Mass spectrometer and method of analyzing isomers

A mass spectrometer comprising:

• an MSn analysis unit that ionizes a sample eluted from a separation unit that separates the sample into individual components, fragment an ion of a desired mass number, and perform a mass analysis of fragment ions;
• a first database storing retention time information for each of a plurality of compounds;
• and
• a second database storing correlation information between an ion intensity ratio of fragment ions of a mixture of isomers and an isomer presence ratio of said isomers in said mixture per isomer,
• wherein said databases are used to determine whether the samples contains isomers, and to calculate the presence ratio between the isomers if the samples contains the isomers.

A method of analyzing isomers by using a separation unit that separates a sample into individual components and a mass spectrometer with an MSn analysis unit that fragment an ion of a desired mass number and perform a mass analysis of fragment ions, said mass spectrometer including a first database storing retention time information for each of a plurality of compounds, a second database storing correlation information between an ion intensity ratio of fragment ions of a mixture of isomers and an isomer presence ratio of said isomers in said mixture per isomer, and a third database storing MS2 spectra of the plurality of compounds, said method comprising the steps of:

• obtaining a mass spectrum with an MS2 analysis of the sample;
• searching said third database based on the obtained mass spectrum, and computing similarity between the obtained mass spectrum and each of the compounds in said third database;
• searching said first database to check the retention time of each of the compounds for which similarity has been computed, and finding the compounds having the same retention time;
• and
• determining the compounds having the same retention time to be isomers, and computing an isomer presence ratio based on the obtained mass spectrum by using said second database.