Orthogonal acceleration time-of-flight mass spectrometer and tuning method for the same

1 . An orthogonal acceleration time-of-flight mass spectrometer, comprising:

an ion source;

an orthogonal acceleration electrode configured to deflect a flight direction of ions incident from the ion source;

a flight-path-defining electrode configured to define a flight path of the ions deflected by the orthogonal acceleration electrode;

an ion detection section configured to detect an ion after a flight of the ion through the flight path is completed;

a voltage application section configured to apply a pulse voltage which deflects the flight direction of the ions in a predetermined cycle of time, as well as a standby voltage during other periods of time to the orthogonal acceleration electrode, and a voltage to the flight-path-defining electrode;

a measurement control section configured to acquire a plurality of mass spectrum data which are different in an intensity of a mass peak and a mass-resolving power in the mass spectrum data by conducting a measurement of a predetermined kind of known ion generated from a predetermined amount of known sample, under a plurality of measurement conditions which differ from each other in a value of the standby voltage applied from the voltage application section to the orthogonal acceleration electrode; and

a score-value calculation section configured to calculate a score value based on a predetermined calculation formula, using the intensity of the mass peak and the mass-resolving power in the mass spectrum data acquired under each of the plurality of measurement conditions.

2 . The orthogonal acceleration time-of-flight mass spectrometer according to claim 1 , wherein the measurement control section acquires mass spectrum data by performing a measurement of the known ion under a plurality of measurement conditions which differ from each other in a value of the voltage applied to the flight-path-defining electrode.

3 . The orthogonal acceleration time-of-flight mass spectrometer according to claim 1 , further comprising a tuning condition setting section configured to receive an input of a factor for the intensity of the mass peak and a factor for the mass-resolving power,

wherein the score-value calculation section calculates the score value as a sum of a value obtained by multiplying an intensity parameter value calculated from the intensity of the mass peak by the factor for the intensity of the mass peak and a value obtained by multiplying a resolving-power parameter value calculated from the mass-resolving power by the factor for the mass-resolving power.

4 . The orthogonal acceleration time-of-flight mass spectrometer according to claim 3 , wherein the intensity parameter value is a value normalized with reference to the value of the intensity of a largest mass peak among the mass spectrum data acquired under the plurality of measurement conditions, and the resolving-power parameter value is a value normalized with reference to the value of a highest mass-resolving power among the mass spectrum data acquired under the plurality of measurement conditions.

5 . A tuning method for an orthogonal acceleration time-of-flight mass spectrometer, comprising steps of:

generating a predetermined kind of known ion from a sample by an ion source;

deflecting a flight direction of ions incident from the ion source by applying, to an orthogonal acceleration electrode:

a pulse voltage during a predetermined cycle of time, so as to cause the ions to fly in a flight path defined by a flight-path-defining electrode; and

a standby voltage during other periods of time;

acquiring a plurality of mass spectrum data which are different in an intensity of a mass peak and a mass-resolving power in the mass spectrum data by detecting, under a plurality of measurement conditions which differ from each other in a value of the standby voltage, ions separated from each other by mass while flying in the flight path; and

calculating a score value based on a predetermined calculation formula, using the intensity of the mass peak of the known ion and the mass-resolving power in the mass spectrum data, where:

the score value is calculated for each of the plurality of measurement conditions; and

the value of the standby voltage to be applied to the orthogonal acceleration electrode is determined based on the score value calculated for each of the plurality of measurement conditions.

6 . The orthogonal acceleration time-of-flight mass spectrometer according to claim 1 , wherein the plurality of measurement conditions constitutes a first plurality of measurement conditions, and

wherein the measurement control section is further configured to acquire mass spectrum data by conducting a measurement of the predetermined kind of known ion generated from a predetermined amount of known sample, sequentially:

under a second plurality of measurement conditions which differ from each other in a value of the pulse voltage applied from the voltage application section to the flight-path-defining electrode, and

under the first plurality of measurement conditions which differ from each other in a value of the pulse voltage applied from the voltage application section to the orthogonal acceleration electrode.

7 . The orthogonal acceleration time-of-flight mass spectrometer according to claim 6 , wherein, after the acquiring mass spectrum data under the first plurality of measurement conditions, the measurement control section is further configured to acquire mass spectrum data by conducting a measurement of the predetermined kind of known ion generated from a predetermined amount of known sample under a third plurality of measurement conditions which differ from each other in a value of the pulse voltage applied from the voltage application section to the flight-path-defining electrode.

8 . The orthogonal acceleration time-of-flight mass spectrometer according to claim 1 , wherein

the plurality of the measurement conditions include a measurement condition in which the standby voltage is set such that at least a portion of ions, among the ions incident on the orthogonal acceleration electrode, having a flight component in an opposite direction to a direction in which the ions are deflected by the orthogonal acceleration electrode, are eliminated by colliding with the orthogonal acceleration electrode.