopped.
However, in this state, the standard sample gas remains in the flow path from the second valve 24 to the junction P, and the flow path from the junction P to the ionization chamber 11 and the ionization chamber 1
In 1, a mixed gas of the reaction gas and the standard sample gas remains.

Next, the valve control section 27 controls the third valve 25 to open. Then, since the degree of vacuum in the vacuum housing 10 is higher than the degree of vacuum in the ionization chamber 11, the gas remaining in the flow path flows into the vacuum housing 10 through the bypass flow path 26, and the first valve 23 and the The standard sample gas remaining in the flow path between the two valves 24 and the ionization chamber 11 is almost completely eliminated in a short time. The valve control unit 27 controls the third valve 25 to be opened for a predetermined time, then the valve is closed, and then the first valve 23 is opened. Thereby, the reaction gas is supplied to the ionization chamber 11 through the flow path after the undesired gas is discharged. Then, the sample gas is introduced into the ionization chamber 11 through the sample gas flow path 20, and a desired analysis is performed.

By the way, the control of the opening / closing operation of the valve as described above can be simplified by the following configuration. FIG. 2 is a configuration diagram of this valve control. The valve is
For example, it is opened when a control signal of logic "1" is given,
It closes when a control signal of logic "0" is given. The control signal given to the first valve 23 is given to the third valve 25 via the inversion gate 28. That is, the first mode in which the first valve 23 is opened and the third valve 25 is closed, and the first mode in which the first valve 23 is closed and the third valve 25 is closed.
Has two modes, a second mode to open.

In this configuration, when the standard sample gas is introduced for parameter adjustment and when the sample gas is introduced for sample analysis, the first mode is set. Thereby, the reaction gas is introduced into the ionization chamber 11. Also,
When the forced exhaust is performed after the parameter adjustment, the second mode is set and the second valve 24 is closed. Thereby, the undesired standard sample gas in the flow path and the ionization chamber 11 is discharged into the vacuum housing 10.

The above embodiment is merely an example, and it is apparent that modifications and changes can be made within the spirit of the present invention.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of one embodiment of a mass spectrometer according to the present invention.

FIG. 2 is a configuration diagram of another embodiment of valve control of the mass spectrometer according to the present invention.

FIG. 3 is a configuration diagram of a conventional mass spectrometer.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Vacuum housing 11 ... Ionization chamber 15 ... Vacuum pump 20 ... Sample gas flow path 21 ... Reaction gas flow path 22 ... Standard sample gas flow path 23 ... 1st valve 24 ... 2nd valve 25 ... 3rd valve 26 ... Bypass Channel 27: Valve control unit

Claims (1)

[Claims] 1. A mass spectrometer having an ionization chamber for ionizing sample molecules by a chemical reaction with reaction gas ions, comprising: a) a first valve provided with a first valve for supplying a reaction gas;
A flow path; b) a second flow path provided with a second valve for supplying a standard sample gas; and c) a point where the first and second flow paths meet at the outlet side of the first and second valves. D) a discharge connected to a vacuum chamber or a vacuum exhaust means via a third valve from the common flow path or a flow path between the first valve and the second valve; E) when the ionization of the standard sample gas molecules, the third valve is closed and the first and second valves are opened to introduce the reaction gas and the standard sample gas into the ionization chamber, and after the ionization is completed, In order to discharge the standard sample gas remaining in the flow path and the flow path between the first valve and the second valve through the discharge flow path, the first to third valves are closed so that the second valve is opened and the third valve is opened. Mass spectrometry, comprising: control means for controlling three valves. apparatus.