301. multiple heartcutting 2D separation In this mode of 2D-LC separation, several selected regions of the first separation are selected for further resolution by transferring the fluid exiting the first separation during several short (e.g., a few seconds to about a minute) intervals to the second separation column for further separation of sample constituents that were not initially separated by the first column.
302. multiple reaction monitoring (MRM) A quantification strategy generally used in triple quadrupole (QqQ) mass spectrometers in which an analyte ion with a particular mass-to-charge ratio (the precursor ion), most often corresponding to the intact ion of a target analyte, is selected by a first quadrupole (Q1) in the mass spectrometer. The precursor ions are then subjected to a collision-induced dissociation reaction with neutral gas, resulting in the formation of product ions, each with a particular mass-to-charge ratio, which are selected in another quadrupole (Q3) and subsequently detected.
