Time-of-flight mass spectrometer and time-of-flight mass spectrometry method
A TOFMS includes flight space formation electrodes, an ion detection unit, voltage switching units to switch a voltage to be applied to the flight space formation electrode from a first voltage for flying ions of a first polarity to a second voltage for flying ions of a second polarity, ion information acquisition units to obtain a time of flight or a m/z of the ions based on a detection result of the ions of the second polarity after the voltage has been switched, a correction information storage unit to store correction information related to a deviation in time of flight or a m/z associated with an elapsed time from the switching timing, and a correction unit to correct the flight time or the m/z according to an elapsed time from the switching timing when the detection result of the ion is obtained using the correction information.
1 . A time-of-flight mass spectrometer comprising:
a flight space formation electrode configured to form a flight space for separating ions derived from a component contained in a sample according to a mass-to-charge ratio;
an ion detection unit configured to detect ions that have flown in the flight space;
a voltage switching unit configured to switch a voltage to be applied to the flight space formation electrode from a first voltage for flying ions of a first polarity to a second voltage for flying ions of a second polarity at a given switching timing;
an ion information acquisition unit configured to obtain a time of flight during which the ion flies in the flight space or a mass-to-charge ratio of the ion based on a detection result of the ions of the second polarity obtained by the ion detection unit after the voltage has been switched by the voltage switching unit;
a correction information storage unit configured to store correction information related to a deviation in time of flight or a mass-to-charge ratio associated with an elapsed time from the switching timing; and
a correction unit configured to correct the time of flight or the mass-to-charge ratio obtained by the ion information acquisition unit according to an elapsed time from the switching timing when the detection result of the ion is obtained using the correction information stored in the correction information storage unit.
2 . The time-of-flight mass spectrometer according to claim 1 , wherein
the correction information is a correction value corresponding to an elapsed time from the switching timing, and
the correction unit is configured to add the correction value stored in the correction information storage unit to the time of flight or the mass-to-charge ratio obtained by the ion information acquisition unit.
3 . The time-of-flight mass spectrometer according to claim 1 , wherein
the correction information is a correction coefficient corresponding to an elapsed time from the switching timing, and
the correction unit is configured to multiply the time of flight or the mass-to-charge ratio obtained by the ion information acquisition unit by a correction coefficient stored in the correction information storage unit.
4 . The time-of-flight mass spectrometer according to claim 1 , further comprising a correction information acquisition unit which is configured to create or change the correction information.
5 . The time-of-flight mass spectrometer according to claim 4 further comprising an ion source which is configured to generate ions derived from components contained in the sample; and a sample introduction unit which is configured to introduce a known sample into the ion source, wherein
the correction information acquisition unit is configured to create or change the correction information based on a change in a time-of-flight or a mass-to-charge ratio over time from the switching timing obtained from an intensity signal of ions derived from the known sample.
6 . The time-of-flight mass spectrometer according to claim 4 , wherein the correction information acquisition unit is configured to store a model function corresponding to correction information related to an elapsed time from the switching timing and a deviation in time of flight or a mass-to-charge ratio, and create or change the correction information by changing a parameter value included in the model function.
7 . The time-of-flight mass spectrometer according to claim 6 , wherein
the model function includes, as a parameter, a value of at least one of electric resistance, inductance, or capacitance in a simplified circuit connected to a power supply unit that applies a voltage to the flight space formation electrode, and
the correction information acquisition unit is configured to acquire the correction information by changing at least one value of the parameter values included in the model function.
8 . The time-of-flight mass spectrometer according to claim 7 , wherein the model function is a voltage response function including values of electric resistance and capacitance in a simplified circuit connected to the power supply unit as parameters.
9 . The time-of-flight mass spectrometer according to claim 7 , wherein
the model function is a damped response function including at least a value of inductance in a simplified circuit connected to the power supply unit as a parameter, and
the correction information acquisition unit is configured to change the damped response function by changing the value of the inductance to acquire the correction information.
10 . The time-of-flight mass spectrometer according to claim 1 further comprising, an ion ejector configured to be controlled to perform a measurement event in which an operation of ejecting ions derived from a sample component into the flight space is periodically performed a plurality of times, wherein
the ion information acquisition unit is configured to obtain a time of flight in which the ions fly in the flight space or a mass-to-charge ratio of the ions based on a result of integrating or averaging intensity signals of the ions obtained for each of a plurality of ion emission operations performed in the measurement event, and
the correction unit is configured to correct the time of flight or the mass-to-charge ratio obtained by the ion information acquisition unit according to an elapsed time from the switching timing to the start of the measurement event and a predetermined delay time from the start of the measurement event.
11 . The time-of-flight mass spectrometer according to claim 10 , wherein the predetermined delay time is ½ of a time taken for the measurement event.
12 . The time-of-flight mass spectrometer according to claim 1 further comprising a voltage monitoring unit configured to acquire a monitor voltage corresponding to a voltage applied to the flight space formation electrode, wherein
the correction unit is configured to correct the time of flight or the mass-to-charge ratio obtained by the ion information acquisition unit according to an elapsed time from the switching timing and the monitor voltage.
13 . The time-of-flight mass spectrometer according to claim 1 , wherein an elapsed time from the switching timing is less than five seconds.
14 . The time-of-flight mass spectrometer according to claim 1 , wherein the flight space formation electrode includes a flight tube to which a high voltage with an absolute value of 1 kV or more is applied.
15 . The time-of-flight mass spectrometer according to claim 1 , wherein the flight space formation electrode includes a reflectron to which a high voltage with an absolute value of 500 V or more is applied.
16 . The time-of-flight mass spectrometer according to claim 1 , wherein the flight space formation electrode includes an electrode that forms a multi turn orbit in which ions turn around a plurality of times or a multi reflection orbit in which ions are reflected a plurality of times by an electric field.
17 . The time-of-flight mass spectrometer according to claim 1 , wherein the flight space formation electrode included an ion ejection electrode to which a high voltage having an absolute value of 1 kV or more is applied in a pulsed manner, and which ejects ions of the second polarity toward the flight space by the applied voltage.
18 . A time-of-flight mass spectrometry method comprising:
a voltage switching step of switching a voltage to be applied to a flight space formation electrode which is configured to form a flight space for separating ions derived from a component contained in a sample according to a mass-to-charge ratio, from a first voltage for flying ions of a first polarity to a second voltage for flying ions of a second polarity at a given switching timing;
an ion information acquisition step of obtaining a time of flight during which the ions fly in the flight space or a mass-to-charge ratio of the ions based on a detection result of the ions of the second polarity obtained by an ion detection unit which is configured to detect ions that have flown in the flight space after the voltage has been switched by the voltage switching step; and
a correction step of correcting the time of flight or the mass-to-charge ratio obtained in the ion information acquisition step according to an elapsed time from the switching timing when the detection result of the ion is obtained using correction information in which an elapsed time from the switching timing is associated with information on a deviation in the time of flight or the mass-to-charge ratio.