Multiple stage mass spectrometry: the next generation tandem mass spectrometry experiment

Tandem mass spectrometry has become a powerful tool for basic and applied mass spectrometry studies. Mass spectrometers based on ion trapping techniques, such as the quadrupole ion trap, have some unique capabilities as tandem mass spectrometers. Of particular note are the high MS–MS efficiency, the ability to perform multiple stages of tandem spectrometry (MSn), and the ability to effect ion–molecule reactions as part of the experimental sequence. This paper discusses the MSn experiment in a quadrupole ion trap and provides several examples of MSn experiments in which ion–molecule reactions are incorporated as one or more steps in the experiment. Examples include one in which MSn is used to determine the structure of an ion–molecule reaction product, one that involves multiple stages of collision-induced dissociation to generate a 13C containing reactant ion for an isotopic study, and one in which ion–molecule reactions are used to differentiate isomeric ion structures.