126 264 Assigned Chemical Formulas from an Atmospheric Pressure Photoionization 9.4 T Fourier Transform Positive Ion Cyclotron Resonance Mass Spectrum.

Abstract

Here, we present atmospheric pressure photoionization (APPI) Fourier transform ion cyclotron resonance (FTICR) mass analysis of a volcanic asphalt sample by acquiring data for 20 Da wide mass segments across a 1000 Da range, stitched into a single composite mass spectrum, and compare to a broad-band mass spectrum for the same sample. The segmented spectrum contained 170 000 peaks with magnitude greater than 6σ of the root-mean-square (rms) baseline noise, for which 126 264 unique elemental compositions could be assigned. Approximately two-thirds of those compositions represent monoisotopic (i.e., chemically different) species. That complexity is higher than that for any previously reported mass spectrum and almost 3 times greater than that obtained from the corresponding broad-band spectrum (59 015). For the segmented mass spectrum, the signal-to-noise ratio (S/N) was significantly higher throughout the spectrum, but especially at the lower and upper ends of mass distribution relative to that of the near-Gaussian broad-band mass distribution. Despite this S/N improvement, mass measurement accuracy was noticeably improved only at lower masses. The increased S/N did, however, yield a higher number of peaks and higher dynamic range throughout the entire segmented spectrum relative to the conventional broad-band spectrum. The additional assigned peaks include higher heteroatom species, as well as additional radicals and isotopologues. Segmenting can require a significant investment in data acquisition and analysis time over broad-band spectroscopy (∼1775% in this case) making it best suited for targeted analysis and/or when complete compositional coverage is important. Finally, the present segmented spectrum contains, to our knowledge, more assigned peaks than any spectrum of any kind (e.g., UV-vis, infrared, microwave, magnetic resonance, etc.).