Mass Spectrometry Forum: Chemical Noise in Mass Spectrometry Part III — More Mass Spectrometry/Mass Spectrometry

摘要

In the first installment of this four-part series on chemical noise in mass spectrometry (MS), attributes of MS/MS that reduce the contribution of chemical noise in a mass spectral measurement were discussed in broad terms. In particular, use of sequential stages of analysis, in which each stage exhibits a greater discrimination against noise than signal, was shown to result in an increased signal-to-noise ratio (S/N) in the final measurement. Implicit in this initial discussion was the assumption that a discriminating factor between signal and noise could be found and exploited, and of course, the better the discriminant, the fewer stages of sequential analysis are needed to achieve the desired S/N. In the second column in this series (2), the effects of the ionization method selected on chemical noise levels were discussed. It was shown that the traits of the ionization method itself could be used as a discriminant against chemical noise. Chemical ionization was used as an example of an ionization method that can reduce chemical noise observed in a mass spectrum, and fast atom bombardment (FAB) and matrix-assisted laser desorption ionization were presented as examples of ionization methods that, as a direct consequence of how they work, usually actually increase the level of chemical noise. In this third installment within the series, we now discuss examples of chemical ionization and FAB in conjunction with MS/MS to explore in greater detail how and why chemical noise is reduced. The approach again emphasizes basic overarching principles rather than numerous applications.