Mass spectrometer

Patent metadata

Field	Value
Publication number	US-10705048-B2
Application number	US-201616320673-A
Country	US
Kind code	B2
Filing date	Jul 27, 2016
Priority date	Jul 27, 2016
Publication date	Jul 7, 2020
Grant date	Jul 7, 2020

Abstract

When a normal mass spectrometry is performed without dissociating an ion, the m/z range limitation voltage setting unit applies a radio-frequency voltage to each rod electrode of the quadrupole mass filter and controls the quadrupole voltage generator so as to apply a direct current voltage smaller than that at the time of ion selection for MS/MS spectrometry. When a small direct current voltage is applied, a mass scanning line is set so as to pass through a stability region on a Mathieu diagram over a long range, hence large m/z ions that do not fall within the stability region are blocked in the quadrupole mass filter. By adjusting a cut-off point on larger m/z side blocked in accordance with the measurement period of OA-TOFMS including the orthogonal accelerator, heavy ions that cause period delay are prevented from being introduced into the orthogonal accelerator.

First claim

The invention claimed is:

1. A mass spectrometer comprising:
an ion source configured to ionize a sample component;
a time-of-flight mass spectrometry unit that repeatedly performs mass spectrometry in a predetermined measurement period and includes:
a flight space in which ions fly,
an ejection unit that gives a predetermined energy to ions generated in the ion source or ions derived from the ions and ejects the ions towards the flight space, and
a detector configured to detect ions having flown in the flight space;

an ion transport unit that includes a multipole electrode provided between the ion source and the ejection unit;
a voltage generator configured to apply, to the multipole electrode, a voltage, obtained by adding a radio-frequency voltage and a direct current voltage, for forming a multipole electrical field in which ions within a range of equal to or larger than a predetermined mass-to-charge ratio with which the time of flight in the flight space exceeds at least the predetermined measurement period when ions pass through a space surrounded by the multipole electrodes are diffused; and
a control unit configured to control the voltage generator in such a manner that an inclination of a mass scanning line set so as to pass an origin and through a stability region on a Mathieu diagram where a “q” value and an “a” value, which are parameters based on a Mathieu equation, are adopted for the two axes is changed in accordance with mass scanning over a mass-to-charge-ratio range of a measurement target and that a direct current voltage and a radio-frequency voltage changing in response to a change in the inclination of the mass scanning line are applied to the multipole electrode,
wherein: the control unit changes a direct current voltage in accordance with scanning of the radio-frequency voltage in such a manner that the upper limit of the mass-to-charge ratio of ions passing through the ion transport unit is maintained approximately constantly; and
heavy ions with a mass-to-charge ratio above the mass-to-charge ratio upper limit are blocked in accordance with the predetermined measurement period such that the heavy ions that cause period delay are prevented from being introduced into the ejection unit.

2. The mass spectrometer according to claim 1 , further comprising:
a quadrupole mass filter selectively allowing an ion having a specific mass-to-charge ratio to pass through; and
a collision cell used for dissociating an ion provided between the quadrupole mass filter and the ejection unit,
wherein the quadrupole mass filter is used as the ion transport unit.

3. A mass spectrometer comprising:
an ion source configured to ionize a sample component;
a quadrupole mass filter capable of selecting an ion having a specific mass-to-charge ratio among ions generated in the ion source;
a collision cell configured to dissociate the ion selected in the quadrupole mass filter;
a time-of-flight mass spectrometry unit that includes
a flight space in which ions fly,
an ejection unit that gives a predetermined energy to ions generated in the ion source or ions generated by ion dissociation in the collision cell and ejects the ions towards the flight space, and
a detector configured to detect ions having flown in the flight space

a voltage generator that applies, to each electrode of the quadrupole mass filter, a voltage obtained by adding a radio-frequency voltage and a direct current voltage; and
a control unit configured to control the voltage generator in order to change a direct current voltage in accordance with scanning of the radio-frequency voltage in such a manner that an inclination of a mass scanning line that is a straight line passing through an origin on a Mathieu diagram where a “q” value and an “a” value, which are parameters based on a Mathieu equation, are adopted for two axes is adjustable within a predetermined range between a horizontal state where a=0 and a predetermined inclination state where the mass scanning line passes through a base of a stability region, and that the upper limit of the mass-to-charge ratio of ions passing through the quadrupole mass filter is maintained approximately constantly,
wherein, heavy ions with a mass-to-charge ratio above the mass-to-charge ratio upper limit are blocked in accordance with the predetermined measurement period such that the heavy ions that cause period delay are prevented from being introduced into the election unit.

4. The mass spectrometer according to claim 3 , selectably including, as operation modes of the quadrupole mass filter:
a first mode in which the inclination of the mass scanning line is set such that, on the Mathieu diagram, the mass scanning line passes through a predetermined range near a top of a stability region; and
a second mode in which, on the Mathieu diagram, the inclination of the mass scanning line is adjustable within a predetermined range between a horizontal state and the predetermined inclination state, and a direct current voltage is changed in accordance with scanning of the radio-frequency voltage in such a manner that the upper limit of the mass-to-charge ratio of ions passing through the quadrupole mass filter is maintained approximately constantly,
wherein the control unit controls the voltage generator in order to change each of a radio-frequency voltage and a direct current voltage in such a manner that the inclination of the mass scanning line is gradually changed in accordance with scanning of mass-to-charge ratio from a mass scanning line with a designated inclination when the second mode is selected.

Assignees

• Shimadzu Corp

Inventors

• Okumura Daisuke

Classifications

• H01J49/401 Primary

  characterised by orthogonal acceleration, e.g. focusing or selecting the ions, pusher electrode · CPC title

• H01J49/429

  Scanning an electric parameter, e.g. voltage amplitude or frequency · CPC title

• H01J49/4215

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

• G01N27/62 Primary

  by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode · CPC title