SPECIAL FEATURE:TUTORIAL Slow Heating Methods in Tandem Mass Spectrometry

TLDR

Slow heating methods in tandem mass spectrometry, such as infrared multiphoton dissociation and blackbody radiation, enable ion activation and deactivation rates to be comparable, allowing steady‑state internal energy distributions and thermal‑dissociation kinetics, and are increasingly used for high‑mass ion dissociation. This perspective aims to frame slow heating methods by describing their thermal analogy, limiting energy exchange conditions, and shared figures of merit, and to discuss implications for dissociation rates and product ion spectra. The authors discuss the thermal analogy of slow heating, detailing rapid versus slow energy exchange limits and their effects on dissociation kinetics and product ion spectra. © 1997 by John Wiley & Sons, Ltd.

Abstract

Several approaches to ion activation in tandem mass spectrometry have been developed in recent years for use in ion trapping instruments that allow for conditions to be reached wherein rates of ion activation and deactivation are comparable. These approaches are defined as slow heating methods and include continuous-wave laser infrared multiphoton dissociation, dissociation driven by blackbody radiation, quadrupole ion trap collisional activation and sustained off-resonance irradiation in ion cyclotron resonance mass spectrometry. In the limiting case in which ion activation and deactivation rates are equal, a steady-state parent ion internal energy distribution is achieved and the kinetics of dissociation can be interpreted in analogy with thermal dissociation. This discussion describes the thermal analogy and the limiting conditions of rapid energy exchange and slow energy exchange along with the possible ramifications for dissociation rates and product ion spectra. The figures of merit that the various slow heating methods share as a class of activation methods are also discussed. The purpose of this perspective is to provide a frame-of-reference from which slow heating methods can be considered. Such methods are seeing increasing use as the number of ion trapping instruments grows and have shown remarkable success with dissociation of high-mass ions. © 1997 by John Wiley & Sons, Ltd.