Mass spectrometer and mass spectrometry method

A method for performing a liquid chromatograph mass spectrometry for an ion generated from a liquid sample containing one or a plurality of components separated from each other in a column of a liquid chromatograph in an ionization source provided in a mass spectrometer, the ionization source including an ESI source for ionizing the liquid sample by applying an ESI voltage to an ESI probe into which the liquid sample is introduced and an APCI source for ionizing the liquid sample discharged from the ESI probe by applying an APCI voltage to a corona needle located near an exit port of the ESI probe, the method comprising steps of:

• a) allowing an analysis operator to set a plurality of ionization conditions for an ionization of the liquid sample, with the ionization conditions differing from each other in a value of the ESI voltage or/and a value of the APCI voltage;
• b) performing a mass spectrometry for an ion generated from the one or the plurality of components using the plurality of ionization condition cyclically and obtaining a plurality of mass chromatograms each of which corresponds to each of the plurality of ionization conditions;
• and
• c) selecting, for each of the one or the plurality of components, a mass spectrometry result in which the ion is detected with a suitable level of intensity for an analysis, from the mass spectrometry results respectively obtained for the plurality of ionization conditions based on the plurality of mass chromatograms.