Precursor ions, higher-charged

Schwartz and co-workers have proposed a modified notch isolation method that has somewhat higher resolution [39,40], The method combines a notch waveform with slow RF resonance ejection scanning. In the first step of the method, most of the unwanted ions, except the precursor and ions of mass/charge ratio similar to that of the precursor ions, are ejected by a notch waveform. The trapping RF is then scanned slowly down to eject ions with m/z-values higher than that of the precursor ions. Next, the trapping RF is ramped slowly up to eject ions with m/z-values lower than that of the precursor ions. An isolation resolution. Am, of ca 0.3 Th has been demonstrated with the technique. 

An accurate description of the processes that result in the binding of ionic ligands to substrates used for catalyst supports is a requisite step to develop a basis for catalyst preparation. Few will dispute that strong binding of catalytic precursor ions to catalyst supports will result in a resistance to sintering and a higher dispersion of the active phase. If the view of electrostatic attraction between the catalytic precursor ion and the charge present on the surface is accepted, then the chemically induced/spatially defined architecture present on the support becomes the "traffic cop" which directs the potential fate of the structure of the finished catalyst. 

In situations where it is desirable to preferentially form analyte ions of higher charge state—for example, to obtain more reactive precursors for tandem mass spectrometry experiments or to improve the efficiency of electron capture in either electron capture dissociation (ECD) or electron transfer dissociation (ETD) experiments—then the use of narrow diameter capillaries is recommended. Conversely, if lower charge states are desirable, such as singly charged small molecule precursor ions that present more straightforward spectral interpretation, then wider diameter capillaries are preferable. ... 

---