Science Beu Consulting

Los Indios, TX, United States

Science Beu Consulting

Los Indios, TX, United States

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Ruddy B.M.,Florida State University | Beu S.C.,Science Beu Consulting | Kaiser N.K.,Florida State University | Hendrickson C.L.,Florida State University | Marshall A.G.,Florida State University
International Journal of Mass Spectrometry | Year: 2011

Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry relies upon linearity between the ion cyclotron excitation and the observed response. However, nonlinearities result from non-ideal applied electric and magnetic fields and Coulombic interactions. Here, we report nonlinear response at low excitation electric field magnitude due to Coulombic shielding. The measured ICR signal magnitude exhibits an excitation voltage threshold that increases monotonically with the number of shielding ions (i.e., unexcited ions). If shielding ions are not present, ICR signal magnitude versus excitation voltage is linear (e.g., for quadrupole-isolated ions of nearly a single m/z). Finally, we show that shielding results in a reduced cyclotron radius at low excitation voltage, resulting in an increased rate of transient decay; thereby exacerbating response nonlinearity and excitation threshold for long data acquisition period. © 2010 Elsevier B.V. All rights reserved.


Marshall A.G.,Florida State University | Blakney G.T.,Florida State University | Beu S.C.,Science Beu Consulting | Hendrickson C.L.,Florida State University | And 4 more authors.
European Journal of Mass Spectrometry | Year: 2010

Within a relative abundance dynamic range of ̃10,000 : 1, the world's most compositionally complex organic mixture is petroleum crude oil. As such, it provides the most challenging target for mass spectral resolution and identification of molecules below m/z 2000. The mass "splits" in petroleum include most of those that also appear in proteomics, metabolomics and other complex organic mixture analysis. Therefore, petroleum provides an excellent test bed for optimizing mass spectrometer performance in general. The presence of multiple elemental compositions spanning less than 1 Da in mass facilitates mapping and correction of rf phase variation across a Fourier transform ion cyclotron resonance mass spectrum, as well as exposing otherwise inaccessible systematic mass deviations, for additional improvement in mass resolving power and mass accuracy by a factor of up to 5. Internal mass calibration, combined with systematic peak assignment for successive homologous series, enables automated elemental composition assignment of tens of thousands of peaks in a single mass spectrum. © IM Publications LLP 2010.

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