title: Producing absorption mode Fourier transform ion cyclotron resonance mass spectra with non-quadratic phase correction functions.
abstract: BACKGROUND
  Previously described methods for producing absorption mode Fourier transform ion cyclotron resonance (FTICR) mass spectra have all relied on the phase correction function being quadratic. This assumption has been found to be invalid for some instruments and spectra and so it has not been possible to produce absorption mode spectra for these cases.
  
  
  METHODS
  The Autophaser algorithm has been adapted to allow nth order polynomial phase correction functions to be optimized. The data was collected on a modified Thermo LTQ FTICR mass spectrometer, using electrospray ionization and a novel ICR cell design (NADEL). Peak assignment and mass calibration were undertaken using the pyFTMS framework.
  
  
  RESULTS
  An nth-order phase correction function has been used to produce an absorption mode mass spectrum of the maltene fraction of a crude oil sample which was not possible using the previous assumption that the phase correction function must be quadratic. Data processing for this spectrum in absorption mode has shown the expected benefits in terms of increasing the number of assigned peaks and also improving the mass accuracy (i.e. confidence) of the assignments.
  
  
  CONCLUSIONS
  It is possible to phase-correct time-domain data in FTICRMS to yield absorption mode mass spectra representation even when the data does not correspond to the theoretical quadratic phase correction function predicted by previous studies. This will allow a larger proportion of spectra to be processed in absorption mode.
authors.affiliation: Department of Pharmaceutical Sciences, School of Pharmacy, University of Maryland Baltimore, MD, USA.
authors.forename: David P A
authors.initials: DP
authors.lastname: Kilgour
authors.affiliation: Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, 1015, Lausanne, Switzerland.
authors.forename: Konstantin O
authors.initials: KO
authors.lastname: Nagornov
authors.affiliation: Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, 1015, Lausanne, Switzerland.
authors.forename: Anton N
authors.initials: AN
authors.lastname: Kozhinov
authors.affiliation: Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, 1015, Lausanne, Switzerland.
authors.forename: Konstantin O
authors.initials: KO
authors.lastname: Zhurov
authors.affiliation: Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne, 1015, Lausanne, Switzerland.|Spectroswiss Sàrl, EPFL Innovation Park, 1015, Lausanne, Switzerland.
authors.forename: Yury O
authors.initials: YO
authors.lastname: Tsybin
mesh_terms: D017357:Cyclotrons; D005583:Fourier Analysis; D013058:Mass Spectrometry / Q000295:instrumentation* / Q000379:methods; D010578:Petroleum / Q000032:analysis*
chemical_list: D010578:Petroleum