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Molecular Structure from Molecular Mass

Molecular Structure from Molecular Mass

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Molecular Structure from Molecular Mass

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  1. Jeremiah M. Purcella, Ryan P. Rodgersa,b,*, Christopher L. Hendrickson,a,c and Alan G. Marshalla,b,* Molecular Structure from Molecular Mass a Dept. of Chemistry and Biochemistry, Florida State Univ., Tallahassee, FL 32306, USA bIon Cyclotron Resonance Program,National High Magnetic Field Laboratory, Tallahassee, Florida 32310-4005, USA The smallest chemically distinct unit of matter is a molecule. High-resolution mass spectrometry can determine the chemical formula of a molecule: i.e., its number and types of constituent atoms, e.g., CcHcNnOoSs. However, mass alone cannot usually determine how the atoms are linked together in the molecular structure. NHMFL/FSU researchers have recently shown that ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) can differentiate molecules containing a nitrogen atom in a five-member vs. six-member aromatic ring (as in crude oil). Atmospheric pressure photoionization distinguishes the two kinds of rings in a single positive-ion mass spectrum [see Figure: a five-member ring yields M+ ions, whereas a six-member ring yields (M+H)+ ions]. High magnetic field FT-ICR MS is required, because it is necessary to resolve molecules differing in mass by less than 0.005 of the mass of the smallest atom (hydrogen). *Supported by NSF (DMR-00-84173), NHMFL, & Florida State U. Purcell, J. M.; Rodgers, R. P.; Hendrickson, C. L.; Marshall, A. G. "Speciation of Nitrogen Containing Aromatics by Atmospheric Pressure Photoionization or Electrospray Ionization Fourier Transform Ion Cyclotron Resonance Mass Spectrometry," J. Am. Soc. Mass Spectrom.2007, 18, 1265-1273 .