Quadrupole mass filters and mass analysers
AssigneeMicromass UK Limited
InventorsDavid J. Langridge, David Gordon
Life of this patent
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Abstract
A method of mass spectrometry comprising: supplying ions having an initial range of axial kinetic energies towards a mass filter; and mass filtering the ions by applying different voltages to electrodes of the mass filter during different respective dwell times so as to provide different mass transmission windows during the different dwell times; wherein the method comprises increasing the range of axial kinetic energies that the ions have, as they pass towards and/or through the mass filter, during at least one of the dwell times.
Claims25
A method of mass spectrometry comprising:
- supplying ions having an initial range of axial kinetic energies towards a mass filter;
- and
- mass filtering the ions by applying different voltages to electrodes of the mass filter during different respective dwell times so as to provide different mass transmission windows during the different dwell times;
- wherein the method comprises increasing the range of axial kinetic energies that the ions have, as they pass towards and/or through the mass filter, during at least one of the dwell times.
The method of any preceding claim, comprising providing a physical aperture, or an ion-optical device having an ion acceptance aperture defined by electric fields of the ion-optical device, downstream of the mass filter for receiving ions transmitted by the mass filter.
The method of any preceding claim, comprising detecting the ions transmitted during said different dwell times, or fragment or product ions thereof, downstream of the mass filter so as to generate mass spectral data, and summing the mass spectral data obtained over said different dwell times;
- optionally so as to form at least one mass peak corresponding to ions transmitted by the mass filter during said different dwell times, or for the fragment or product ions thereof.
The method of any preceding claim, wherein said step of increasing the range of axial kinetic energies comprises performing a plurality of cycles during each of said at least one of the dwell times, wherein each cycle comprises modulating the axial kinetic energy of the ions passing towards and/or through the mass filter between a minimum axial kinetic energy and a maximum axial kinetic energy.
The method of any preceding claim, wherein said step of increasing the range of axial kinetic energies that the ions have comprises:
- providing the ions that reach the exit of the mass filter, over the course of one of the dwell times, with a first range of axial kinetic energies that are distributed about a first average axial kinetic energy;
- and
- providing the ions that reach the exit of the mass filter, over the course of another of the dwell times, with a second range of axial kinetic energies that are distributed about a second average axial kinetic energy;
- wherein the second range of axial kinetic energies is wider than the first range of axial kinetic energies, and the second average axial kinetic energy is higher than the first average axial kinetic energy.
The method of any preceding claim, wherein said step of increasing the range of axial kinetic energies comprises providing a DC potential difference along an axial region of the mass filter, or along an axial region upstream of the mass filter, and varying the DC potential difference during each of said at least one of the dwell times such that ions entering said axial region at different times are imparted with different axial kinetic energies.
The method of any preceding claim, comprising increasing the range of axial kinetic energies of the ions, as they pass towards and/or through the mass filter, so that the ions have a first range of axial kinetic energies during a first of said dwell times, during which the mass filter has a mass transmission window set to transmit ions in a first range of mass to charge ratios;
- wherein the method further comprises:
- (i) increasing the range of axial kinetic energies of the ions, as they pass towards and/or through the mass filter, so that the ions have a second range of axial kinetic energies that is narrower than said first range of axial kinetic energies during a second of said dwell times, during which the mass filter has a mass transmission window set to transmit ions in a second range of mass to charge ratios that is higher than said first range of mass to charge ratios;
- and/or
- (ii) not increasing the range of axial kinetic energies of the ions, as they pass towards and/or through the mass filter, during a dwell time at which the mass filter has a mass transmission window set to transmit ions in a range of mass to charge ratios that is higher than the first and/or second range of mass to charge ratios.
The method of any preceding claim, comprising providing the ions with a first average axial kinetic energy through the mass filter during a dwell time at which the mass filter has a mass transmission window set to transmit ions in one range of mass to charge ratios;
- and
- providing the ions with a second average axial kinetic energy through the mass filter, that is lower than the first average axial kinetic energy, during a dwell time at which the mass filter has a mass transmission window set to transmit ions in a range of mass to charge ratios that is higher than said one range of mass to charge ratios.
A mass spectrometer comprising:
- a mass filter having electrodes;
- at least one voltage supply for applying voltages to the electrodes;
- and
- control circuitry configured to control the mass spectrometer to:
- supply ions having an initial range of axial kinetic energies towards the mass filter;
- control the at least one voltage supply to apply different voltages to electrodes of the mass filter during different respective dwell times so as to provide the mass filter with different mass transmission windows during the different dwell times;
- and
- increase the range of axial kinetic energies that the ions have, as they pass towards and/or through the mass filter, during at least one of the dwell times.
A method of mass spectrometry comprising:
- supplying ions towards a mass filter having a mass transmission window;
- and
- increasing the range of axial kinetic energies that the ions have as they pass towards and/or through the mass filter.
A mass spectrometer comprising:
- a mass filter having electrodes;
- at least one voltage supply for applying voltages to the electrodes so as to provide the mass filter with a mass transmission window;
- and
- control circuitry configured to control the mass spectrometer to:
- supply ions towards the mass filter;
- and
- increase the range of axial kinetic energies that the ions have as they pass towards and/or through the mass filter.
A method of mass spectrometry comprising:
- (i) mass filtering ions using a mass filter having a mass transmission window;
- (ii) repeatedly scanning the mass transmission window across a range of mass to charge ratios that has a width of less than 1 Da.
A method of mass spectrometry comprising:
- (i) mass filtering ions using a mass filter having a mass transmission window;
- (ii) varying the width of the mass transmission window whilst the centre of the mass transmission window is maintained at a constant mass to charge ratio value.
Dependencies are inferred from the claim text.