Automated LC-HRMS(/MS) Approach for the Annotation of Fragment Ions Derived from Stable Isotope Labeling-Assisted Untargeted Metabolomics. Lehner, Bernhard Kluger, Christoph Bueschl, Karoline Sedelmaier, Marc Lemmens, Rudolf Krska, and Rainer Schuhmacher. Mass Isotopomer Analysis of Nucleosides Isolated from RNA and DNA Using GC/MS. Ines Miranda-Santos, Silvia Gramacho, Marta Pineiro, Karla Martinez-Gomez, Michel Fritz, Klaus Hollemeyer, Armindo Salvador, and Elmar Heinzle.Prediction Models of Retention Indices for Increased Confidence in Structural Elucidation during Complex Matrix Analysis: Application to Gas Chromatography Coupled with High-Resolution Mass Spectrometry. Eric Dossin, Elyette Martin, Pierrick Diana, Antonio Castellon, Aurelien Monge, Pavel Pospisil, Mark Bentley, and Philippe A.This article is cited by 19 publications. Finally, we implemented the FFC algorithm in an easy-to-use graphical user interface and made it publicly available at. In total, we report the chemical formulas and backbone carbon compositions for 160 fragment ions of 43 alkylsilyl-derivatives of primary metabolites. The FFC algorithm is able to integrate stable isotope labeling experiments into the analysis and can automatically exclude candidate formulas that do not fit the observed labeling patterns.1 We applied the FFC algorithm to create a fragment ion repository that contains the chemical formulas and retained carbon atoms of a wide range of trimethylsilyl and tert-butyldimethylsilyl derivatized compounds. The proposed algorithm is able to cope with general molecular rearrangement reactions occurring during EI in GC/MS measurements. Here, we present the fragment formula calculator (FFC) algorithm that can calculate chemical formulas for fragment ions where the chemical bonding (e.g., Lewis structures) of the intact molecule is known. For that reason, we developed an algorithm, based on a systematic bond cleavage, to determine chemical formulas and retained atoms for EI derived fragment ions. However, the process of mass spectral fragmentation is complex, and identifying the substructures and chemical formulas for these fragment ions is nontrivial. Fragment ions containing different carbon atoms are of special interest, since they can carry different flux information. For example, 13C-metabolic flux analyses ( 13C-MFA) are dependent on the exact knowledge of the number and position of retained carbon atoms of the unfragmented molecule. Moreover, the positional distribution of stable isotopes within a fragment ion is of high interest for stable isotope-assisted metabolomics techniques. Hence, the correct assignment of chemical formulas to fragment ions is of crucial importance for correct MIDs. The chemical formula of a fragment ion is usually applied to derive the correction matrix for accurate MID calculation. The analysis of fragment ions formed during EI, which contain only specific parts of the original molecule can provide valuable information on the positional distribution of the label. Most commonly, MIDs are derived from gas chromatography/electron ionization mass spectrometry (GC/EI-MS) measurements. The accurate determination of mass isotopomer distributions (MID) is of great significance for stable isotope-labeling experiments.

Ionic formula calculator