WO1994014184A1 - Quadrupole mass filter - Google Patents

Quadrupole mass filter Download PDF

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Publication number
WO1994014184A1
WO1994014184A1 PCT/EP1993/003532 EP9303532W WO9414184A1 WO 1994014184 A1 WO1994014184 A1 WO 1994014184A1 EP 9303532 W EP9303532 W EP 9303532W WO 9414184 A1 WO9414184 A1 WO 9414184A1
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WO
WIPO (PCT)
Prior art keywords
frequency
alternating voltage
voltage
amplitude
mass filter
Prior art date
Application number
PCT/EP1993/003532
Other languages
German (de)
French (fr)
Inventor
Norbert Rolff
Original Assignee
Leybold Aktiengesellschaft
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Leybold Aktiengesellschaft filed Critical Leybold Aktiengesellschaft
Publication of WO1994014184A1 publication Critical patent/WO1994014184A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/26—Mass spectrometers or separator tubes
    • H01J49/34—Dynamic spectrometers
    • H01J49/42—Stability-of-path spectrometers, e.g. monopole, quadrupole, multipole, farvitrons
    • H01J49/4205—Device types
    • H01J49/421—Mass filters, i.e. deviating unwanted ions without trapping
    • H01J49/4215—Quadrupole mass filters

Definitions

  • Mass spectrometers are used for the analysis of substances for constituents of various masses and for precise mass determination.
  • the substance to be analyzed is fed to an ion source in a mass spectrometer and ionized there.
  • the ions are accelerated in an electric field, so that a focused ion beam is created.
  • the ion beam is then broken down into its various mass fractions in a mass filter.
  • the electrical charge of the individual components is e.g. given to a receiver, the current measured there being proportional to the intensity of the respective mass.
  • the known quadrupole mass filters for mass spectrometers have four rod electrodes arranged concentrically parallel to one another. There is a DC voltage on each pair of opposing electrodes, which of a high-frequency AC voltage is superimposed.
  • mass filters are also known, the rod electrodes of which are only connected to a high-frequency AC voltage.
  • the ion beam in the interior of the quadrupole mass filter is excited by the high-frequency field to vibrations that are mass-dependent. Only for ions of a certain mass does the oscillation amplitude remain so small that they pass through the rod system and reach the receiver. The other ions hit the stick electrodes and are eliminated. Depending on the amplitude and frequency of the AC voltage, ions of a certain mass can be focused (Rö pp, 9th edition, p. 2648, quadrupole mass spectrometer).
  • Quadrupole mass filters which have a freely oscillating oscillator, the frequency of the high-frequency alternating voltage being predetermined by the resonance frequency of an HF oscillating circuit.
  • Such mass filters are simple in construction and have a relatively low power requirement.
  • the frequency of the AC voltage is not stable. Frequency shifts of the AC voltage, e.g. due to temperature fluctuations lead to measurement inaccuracies.
  • More exact measurement results can be achieved with mass filters which have a quartz-controlled oscillator, the resonance frequency of the HF oscillating circuit being readjusted with a transducer coil.
  • Such an arrangement guarantees a stable frequency.
  • the manufacture of the circuit is relatively expensive and the power requirement is relatively high.
  • the invention has for its object to provide a mass filter with a high measurement accuracy and a relatively simple structure. This object is achieved according to the invention with the features specified in claim 1.
  • a compensation device which has a frequency measuring device which measures the actual frequency of the high-frequency AC voltage. By comparing the actual frequency of the AC voltage and the target frequency, frequency deviations of the AC voltage from the target frequency can be detected.
  • the compensation device changes the amplitude value of the alternating voltage, which is specified for the focusing of the ions at the desired frequency of the alternating voltage, as a function of the frequency deviation found.
  • the compensation device compensates for a change in frequency of the alternating voltage applied to the electrodes by changing the amplitude value of the alternating voltage, so that frequency shifts in the alternating voltage do not lead to changes in the mass spectrum.
  • the AC voltage source can have a free-running oscillator with low power requirements, which is simple in construction and inexpensive to manufacture. Complex circuitry measures for stabilizing the frequency of the alternating voltage can be omitted in the mass filter according to the invention.
  • the correction factor for the amplitude value of the AC voltage corresponding to the target frequency is advantageously calculated in a computing unit from the quotient of the square of the measured actual frequency and the square of the predetermined target frequency of the AC voltage.
  • the control device gives an amplitude value for the AC voltage, which corresponds to the product of the amplitude value, which corresponds to the target frequency, and the determined correction factor.
  • the level of the direct voltage is approximately proportional to the level of the alternating voltage. If the amplitude value of the AC voltage changes through the compensation device, the DC voltage can be readjusted accordingly.
  • FIG. 2 shows a simplified block diagram of the mass filter supply.
  • the quadrupole mass filter has four ⁇ -shaped electrodes 1, 1 'and 3, 3' arranged concentrically parallel to one another in a high vacuum.
  • a direct voltage is applied to each pair of opposite stick electrodes 1, 1 'and 3, 3', which is superimposed by a high-frequency alternating voltage.
  • the ion beam 5 in the interior of the rod system is excited by the high-frequency field to vibrations of different amplitudes, which are dependent on the antenna. Only for ions of a certain mass does the amplitude of the vibrations remain so small that they pass through the rod system and are catcher 7 arrive. The other ions hit the rod-shaped electrodes and are eliminated.
  • the maximum mass of the ions passing through the rod system is proportional to the alternating voltage applied to each pair of rod electrodes 1, 1 'and 3,3' and inversely proportional to the square of the frequency of the high-frequency alternating voltage.
  • the filter characteristic can thus be changed by changing the amplitude values of the AC voltage and the frequency of the AC voltage.
  • the resolution of the mass filter depends on the amplitude value of the DC voltage.
  • each pair of opposite stick electrodes 1, 1 'and 3, 3' is electrically connected to one another. Between the one pair of electrodes 1, 1 'and the other pair of electrodes 3, 3' there is a series circuit consisting of a first coil 9, a capacitor 11 and a second coil 13. Furthermore, two capacitors 15, 17 are provided, each between an electrical unit ⁇ the pair 1.1 'and 3.3' and mass.
  • the mass filter supply also has a DC voltage source 19 which supplies a DC voltage of variable amplitude, the amplitude value of the DC voltage depending on the level of a control voltage present at the control input 21 of the DC voltage source 19.
  • the output 23 of the DC voltage source 19 is connected to the capacitor 11 arranged between the coils 9, 13, so that the two electrode pairs 1, 1 'and 3, 3' are at different potentials.
  • the HF generator 27 can be a freely oscillating oscillator, the actual frequency of the AC voltage applied to the rod electrodes being determined by the resonance frequency of the coil 9, 13, 25, the capacitors 11, 15, 17 and the capacitance of the rod. electrode system consisting of a resonant circuit.
  • a control device 31 which supplies the control voltages for the HF generator 27 and the direct voltage source 19.
  • a compensation device is provided to compensate for frequency shifts in the alternating voltage, which can be attributed, for example, to the temperature coefficients of the inductances and the capacitances of the HF oscillating circuit.
  • the modules belonging to the compensation device 33 are outlined in FIG. 2 with a dashed line.
  • the compensation device has a digital frequency counter 35, which measures the actual frequency f ⁇ of the alternating voltage generated by the HF generator 27.
  • the compensation circuit changes the amplitude value of the AC voltage predetermined for the focusing of the ions as a function of the frequency deviation from the target frequency f. the alternating voltage. It has a computing unit 37 which calculates a correction factor for the amplitude value of the alternating voltage, which corresponds to the target frequency.
  • the correction factor is calculated from the quotient of the square of the measured actual frequency f 1 and the square of the predetermined target frequency f. the AC voltage.
  • the corrected amplitude value of the alternating voltage is the product of the predetermined amplitude value and the correction factor.
  • the computing unit 37 is coupled to the control device 31.
  • the control device 31 sets an alternating voltage with an amplitude that corresponds to the it frequency of the alternating voltage. It also corrects the amplitude value of the DC voltage, which is proportional to the amplitude value of the AC voltage.
  • the computing unit and the frequency counter can be part of a single microprocessor and can be constructed inexpensively.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Electron Tubes For Measurement (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)

Abstract

A mass filter has four concentric and parallel rod electrodes (1, 1', 3, 3'), a direct voltage source (19) and a high-frequency alternating voltage source for each pair of opposite rod electrodes. The rod electrodes generate a quadripolar field for focussing ions having a determined mass depending on the frequency and the amplitude of the alternating voltage. In addition, a compensating arrangement (33) has a frequency measurement arrangement which measures the real frequency of the high-frequency alternating voltage in order to detect changes in frequency of the alternating voltage. The compensating arrangement (33) modifies the ion focussing predetermined amplitude value of the alternating voltage depending on the change in frequency, so that frequency shifts of the alternating voltage do not lead to changes in the mass spectrum.

Description

Quadrupol-Massenfilter Quadrupole mass filter
Zur Analyse von Substanzen auf Bestandteile verschie¬ dener Masse und zur genauen Massenbestimmung finden Massenspektro eter Verwendung. In einem Massenspektro- eter wird die zu analysierende Substanz einer Ionen¬ quelle zugeführt und dort ionisiert. Die Ionen werden in einem elektrischen Feld beschleunigt, so daß ein gebündelter Ionenstrahl entsteht. In einem Massenfilter wird der Ionenstrahl dann in seine verschiedenen Masse- anteile zerlegt. Die elektrische Ladung der einzelnen Bestandteile wird z.B. an einen Auffänger abgegeben, wobei der dort gemessene Strom der Intensität der je¬ weiligen Masse proportional ist.Mass spectrometers are used for the analysis of substances for constituents of various masses and for precise mass determination. The substance to be analyzed is fed to an ion source in a mass spectrometer and ionized there. The ions are accelerated in an electric field, so that a focused ion beam is created. The ion beam is then broken down into its various mass fractions in a mass filter. The electrical charge of the individual components is e.g. given to a receiver, the current measured there being proportional to the intensity of the respective mass.
Die bekannten Quadrupol-Massenfilter für Massenspektro¬ meter weisen vier konzentrisch parallel zueinander an¬ geordnete Stabelektroden auf. An jedem Paar gegenüber¬ liegender Elektroden liegt eine Gleichspannung, die von einer hochfrequenten Wechselspannung überlagert ist. Es sind aber auch Massenfilter bekannt, deren Stabelektro¬ den nur an einer hochfrequenten Wechεelspannung liegen.The known quadrupole mass filters for mass spectrometers have four rod electrodes arranged concentrically parallel to one another. There is a DC voltage on each pair of opposing electrodes, which of a high-frequency AC voltage is superimposed. However, mass filters are also known, the rod electrodes of which are only connected to a high-frequency AC voltage.
Der Ionenstrahl im Inneren des Quadrupol-Massenfilters wird durch das Hochfrequenzfeld zu Schwingungen ange¬ regt, die massenabhängig sind. Nur für Ionen einer be¬ stimmten Masse bleibt die Schwingungsamplitude so klein, daß sie das Stabsystem passieren und in den Auf¬ fänger gelangen. Die anderen Ionen treffen auf die Stabelektroden und werden eliminiert. In Abhängigkeit von der Amplitude und der Frequenz der Wechselspannung können Ionen einer bestimmten Masse fokussiert werden (Rö pp, 9. Auflage, S. 2648, Quadrupol-Massenspektro- meter) .The ion beam in the interior of the quadrupole mass filter is excited by the high-frequency field to vibrations that are mass-dependent. Only for ions of a certain mass does the oscillation amplitude remain so small that they pass through the rod system and reach the receiver. The other ions hit the stick electrodes and are eliminated. Depending on the amplitude and frequency of the AC voltage, ions of a certain mass can be focused (Rö pp, 9th edition, p. 2648, quadrupole mass spectrometer).
Es sind Quadrupol-Massenfilter bekannt, die einen frei¬ schwingenden Oszillator aufweisen, wobei die Frequenz der hochfrequenten Wechselspannung durch die Resonanz¬ frequenz eines HF-Schwingkreises vorgegeben ist. Derar¬ tige Massenfilter sind zwar einfach im Aufbau und haben einen relativ geringen Leistungsbedarf. Die Frequenz der Wechselεpannung ist jedoch nicht stabil. Frequenz¬ verschiebungen der Wechselspannung, z.B. aufgrund von Temperaturschwankungen, führen zu Meßungenauigkeiten. Exaktere Meßergebnisse lassen sich mit Massenfiltern erzielen, die einen quartzgesteuerten Oszillator auf¬ weisen, wobei die Resonanzfrequenz des HF-Schwingkrei¬ ses mit einer Transduktorspule nachgeregelt wird. Eine derartige Anordnung garantiert zwar eine stabile Fre¬ quenz. Die Herstellung der Schaltung ist aber relativ teuer und der Leistungsbedarf ist relativ hoch.Quadrupole mass filters are known which have a freely oscillating oscillator, the frequency of the high-frequency alternating voltage being predetermined by the resonance frequency of an HF oscillating circuit. Such mass filters are simple in construction and have a relatively low power requirement. However, the frequency of the AC voltage is not stable. Frequency shifts of the AC voltage, e.g. due to temperature fluctuations lead to measurement inaccuracies. More exact measurement results can be achieved with mass filters which have a quartz-controlled oscillator, the resonance frequency of the HF oscillating circuit being readjusted with a transducer coil. Such an arrangement guarantees a stable frequency. However, the manufacture of the circuit is relatively expensive and the power requirement is relatively high.
Der Erfindung liegt die Aufgabe zugrunde, einen Massen¬ filter mit einer großen Meßgenauigkeit und einem rela¬ tiv einfachen Aufbau zu schaffen. Die Lösung dieser Aufgabe erfolgt erfindungsgemäß mit den im Patentanspruch 1 angegebenen Merkmalen.The invention has for its object to provide a mass filter with a high measurement accuracy and a relatively simple structure. This object is achieved according to the invention with the features specified in claim 1.
Bei dem erfindungsgemäßen Massenfilter ist eine Kompen¬ sationseinrichtung vorgesehen, die eine die Ist-Fre¬ quenz der hochfrequenten Wechεelspannung messende Fre¬ quenzmeßeinrichtung aufweist. Durch Vergleich der Ist- Frequenz der Wechselspannung und der Soll-Frequenz kön¬ nen Frequenzabweichungen der Wechselspannung von der Soll-Frequenz erfaßt werden. Die Kompensationseinrich¬ tung verändert den Amplitudenwert der Wechselspannung, der für die Fokussierung der Ionen bei der Soll-Fre¬ quenz der Wechselspannung vorgegeben ist, in Abhängig¬ keit von der festgestellten Frequenzabweichung. Die Kompensationseinrichtung gleicht eine Frequenzänderung der an den Elektroden anliegenden Wechselspannung durch eine Änderung des Amplitudenwerts der Wechselspannung aus, so daß Frequenzverschiebungen der Wechselspannung nicht zu Änderungen im Massenspektrum führen.In the mass filter according to the invention, a compensation device is provided which has a frequency measuring device which measures the actual frequency of the high-frequency AC voltage. By comparing the actual frequency of the AC voltage and the target frequency, frequency deviations of the AC voltage from the target frequency can be detected. The compensation device changes the amplitude value of the alternating voltage, which is specified for the focusing of the ions at the desired frequency of the alternating voltage, as a function of the frequency deviation found. The compensation device compensates for a change in frequency of the alternating voltage applied to the electrodes by changing the amplitude value of the alternating voltage, so that frequency shifts in the alternating voltage do not lead to changes in the mass spectrum.
Die Wechselspannungsquelle kann einen freischwingenden Oszillator mit geringem Leistungsbedarf aufweisen, der einfach im Aufbau und preisgünstig herzustellen ist. Aufwendige schaltungstechnische Maßnahmen zur Stabili¬ sierung der Frequenz der Wechselspannunq können bei dem erfindungsgemäßen Massenfilter entfallen.The AC voltage source can have a free-running oscillator with low power requirements, which is simple in construction and inexpensive to manufacture. Complex circuitry measures for stabilizing the frequency of the alternating voltage can be omitted in the mass filter according to the invention.
Der Korrekturfaktor für den der Soll-Frequenz entspre¬ chenden Amplitudenwert der Wechselspannung wird vor¬ teilhaf erweise in einer Recheneinheit aus dem Quotien¬ ten des Quadrats der gemessenen Ist-Frequenz und des Quadrats der vorgegebenen Soll-Frequenz der Wechsel¬ spannung berechnet. Für den Fall einer Frequenzände¬ rung, gibt die Steuereinrichtung einen Amplitudenwert für die Wechselspannung vor, der dem Produkt aus dem Amplitudenwert, der der Soll-Frequenz entspricht, und dem ermittelten Korrekturfaktor entspricht.The correction factor for the amplitude value of the AC voltage corresponding to the target frequency is advantageously calculated in a computing unit from the quotient of the square of the measured actual frequency and the square of the predetermined target frequency of the AC voltage. In the event of a frequency change, the control device gives an amplitude value for the AC voltage, which corresponds to the product of the amplitude value, which corresponds to the target frequency, and the determined correction factor.
Bei Massenfiltern, an deren Elektroden eine Gleichspan¬ nung anliegt, die von der hochfrequenten Wechselspan¬ nung überlagert ist, ist die Höhe der Gleichspannung etwa proportional zur Höhe der Wechεelspannung. Bei einer Veränderung des Amplitudenwerts der Wechεel-span- nung durch die Kompensationseinrichtung kann die Gleichspannung entsprechend nachgeregelt werden.In the case of mass filters, at whose electrodes a direct voltage is applied, which is superimposed by the high-frequency alternating voltage, the level of the direct voltage is approximately proportional to the level of the alternating voltage. If the amplitude value of the AC voltage changes through the compensation device, the DC voltage can be readjusted accordingly.
Im folgenden wird unter Bezugnahme auf die Zeichnungen ein Ausführungsbeispiel der Erfindung näher erläutert.In the following an embodiment of the invention will be explained with reference to the drawings.
Es zeigen:Show it:
Fig. 1 die vier Elektroden des Maεsenfilters in per¬ spektivischer Darstellung und1 shows the four electrodes of the mass filter in a perspective view and
Fig. 2 ein vereinfachtes Blockschaltbild der Massen¬ filter-Versorgung.2 shows a simplified block diagram of the mass filter supply.
Der Quadrupol-Masεenfilter weist vier konzentrisch par¬ allel zueinander im Hochvakuum angeordete εtabför ige Elektroden 1,1' und 3,3' auf. An jedem Paar gegenüber¬ liegender Stabelektroden 1,1' und 3,3' ist eine Gleich¬ spannung gelegt, die von einer hochfrequenten Wechsel¬ spannung überlagert ist. Der Ionenstrahl 5 im Inneren des Stabεyεtems wird durch das Hochfrequenzfeld zu Schwingungen unterschiedlicher Amplitude angeregt, die aεsenabhängig sind. Nur für Ionen einer beεtimmten Maεεe bleibt die Amplitude der Schwingungen εo klein, daß sie daε Stabsystem passieren und auf einen Auf- fänger 7 gelangen. Die anderen Ionen treffen auf die stabförmigen Elektroden und werden eliminiert.The quadrupole mass filter has four ε-shaped electrodes 1, 1 'and 3, 3' arranged concentrically parallel to one another in a high vacuum. A direct voltage is applied to each pair of opposite stick electrodes 1, 1 'and 3, 3', which is superimposed by a high-frequency alternating voltage. The ion beam 5 in the interior of the rod system is excited by the high-frequency field to vibrations of different amplitudes, which are dependent on the antenna. Only for ions of a certain mass does the amplitude of the vibrations remain so small that they pass through the rod system and are catcher 7 arrive. The other ions hit the rod-shaped electrodes and are eliminated.
Die maximale Masse der durch das Stabsyεtem hindurch¬ tretenden Ionen iεt proportional zu der an jedem Paar gegenüberliegender Stabelektroden 1,1' und 3,3' anlie¬ genden Wechεelεpannung und umgekehrt proportional zu dem Quadrat der Frequenz der hochfrequenten Wechsel¬ spannung. Durch Veränderung der Amplitudenwerte der Wechεelεpannung und der Frequenz der Wechεelεpannung kann die Filtercharakteristik also verändert werden. Das Auflösungsvermögen des Massenfilters ist abhängig von dem Amplitudenwert der Gleichspannung.The maximum mass of the ions passing through the rod system is proportional to the alternating voltage applied to each pair of rod electrodes 1, 1 'and 3,3' and inversely proportional to the square of the frequency of the high-frequency alternating voltage. The filter characteristic can thus be changed by changing the amplitude values of the AC voltage and the frequency of the AC voltage. The resolution of the mass filter depends on the amplitude value of the DC voltage.
Fig. 2 zeigt ein vereinfachtes Blockεchaltbild der Maεεenfilter-Verεorgung. Jedeε Paar gegenüberliegender Stabelektroden 1,1' und 3,3' ist elektrisch miteinander verbunden. Zwischen dem einen Elektrodenpaar 1,1' und dem anderen Elektrodenpaar 3,3' liegt eine Serienschal¬ tung aus einer ersten Spule 9, einem Kondensator 11 und einer zweiten Spule 13. Ferner sind zwei Kondensatoren 15,17 vorgesehen, die jeweils zwischen einem Elektro¬ denpaar 1,1' und 3,3' und Masse liegen.2 shows a simplified block diagram of the mass filter supply. Each pair of opposite stick electrodes 1, 1 'and 3, 3' is electrically connected to one another. Between the one pair of electrodes 1, 1 'and the other pair of electrodes 3, 3' there is a series circuit consisting of a first coil 9, a capacitor 11 and a second coil 13. Furthermore, two capacitors 15, 17 are provided, each between an electrical unit ¬ the pair 1.1 'and 3.3' and mass.
Die Masεenfilter-Versorgung weist ferner eine Gleich¬ spannungsquelle 19 auf, die eine Gleichspannung variab¬ ler Amplitude liefert, wobei der Amplitudenwert der Gleichspannung abhängig von der Höhe einer an dem Steu¬ ereingang 21 der Gleichεpannungsquelle 19 anliegenden Steuerspannung ist. Der Auεgang 23 der Gleichεpannungs¬ quelle 19 iεt mit dem zwischen den Spulen 9,13 angeord¬ neten Kondensator 11 verbunden, so daß die beiden Elek¬ trodenpaare 1,1' und 3,3' auf unterschiedlichem Poten¬ tial liegen. Eine elektrisch zwischen den beiden äuße¬ ren Spulen 9,13 geschaltete mittlere Spule 25 überträgt die hochfrequente Wechselspannung eines HF-Generators 27, dessen Amplitude variabel und abhängig von der an dem Steuereingang 29 des Generators 27 anliegenden Steuerspannung ist. Der HF-Generator 27 kann ein frei¬ schwingender Oszillator sein, wobei die Ist-Frequenz der an den Stabelektroden anliegenden Wechεelspannung durch die Resonanzfrequenz des aus den Spulen 9,13,25, den Kondensatoren 11,15,17 und der Kapazität des Stab- elektrodenεystems beεtehenden Schwingkreises vorgegeben ist.The mass filter supply also has a DC voltage source 19 which supplies a DC voltage of variable amplitude, the amplitude value of the DC voltage depending on the level of a control voltage present at the control input 21 of the DC voltage source 19. The output 23 of the DC voltage source 19 is connected to the capacitor 11 arranged between the coils 9, 13, so that the two electrode pairs 1, 1 'and 3, 3' are at different potentials. A middle coil 25, which is electrically connected between the two outer coils 9, 13, transmits the high-frequency alternating voltage of an HF generator 27, the amplitude of which is variable and dependent on the control voltage present at the control input 29 of the generator 27. The HF generator 27 can be a freely oscillating oscillator, the actual frequency of the AC voltage applied to the rod electrodes being determined by the resonance frequency of the coil 9, 13, 25, the capacitors 11, 15, 17 and the capacitance of the rod. electrode system consisting of a resonant circuit.
Zur Einεtellung der Amplitudenwerte der Gleichεpannung und der Wechεelεpannung iεt eine Steuereinrichtung 31 vorgesehen, die die Steuerspannungen für den HF-Gene¬ rator 27 und die Gleichspannungsquelle 19 liefert. Der ursprüngliche Amplitudenwert der•Wechselεpannung iεt εo eingestellt, daß bei einer Wechselεpannung mit der Soll-Frequenz die Ionen einer bestimmten Masse fokus¬ siert werden.To set the amplitude values of the direct voltage and the alternating voltage, a control device 31 is provided, which supplies the control voltages for the HF generator 27 and the direct voltage source 19. The initial value of the amplitude • Wechselεpannung iεt εo adjusted that with a Wechselεpannung with the target frequency, the ions of a particular mass are Siert fokus¬.
Zur Kompensation von Frequenzverschiebungen der Wechselspannung, die z.B. auf die Temperaturkoeffizien¬ ten der Induktivitäten und der Kapazitäten des HF-Schwingkreiεeε zurückzuführen εind, iεt eine Kompen¬ sationseinrichtung vorgesehen. Die zu der Kompenεa- tionεeinrichtung 33 gehörenden Baugruppen sind in Fig. 2 mit einer geεtrichelten Linie umrandet. Die Kompenεa- tionseinrichtung weist als Frequenzmeßeinrichtung einen digitalen Frequenzzähler 35 auf, der die Ist-Frequenz f~ der von dem HF-Generator 27 erzeugten Wechselεpan¬ nung mißt. Die Kompensationsschaltung verändert den für die Fokussierung der Ionen vorgegebenen Amplitudenwert der Wechselspannung in Abhängigkeit von der Frequenzab¬ weichung von der Soll-Frequenz f. der Wechεelεpan¬ nung. Sie weist eine Recheneinheit 37 auf, die einen •Korrekturfaktor für den Amplitudenwert der Wechse.lspan- nung, der der Soll-Frequenz entεpricht, berechnet. Der Korrekturfaktor berechnet sich aus dem Quotienten des Quadrats der gemesεenen Iεt-Frequenz f„ und deε Quadratε der vorgegebenen Soll-Frequenz f. der Wechsel¬ spannung. Der korrigierte Amplitudenwert der Wechsel¬ εpannung iεt daε Produkt aus dem vorgegebenen Ampli¬ tudenwert und dem Korrekturfaktor. Die Recheneinheit 37 ist an die Steuereinrichtung 31 gekoppelt. Die Steuer¬ einrichtung 31 stellt eine Wechεelεpannung mit einer Amplitude ein, die der Iεt-Frequenz der Wechselspannung entspricht. Sie korrigiert ferner den Amplitudenwert der Gleichspannung, der dem Amplitudenwert der Wechsel¬ spannung proportional ist.A compensation device is provided to compensate for frequency shifts in the alternating voltage, which can be attributed, for example, to the temperature coefficients of the inductances and the capacitances of the HF oscillating circuit. The modules belonging to the compensation device 33 are outlined in FIG. 2 with a dashed line. As a frequency measuring device, the compensation device has a digital frequency counter 35, which measures the actual frequency f ~ of the alternating voltage generated by the HF generator 27. The compensation circuit changes the amplitude value of the AC voltage predetermined for the focusing of the ions as a function of the frequency deviation from the target frequency f. the alternating voltage. It has a computing unit 37 which calculates a correction factor for the amplitude value of the alternating voltage, which corresponds to the target frequency. The correction factor is calculated from the quotient of the square of the measured actual frequency f 1 and the square of the predetermined target frequency f. the AC voltage. The corrected amplitude value of the alternating voltage is the product of the predetermined amplitude value and the correction factor. The computing unit 37 is coupled to the control device 31. The control device 31 sets an alternating voltage with an amplitude that corresponds to the it frequency of the alternating voltage. It also corrects the amplitude value of the DC voltage, which is proportional to the amplitude value of the AC voltage.
Frequenzverschiebungen der Wechselεpannung werden auf diese Weise erfaßt und die sich darauε ergebenden Ände¬ rungen im Maεsenspektrum werden kompenεiert. Die Re¬ cheneinheit und der Frequenzzähler können Beεtandteil eineε einzigen Mikroprozessorε εein und lassen sich kostengünεtig aufbauen. Frequency shifts in the AC voltage are detected in this way and the resulting changes in the mass spectrum are compensated for. The computing unit and the frequency counter can be part of a single microprocessor and can be constructed inexpensively.

Claims

PATENTANSPRÜCHE PATENT CLAIMS
1. Quadrupol-Massenfilter mit1. Quadrupole mass filter with
vier konzentrisch parallel zueinander angeordneten Elektroden (1,1',3,3'),four electrodes (1,1 ', 3,3') arranged concentrically parallel to each other,
einer Wechselεpannungsquelle (15-27) für jedes Paar gegenüberliegender Elektroden, die eine -hoch¬ frequente Wechselspannung variabler Amplitude lie¬ fert, wobei die Elektroden (1,1 ',3,3') ein elek¬ trisches Feld erzeugen, durch das in Abhängigkeit von der Frequenz und der Amplitude der Wechsel¬ εpannung Ionen einer beεtim ten Maεse fokussiert werden, undan alternating voltage source (15-27) for each pair of opposing electrodes, which supplies a high-frequency alternating voltage of variable amplitude, the electrodes (1, 1 ', 3, 3') generating an electrical field through which in Depending on the frequency and the amplitude of the alternating voltage, ions of a specific mass are focused, and
einer Steuereinrichtung zur Einstellung der Ampli¬ tude der Wechselspannung,a control device for setting the amplitude of the AC voltage,
d a d u r c h g e k e n n z e i c h n e t ,characterized ,
daß eine Ko penεationεeinrichtung (33) vorgeεehen ist, die eine die Ist-Frequenz der Wechselεpannung meεsende Frequenzmeßeinrichtung (35) zur Feststel¬ lung einer Frequenzabweichung von der Soll-Fre¬ quenz der Wechselspannung aufweist, und daß die Kompenεationεeinrichtung (33) den für die Fokus- εierung der Ionen vorgegebenen Amplitudenwert der Wechselspannung in Abhängigkeit von der Frequenz¬ abweichung verändert. that a compensation device (33) is provided, which has a frequency measuring device (35) measuring the actual frequency of the alternating voltage for determining a frequency deviation from the desired frequency of the alternating voltage, and that the compensating device (33) has that for the Focusing of the ions predetermined amplitude value of the alternating voltage changes as a function of the frequency deviation.
2. Massenfilter nach Anspruch 1, dadurch gekennzeich¬ net, daß die Kompensationseinrichtung (33) eine Recheneinheit (37) aufweist, die das Produkt aus dem Amplitudenwert der Wechselspannung, der für die Fokusεierung der Ionen bei der Soll-Frequenz der Wechεelspannung vorgegeben ist, und einem Kor¬ rekturfaktor bildet, der εich aus dem Quotienten der Quadrate der gemesεenen Iεt-Frequenz und der Soll-Frequenz der Wechεelεpannung berechnet-, und daß die Steuereinrichtung (33) die Amplitude der Wechεelεpannung so einεtellt, daß der Amplituden¬ wert gleich dem ermittelten Produkt ist.2. mass filter according to claim 1, characterized gekennzeich¬ net that the compensation device (33) has a computing unit (37) that the product of the amplitude value of the AC voltage, which is predetermined for the focusing of the ions at the target frequency of the AC voltage, and forms a correction factor, which is calculated from the quotient of the squares of the measured actual frequency and the target frequency of the alternating voltage, and that the control device (33) adjusts the amplitude of the alternating voltage such that the amplitude value equals determined product is.
3. Massenfilter nach Anspruch 1 oder 2, dadurch ge¬ kennzeichnet, daß die Wechselspannungsquelle (15-27) einen freischwingenden Oszillator auf¬ weist.3. mass filter according to claim 1 or 2, characterized ge indicates that the AC voltage source (15-27) has a free-running oscillator.
4. Massenfilter nach einem der Anεprüche 1-3, dadurch gekennzeichnet, daß für jedeε Paar gegenüberlie¬ gender Elektroden (1,1' und 3,3') eine Gleichspan- nungεquelle (19) vorgeεehen iεt, die eine Gleich- εpannung variabler Amplitude liefert.4. Mass filter according to one of claims 1-3, characterized in that for each pair of opposing electrodes (1, 1 'and 3, 3') a DC voltage source (19) is provided which has a DC voltage of variable amplitude delivers.
5. Massenfilter nach einem der Anεprüche 1-4, dadurch gekennzeichnet, daß die Frequenzmeßeinrichtung (35) ein digitaler Frequenzzähler iεt. 5. Mass filter according to one of claims 1-4, characterized in that the frequency measuring device (35) is a digital frequency counter.
PCT/EP1993/003532 1992-12-17 1993-12-14 Quadrupole mass filter WO1994014184A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DEP4242766.5 1992-12-17
DE19924242766 DE4242766A1 (en) 1992-12-17 1992-12-17 Quadrupole mass filter

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DE10359367A1 (en) * 2003-12-18 2005-07-21 Inficon Gmbh Four pole filter for use in a mass spectrometer has capacitor circuit with a feedback loop control operation
DE102010004649B4 (en) 2010-01-13 2013-11-07 Inprocess Instruments Gmbh A radio frequency (RF) power supply system and method for supplying a multipole mass spectrometer with the RF AC voltage used to generate a multipole field
CN107968034B (en) * 2017-11-29 2024-03-01 宁波盘福生物科技有限公司 Stacked ring ion transmission device

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0488746A2 (en) * 1990-11-30 1992-06-03 Shimadzu Corporation Quadrupole mass spectrometers
WO1993008590A1 (en) * 1991-10-24 1993-04-29 Fisons Plc Power supply for multipolar mass filter

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SU957318A1 (en) * 1980-01-28 1982-09-07 Ордена Трудового Красного Знамени Специальное Конструкторское Бюро Аналитического Приборостроения Научно-Технического Объединения Ан Ссср Quadruple mass spectrometer

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0488746A2 (en) * 1990-11-30 1992-06-03 Shimadzu Corporation Quadrupole mass spectrometers
WO1993008590A1 (en) * 1991-10-24 1993-04-29 Fisons Plc Power supply for multipolar mass filter

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