title: Performance evaluation of gas chromatography-atmospheric pressure chemical ionization-time-of-flight mass spectrometry for metabolic fingerprinting and profiling.
abstract: Gas chromatography-atmospheric-pressure chemical ionization-time-of-flight mass spectrometry (GC-APCI-TOFMS) was compared to GC × GC-electron ionization (EI)-TOFMS, GC-EI-TOFMS, GC-chemical ionization (CI)-quadrupole mass spectrometry (qMS), and GC-EI-qMS in terms of reproducibility, dynamic range, limit of detection, and quantification using a mix of 43 metabolites and 12 stable isotope-labeled standards. Lower limits of quantification for GC-APCI-TOFMS ranged between 0.06 and 7.81 μM, and relative standard deviations for calibration replicates were between 0.4% and 8.7%. For all compounds and techniques, except in four cases, R(2) values were above 0.99. Regarding limits of quantification, GC-APCI-TOFMS was inferior to only GC × GC-EI-TOFMS, but outperformed all other techniques tested. GC-APCI-TOFMS was further applied to the metabolic fingerprinting of two Escherichia coli strains. Of 45 features that differed significantly (false discovery rate < 0.05) between the strains, 25 metabolites were identified through highly accurate and reproducible (Δm ± SD below 5 mDa over m/z 190-722) mass measurements. Starting from the quasimolecular ion, six additional metabolites were identified that had not been found in a previous study using GC × GC-EI-TOFMS and an EI mass spectral library for identification purposes. Silylation adducts formed in the APCI source assisted the identification of unknown compounds, as their formation is structure-dependent and is not observed for compounds lacking a carboxylic group.
authors.affiliation: Institute of Functional Genomics, University of Regensburg, Josef-Engert-Straße 9, 93053 Regensburg, Germany.
authors.forename: Christian J
authors.initials: CJ
authors.lastname: Wachsmuth
authors.forename: Martin F
authors.initials: MF
authors.lastname: Almstetter
authors.forename: Magdalena C
authors.initials: MC
authors.lastname: Waldhier
authors.forename: Michael A
authors.initials: MA
authors.lastname: Gruber
authors.forename: Nadine
authors.initials: N
authors.lastname: Nürnberger
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Oefner
authors.forename: Katja
authors.initials: K
authors.lastname: Dettmer
mesh_terms: D001274:Atmospheric Pressure; D002849:Chromatography, Gas; D004926:Escherichia coli / Q000737:chemistry* / Q000378:metabolism; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization