Method of Calibrating a Mass Spectrometer

Patent metadata

Field	Value
Publication number	US-2018047549-A1
Application number	US-201715675125-A
Country	US
Kind code	A1
Filing date	Aug 11, 2017
Priority date	Aug 12, 2016
Publication date	Feb 15, 2018
Grant date	—

Abstract

A method of calibrating a mass spectrometer is disclosed. The mass spectrometer includes a first quadrupole, a second mass analyzer and a detection means. The method includes calibrating the second mass analyzer at a first time, calibrating the first quadrupole at a second time later than the first including a) determining for each of several selected masses a corresponding value of the amplitude of the RF voltage and DC voltage applied to the electrodes of the first quadrupole, b) fitting a function of the selected mass to the values of the amplitude of the RF voltage and DC voltage corresponding to the several selected masses, c) detecting the selected mass in a filter window width over a mass range, d) evaluating a shift of the peak position and/or a deviation of the filter window width, and e) repeating the calibration steps under certain conditions.

First claim

1 . A method for calibrating a mass spectrometer comprising an ion source, a first mass analyzer being a first quadrupole, a second mass analyzer and a detection means to detect ions, wherein ions ejected from the ion source can be moved on trajectories to the detection means passing both mass analyzers in which they first pass the first quadrupole and afterwards the second mass analyzer or vice versa, the first quadrupole operable as a pre-selecting mass analyzer in a mass selecting mode selecting masses in a mass filter window having a filter window width w, in which a RF voltage and a DC voltage are applied to electrodes of the first quadrupole, the amplitude of the RF voltage being a first function RF(m, w) of a selected mass m and the filter window width w and the DC voltage being a second function DC(m, w) of the selected mass m and the filter window width w comprising the steps:
i) calibrating the second mass analyzer at a first time t 1 , ii) calibrating the first quadrupole in the mass selecting mode selecting masses in the mass filter window having the filter window width w cal at a second time t 2 later than the first time t 1 when the second mass analyzer is operated in a mass analysing mode comprising the following steps: ii a) determining individually for each of several selected masses m cal a corresponding value of the amplitude of the RF voltage RF det (m cal ) and value of DC voltage DC det (m cal ) applied to the electrodes of the first quadrupole, ii b) fitting a function RF fit (m, w cal ) of the selected mass m to the values of the amplitude of the RF voltage RF det (m cal ) corresponding to the several selected masses m cal and fitting a function DC fit (m, w cal ) of the selected mass m to the values of DC voltages DC det (m cal ) corresponding to the several selected masses m cal , ii c) for some masses and/or at least some of the several selected masses m check detecting the selected mass m check at the detection means via the second analyzer operating in a mass analysing mode during scanning the first quadrupole operating as pre-selecting analyzer in the mass selecting mode selecting masses in the mass filter window having the filter window width w cal over a mass range ρ mass _ m _ check assigned to the mass m check , comprising the mass m check and being larger than the filter window width w cal of the mass filter window of the mass selecting mode of the first quadrupole, the amplitude of the RF voltage applied to the electrodes of the first quadrupole given by the function RF fit (m, w cal ) and the DC voltage applied to the electrodes of the first quadrupole given by the function DC fit (m, w cal ), ii d) evaluating for each of these detected masses m check a shift of the peak position Δm(m check ) and/or a deviation of the filter window width Δw(m check ) of the mass selecting mode of the first quadrupole selecting masses in the mass filter window having the filter window width w cal , when applying the RF voltage with the amplitude given by the function RF fit (m, w cal ) and the DC voltage given by the function DC fit (m, w cal ), ii e) if the evaluated values of the shift of the peak position Δm(m check ) and/or the deviation of the filter window width Δw(m check ) of the detected masses m check do not comply with a quality condition of the calibration or if another repetition condition is fulfilled, repeating the calibration steps ii a) to ii e) until all quality conditions of the calibration are fulfilled and no repetition condition is fulfilled or the calibration steps ii a) to ii e) have been executed N times.

2 . The method of claim 1 wherein the second mass analyzer is a second quadrupole, a time-of-flight mass analyser, an ion trap, an orbitrap, or an ion cyclotron resonance cell.

3 . The method of claim 2 wherein the mass spectrometer comprises a third quadrupole.

4 . The method of claim 3 wherein during the calibration of the first quadrupole in the mass selecting mode the third quadrupole is operated in a transmission mode.

5 . The method of claim 1 wherein the mass spectrometer further comprises a reaction cell, which is located between the first quadrupole and the second mass analyzer and is passed by the ions ejected from ion source which are moved on trajectories to the detection means.

6 . The method of claim 5 wherein the reaction cell is a collision and/or fragmentation cell.

7 . The method of claim 5 wherein the reaction cell comprises a quadrupole.

8 . The method of claim 1 wherein during the calibrating of the second mass analyzer (step i) the first quadrupole is operated in a transmission mode in which ions are not mass selected.

9 . The method of claim 1 wherein the first quadrupole is calibrated in the mass selecting mode to have a filter window width w cal between 2 u and 30 u.

10 . The method of claim 9 wherein the step ii) of calibrating the first quadrupole in the mass selecting mode is repeated several times for different values of the filter window width w cal in the range between 2 u and 30 u.

11 . The method of claim 1 wherein at the beginning of the calibration of the first quadrupole in the mass selecting mode an initial function RF ini (m, w cal ) for the first function RF(m, w cal ) and an initial function DC ini (m, w cal ) for the second function DC(m, w cal ) is used.

12 . The method of claim 1 wherein for two selected masses m coarse a corresponding value of the amplitude of the RF voltage RF det (m coarse ) and value of DC voltage DC det (m coarse ) is determined individually before for several selected masses m cal a corresponding value of the amplitude of the RF voltage RF det (m cal ) and value of DC voltage DC det (m cal ) is determined individually (step ii a)).

13 . The method of claim 12 wherein after for the two selected masses m coarse a corresponding value of the amplitude of the RF voltage RF det (m coarse ) and value of DC voltage DC det (m coarse ) is determined individually a function RF coarse (m, w cal ) being a summation of a constant value RFoffset 2 _ fit and a linear function of the selected mass m is fitted to the values of the amplitudes of the RF voltage RF det (m coarse ) corresponding to the two selected masses m coarse and/or a function DC coarse (m, w cal ) being a summation of a constant value DCoffset 2 _ fit and a linear function of the selected mass m is fitted to the values of DC voltages DC det (m coarse ) corresponding to the two selected masses m coarse .

14 . The method of claim 11 wherein after for the two selected masses m coarse a corresponding value of the amplitude of the RF voltage RF det (m coarse ) and value of DC voltage DC det (m coarse ) is determined individually a function RF coarse (m, w cal ) of the selected mass m is fitted to the values of the amplitudes of the RF voltage RF det (m coarse ) corresponding to the two selected masses m coarse by changing a linear factor RFlinear and/or a constant offset value RFoffset of the initial function RF ini (m, w cal ) and/or a function DC coarse (m, w cal ) of the selected mass m is fitted to the values of DC voltage DC det (m coarse ) corresponding to the two selected masses m coarse by changing a linear factor DClinear and/or a constant offset value DCoffset of the initial function DC ini (m, w cal ).

15 . The method of claim 1 wherein the several selected masses m cal , for which a corresponding value of the amplitude of the RF voltage RF det (m cal ) and value of DC voltage DC det (m cal ) is determined individually (step ii a)), are 4 to 18 selected masses m cal .

16 . The

Assignees

• Thermo Fisher Scient Bremen Gmbh

Inventors

• Quaas Norbert
• Schlueter Hans Juergen
• Jung Gerhard

Classifications

• H01J49/36

  Radio frequency spectrometers, e.g. Bennett-type spectrometers, Redhead-type spectrometers · CPC title

• H01J49/4215

  Quadrupole mass filters (H01J49/4225 takes precedence) · CPC title

• H01J49/4225

  Multipole linear ion traps, e.g. quadrupoles, hexapoles · CPC title

• H01J49/0009 Primary

  Calibration of the apparatus · CPC title

• H01J49/42 Primary

  Stability-of-path spectrometers, e.g. monopole, quadrupole, multipole, farvitrons · CPC title