JPH10223174A - Quadrupole mass spectrometer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve mass resolution by providing four rods serving as the base of quadrupole electrodes, made of an insulating material and multiple coefficient circuits adjusting the power voltages to electrode main bodies to correct the shape error of the radius of the inscribed circle for the rods. SOLUTION: Coefficient circuits 231-236 are adjusted, so that the drive voltage is decreased when quadrupole electrode main bodies 221-226 are assembled at the positions near the center than the normal positions, and the drive voltage is increased when they are assembled apart from the center. Since rods 21 and a supporter supporting four rods 21 are made of the same ceramic material, the distortion in quadrupole electrodes can be reduced when the ambient temperature is changed, and resolution is improved. Electrode shapes can be freely divided by laser machining, the electric field distribution can be finely adjusted, and resolution is improved. Manufacture is efficient because no machining than necessary is applied, and the manufacturing cost can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quadrupole mass spectrometer with improved mass resolution.

[0002]

2. Description of the Related Art FIG. 6 is an explanatory view of the structure of a conventional example generally used in the prior art.
P121, date of issue; September 1, 1996, editor: (company)
Japan Analytical Instruments Manufacturers Association, issuance office;

In the quadrupole mass spectrometer shown in FIG. 6, a sample A introduced into an ion source 1 is ionized by an electron impact method or the like, and then sent to an analysis section 3 having a quadrupole electrode 2, and an electric field is applied. Under the conditions, the traveling and behavior of the ion
The mass spectrometry is performed by the detector 4 using the fact that it is uniquely determined depending on the number of charges (m / z).

[0004] The quadrupole mass spectrometer performs mass spectrometry using only the action of an electric field without using magnetic field conditions. The acceleration voltage of ions is around 10 V, and that of other mass spectrometers using magnetic field conditions. Since it is possible to perform high-sensitivity analysis under a very low voltage as compared with the case of 3 to 10 KV and the structure of the analysis unit 3 is simple, it is small and excellent in operability.
It is used as a highly sensitive detector of gas chromatography (GC) as a device for trace gas analysis or mixture analysis.

[0005] 5 is a power source of the ion source 1, 6 is a quadrupole electrode 2
, A power supply 7 for the detector 4, and a recorder 8 connected to the detector 4.

[0006] As shown in FIG. 6 and FIG.
The metal rods are arranged so as to pass each other and form an electric field having a right-angled hyperbola B. U + Vcosωt and −U−Vcosωt (ω = 2
πf) and the high frequency voltage (Vcosωt) are applied in a superimposed manner.

[0007] When determining the frequency of a frequency f (typically one to several MH _z), the mass number of detected to the detector 4 is determined by the values of U and V, and the value of U / V = constant V under By sweeping linearly, a mass spectrum can be obtained according to the following equation (1). m / z = (1 / 14.438) (V / (r ₀ ² · f ² )) (1) m / z: mass / charge number r ₀ : radius cm V of the inscribed circle of the four rods: High frequency voltage (amplitude: peak to peak value)

[0008] The basic performance is measurable mass range and resolution, the resolution of the apparatus, the processing accuracy of r _0, the stability of the DC voltage and a high frequency voltage, and a vibration number of ions in the analyzer 3 It depends on the square of the dominating frequency f. In addition, the mass range (mass range) is determined by V. In particular, in a quadrupole mass spectrometer, performance is generally represented by the magnitude of the mass range.

As can be seen from equation (1), since the mass / charge number corresponds to the high-frequency voltage V on a one-to-one basis, the spectrum width is constant over the entire mass range from low mass to high mass, and mass calibration is performed. Is one of the outstanding features.

That is, the features are as follows: (1) It is small and compact. (2) Since the accelerating ion source voltage is as low as about 10 V,
It is excellent in operability, and can be expected to be used particularly in application fields such as atmospheric pressure ionization and liquid chromatography (LC) detectors. (3) High-speed scanning and high-speed switching measurement can be performed because mass analysis can be performed only by the action of an electric field. (4) Low price.

[0011]

The above equation (1) is obtained by the following equation: m = V / (K · r ₀ ² · f ² ) K = 14.438 (1) When the equation (1) is totally differentiated, the equation (2) is obtained. Can be (M / Δm) = − (r ₀ / 2Δr ₀ ) − (f / 2Δf) + (V / ΔV) (2) From this equation, the main factor that determines the mass resolution (m / Δm) is the assembly of the rod. It can be seen that there are three points of processing accuracy, frequency stability, and high frequency voltage stability.

As an example, a mass range of 500 and a resolution of 0.5
In order to realize the above, an assembly of 3 μm (when r ₀ = 10 mm)
Processing accuracy, frequency stability of 0.03% and high frequency voltage stability are required. The frequency stability and the stability of the high-frequency voltage have been improved by recent improvements in electronics technology, and the lower limit of resolution is determined by rod processing and processing.
Assembly accuracy. This is particularly noticeable when the diameter of the electrode is reduced to increase the mass number range, or when the resolution is increased by increasing the length of the electrode.

FIG. 8 is a detailed perspective view of the quadruple electrode 2 part. The four metal quadrupole electrodes 2 are held by a support 11 made of ceramics so as to pass through relatively.

The quadruple electrode 2 is generally made mainly of stainless steel, and is made of a ceramic support 1.
When the ambient temperature or the like changes due to the difference between the linear expansion coefficient and 1, the shape distortion occurs. Although there is a quadrupole electrode using molybdenum having a temperature coefficient close to that of ceramics, distortion occurs because the linear expansion coefficients cannot be completely matched. This distortion adversely affects the mass resolution as described above.

The present invention solves these problems. An object of the present invention is to provide a quadrupole mass spectrometer with improved mass resolution.

[0016]

In order to achieve the above object, the present invention provides: (1) an ion source for outputting ions to be analyzed, and a quadrupole electrode for inputting the ions. In a quadrupole mass spectrometer, four rods made of an insulating material and serving as a base of the quadrupole electrode, and a plurality of quadrupoles provided on the surface of the rod and divided in the axial direction of the rod are provided. An electrode body, and the four electrodes respectively connected to the plurality of quadrupole electrode bodies.
A plurality of coefficient circuits adapted to adjust a power supply voltage to the quadrupole electrode body so as to correct a shape error of a radius of an inscribed circle with respect to the plurality of rods. Type mass spectrometer. (2) The quadrupole mass spectrometer according to claim 1, further comprising a quadrupole electrode body whose electrode shape is freely divided by laser processing. (3) a quadrupole electrode body on the input side of ions among two quadrupole electrode bodies provided on the surface of the rod and divided into two parts in the axial direction of the rod, wherein only the high frequency power supply is applied; And a main electrode to which a high-frequency power supply and a DC power supply are applied, which are a quadrupole electrode body on the output side of ions in the two quadrupole electrode bodies. The quadrupole mass spectrometer according to claim 1. (4) First and second quadrupole electrodes provided on the surface of the rod and divided into two equal parts in the axial direction of the rod and having a mass transmission characteristic shifted from the mass axis by a half width or less of the mass transmission characteristic. 4. The quadrupole mass spectrometer according to claim 1, further comprising a main body. (5) The quadrupole mass spectrometer according to claim 1, wherein the material of the rod and a support member for supporting the four rods are made of the same material. Total. (6) The quadrupole mass spectrometer according to claim 5, wherein the material of the rod and the material of the support member are made of ceramics. It is what constituted.

[0017]

In the above configuration, a quadrupole electrode is assembled using four electrodes configured as described above, and a power supply voltage is supplied to each quadrupole electrode body via a coefficient circuit. Hereinafter, a detailed description will be given based on embodiments.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of a main part of an embodiment of the present invention, and shows a detailed explanatory view of one quadrupole electrode 20 constituting a quadrupole electrode. In the figure, the configuration of the same symbol as FIG. 6 represents the same function. Hereinafter, only differences from FIG. 6 will be described.

Reference numeral 21 denotes a rod made of an insulating material and serving as a base of the quadrupole electrode. In this case, ceramics are used. A plurality of quadrupole electrode bodies 221, 22 provided on the surface of the rod 21 and divided in the axial direction of the rod by mechanical processing or the like, and divided and arranged in the axial direction of the rod.
22, 223, 224, 225, 226. In this case, it is divided into six, and for example, stainless steel or gold is used.

Reference numeral 23 denotes a plurality of quadrupole electrode main bodies 221,
22, 223, 224, 225, and 226, respectively, so as to correct the shape error of the radius r ₀ of the inscribed circle with respect to the rod described above.
2, 223, 224, 225, 226, a plurality of coefficient circuits 231, 232,
233, 234, 235, 236.

In the above configuration, as shown in FIG. 2, four electrodes 20 (20a, 20a)
b, 20c, 20d) to assemble the quadrupole electrodes and to form the individual quadrupole electrode bodies 221, 222, 223, 2
24, 225, 226, coefficient circuits 231, 232, 2
A power supply voltage is supplied via 33, 234, 235, 236.

FIG. 6 shows a hyperboloid electric field generated by the quadrupole electrode. This electric field distribution is distorted if there is a processing / assembly error in the quadrupole electrode, and appears as degradation in resolution.

In the present invention, each electrode 2 is divided so as to correct the distortion of the hyperbolic electric field due to the processing / assembly error.
The drive voltages to 21, 222, 223, 224, 225, 226 are applied to coefficient circuits 231, 232, 233, 234, 2
Adjustment was made via 35 and 236.

As a result, the quadrupole electrode is improved so that an accurate electric field distribution can be formed, and a quadrupole mass spectrometer with improved resolution can be obtained.

Specifically, the electrodes 221, 222, 22
When the positions of 3,224, 225, and 226 are assembled closer to the center than the regular positions, the drive voltage is adjusted to be smaller, and when assembled away from the regular positions, the drive voltage is adjusted. May be adjusted by the coefficient circuits 231, 232, 233, 234, 235, and 236 so as to be larger, that is, a feature is that fine adjustment can be performed after assembly.

The material of the rod 21 and the four rods 2
1 is made of the same ceramic material, the distortion of the quadrupole electrode when the ambient temperature or the like changes can be reduced, and a quadrupole mass spectrometer with improved resolution can be obtained. .

Next, the quadrupole electrode bodies 221, 222, 223, 2 whose electrode shapes are freely divided by laser processing
With the configuration of 24, 225, 226, even after the quadrupole electrode is assembled, the quadrupole electrode main bodies 221, 222, 223, 224, 225, 2 are formed by laser processing.
26 divisions are possible. Further, fine electric field distribution can be adjusted, and a quadrupole mass spectrometer with improved resolution can be obtained.

Further, when the assembled quadrupole electrode has a desired assembling accuracy, it is not necessary to perform the processing, and it is not necessary to perform the processing more than necessary. , A quadrupole mass spectrometer capable of reducing the amount of water is obtained.

FIG. 3 is an explanatory diagram of a main part configuration of another embodiment of the present invention. In the present embodiment, 31 is a quadrupole electrode main body on the input side of ions among two quadrupole electrode main bodies provided on the surface of the rod 21 and divided into two in the axial direction of the rod 21. , A pre-electrode to which only the high-frequency power supply 32 is applied. Reference numeral 33 denotes a quadrupole electrode main body on the output side of ions of the two quadrupole electrode main bodies, which is a main electrode to which a quadrupole power supply 34 composed of a high-frequency power supply and a DC power supply is applied.

In order to prevent disturbance of the electric field at the end of the high-precision mass spectrometer, a pre-electrode in which the quadrupole electrode is short and only the high-frequency electric field is applied is separately installed in front of the main quadrupole electrode. doing. Since the two types of quadrupole electrodes are separately manufactured, the cost is high, and the positions of the two quadrupole electrodes must be accurately matched.

On the other hand, in this embodiment, the quadrupole electrode body is divided into a pre-electrode 31 and a main electrode 33, the pre-electrode 31 is driven by a high frequency power supply 32, and the main electrode 33 is a normal quadrupole electrode. By driving with the power supply 34, the pre-electrode 31 and the main electrode 33 can be integrally formed, and the position adjustment between the pre-electrode 31 and the main electrode 33 becomes unnecessary.

As a result, a quadrupole mass spectrometer can be obtained which can improve the accuracy and reduce the position adjustment cost.

FIG. 4 is an explanatory diagram of a main part configuration of another embodiment of the present invention. In this embodiment, 41 and 42 are rods 2
1 and is divided into two equal parts in the axial direction of the rod 21, and as shown in FIG.
Are the first and second quadrupole electrode bodies which are shifted with respect to the mass axis C by not more than the half width of the mass transmission characteristics 411 and 421.

As a result, a quadrupole mass spectrometer can be obtained which can obtain a higher resolution than the mass resolution which can be realized by itself.

[0035]

As described above in detail, according to the first aspect of the present invention, the drive voltage to each of the divided electrodes is adjusted so as to correct the distortion of the hyperbolic electric field due to the processing / assembly error.
The adjustment is made via a coefficient circuit.

As a result, the quadrupole electrode is improved so that an accurate electric field distribution can be formed, and a quadrupole mass spectrometer with improved resolution can be obtained. Further, a fine adjustment can be performed by a coefficient circuit after assembly, and a quadrupole mass spectrometer with improved resolution can be obtained.

That is, the mass resolution of the quadrupole mass spectrometer is often limited by the electrode processing and assembly accuracy. On the other hand, in the present invention, the disturbance of the electric field distribution due to the shape error is corrected by dividing the electrode into a plurality of parts and adjusting the voltage applied to each electrode so as to cancel the disturbance of the electric field distribution. As a result, a quadrupole mass spectrometer with improved resolution is obtained.

According to the second aspect of the present invention, since the quadrupole electrode body whose electrode shape is freely divided by laser processing is constituted, even after the quadrupole electrode is assembled, laser processing is performed. Because it is possible to divide the quadrupole electrode body. Further, fine electric field distribution can be adjusted, and a quadrupole mass spectrometer with improved resolution can be obtained.

Further, when the assembled quadrupole electrode has the desired assembly accuracy, it is not necessary to perform the processing, and it is not necessary to perform the processing more than necessary. , A quadrupole mass spectrometer capable of reducing the amount of water is obtained.

According to the third aspect of the present invention, the quadrupole electrode body is divided into a pre-electrode and a main electrode, the pre-electrode is driven by a high-frequency power source, and the main electrode is driven by a normal quadrupole power source. Thereby, the pre-electrode and the main electrode can be integrally formed, and the position adjustment between the pre-electrode and the main electrode becomes unnecessary. As a result, a quadrupole mass spectrometer that can improve the accuracy and reduce the position adjustment cost can be obtained.

According to the fourth aspect of the present invention, the first and second quadrupole electrode bodies are divided into two equal parts in the axial direction of the rod, and their mass transmission characteristics are relative to the mass axis. Are shifted from each other by less than the half width.

As a result, a quadrupole mass spectrometer capable of obtaining high resolution as compared with the mass resolution that can be realized by itself can be obtained.

According to the fifth aspect of the present invention, since the material of the rod and the supporting member for supporting the four rods are made of the same material, the distortion of the quadruple electrode when the ambient temperature or the like changes is reduced. A quadrupole mass spectrometer that can be made smaller and has improved resolution can be obtained.

According to claim 6 of the present invention, in the prior art, the rod is made of metal, and the support of the rod is made of ceramics to maintain insulation against high voltage. Therefore, although distortion occurs due to the difference in linear expansion coefficient due to the material, in the present invention, since the rod is made of the same ceramic as the support, the rod has the same linear expansion coefficient, and the quadruple electrode when the ambient temperature or the like changes. Distortion can be reduced and a quadrupole mass spectrometer with improved resolution can be obtained.

Therefore, according to the present invention, a quadrupole mass spectrometer with improved mass resolution can be realized.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a main part configuration of an embodiment of the present invention.

FIG. 2 is an overall explanatory diagram of FIG.

FIG. 3 is an explanatory diagram of a main part configuration of another embodiment of the present invention.

FIG. 4 is an explanatory diagram of a main part configuration of another embodiment of the present invention.

FIG. 5 is an operation explanatory diagram of FIG. 4;

FIG. 6 is an explanatory diagram of a configuration of a conventional example generally used in the related art.

FIG. 7 is a detailed explanatory view of a main part of FIG. 6;

FIG. 8 is a perspective view of a main part of FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ion source 2 Quadrupole electrode 3 Analysis part 4 Detector 5 Power supply 6 Power supply 7 Power supply 8 Recorder 11 Support 20 Electrode 20a Electrode 20b Electrode 20c Electrode 20d Electrode 21 Rod 22 Quadrupole electrode main body 221 Quadrupole electrode main body 222 Quadrupole electrode body 223 Quadrupole electrode body 224 Quadrupole electrode body 225 Quadrupole electrode body 226 Quadrupole electrode body 23 Coefficient circuit 231 Coefficient circuit 232 Coefficient circuit 233 Coefficient circuit 234 Coefficient circuit 235 Coefficient circuit 236 Coefficient Circuit 31 Pre-electrode 32 High-frequency power supply 33 Main electrode 34 Quad electrode power supply 41 First quadrupole electrode main body 411 Mass transmission characteristic 42 Second quadrupole electrode main body 421 Mass transmission characteristic A Sample B Hyperbolic C Mass axis

Claims (6)

[Claims] 1. A quadrupole mass spectrometer comprising: an ion source from which ions to be analyzed are output; and a quadrupole electrode to which the ions are input, wherein the quadrupole mass spectrometer is made of an insulating material. Four rods serving as a base; a plurality of quadrupole electrode bodies provided on the surface of the rod and divided in the axial direction of the rod; and the four quadrupole electrode bodies respectively connected to the plurality of quadrupole electrode bodies. And a plurality of coefficient circuits adapted to adjust a power supply voltage to the quadrupole electrode body so as to correct a shape error of a radius of an inscribed circle with respect to the rod. Mass spectrometer. 2. The quadrupole mass spectrometer according to claim 1, further comprising a quadrupole electrode body whose electrode shape is freely divided by laser processing. 3. A quadrupole electrode main body on the input side of ions among two quadrupole electrode main bodies provided on the surface of the rod and divided into two in the axial direction of the rod, wherein only the high frequency power supply is provided. A pre-electrode to be applied; and a main electrode to which a high-frequency power supply and a DC power supply are applied, the quadrupole electrode body being an ion output side of the two quadrupole electrode bodies. The quadrupole mass spectrometer according to claim 1 or 2, wherein 4. The first and second quadruples which are provided on the surface of the rod and are equally divided in the axial direction of the rod and whose mass transmission characteristics are shifted from each other by a half width of the mass transmission characteristic with respect to the mass axis. 4. The quadrupole mass spectrometer according to claim 1, further comprising a pole electrode body. 5. The quadrupole type according to claim 1, wherein said rod material and a support member for supporting said four rods are made of the same material. Mass spectrometer. 6. A material according to claim 5, wherein said rod material and said support member are made of ceramics.
The quadrupole mass spectrometer as described.