mass spectrum SRM spectrum Spectrum obtained when data are acquired from specific product ions corresponding to m/z values of selected precursor ions a recorded via two or more stages of mass spectrometry. The precursor/product ion pair is called a transition pair. Data can be obtained for a single transition pair or multiple transition pairs. Multiple time segments of different transition pairs can exist in a single file. Single precursor ions can have multiple product ions consitituting multiple transition pairs. Selected reaction monitoring can be performed as tandem mass spectrometry in time or tandem mass spectrometry in space. MRM spectrum selected reaction monitoring spectrum MS multiple reaction monitoring spectrum MS:1000583