Method and Apparatus for Tandem Time-of-Flight Mass Spectrometry

A method of tandem time-of-flight mass spectrometry implemented by a tandem time-of-flight mass spectrometer having:

• an ion source for ionizing a sample by irradiating it with pulsed laser light to generate ions, acceleration means for extracting the generated ions in a pulsed manner and accelerating the ions by a pulsed accelerating voltage under certain delayed extraction conditions, a first time-of-flight ion optical system permitting the accelerated ions to travel, an ion gate for selecting only ions having a desired mass-to-charge ratio as precursor ions from among the ions mass-separated by the first time-of-flight ion optical system, fragmentation means for fragmenting the selected precursor ions into product ions, a second time-of-flight ion optical system disposed behind the fragmentation means and permitting the product ions to travel, and a detector for detecting ions passed through the second time-of-flight ion optical system, said method comprising the steps of:
• drawing up a data table in preparation for measurements of product ions which are generated by selecting desired precursor ions by the ion gate and fragmenting the precursor ions, the table storing measured optimum values of delayed extraction conditions for the mass-to-charge ratios of plural reference substances and measured optimum values of the time for which the ion gate is opened;
• finding delayed extraction conditions and open time of the ion gate which optimize mass resolution at the mass-to-charge ratio of the desired precursor ions based on values stored in the table;
• and
• setting the found optimum values of the delayed extraction conditions and ion gate open time into the tandem time-of-flight mass spectrometer.