Comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC x GC-TOF) for high resolution metabolomics: biomarker discovery on spleen tissue extracts of obese NZO compared to lean C57BL/6 mice

Comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC x GC-TOF) was applied for the analysis of complex metabolite profiles from mouse spleen. The resulting two-dimensional chromatograms proved that mass spectral quality and sensitivity were largely improved by the enhanced resolution and zone compression, which are features of GC x GC operation, when compared to classical one-dimensional GC-TOF methods. The improved peak capacity of GC x GC allowed for peaks to be detected that could previously not be separated in one-dimensional GC. A measure of the combined power of chromatographic and mass spectral deconvolution resolution is called "analytical purity", with higher values indicating less pure peaks. GC x GC-TOF lead to the detection of 1200 compounds with purity better than 0.2, compared to 500 compounds with purity up to 2.5 in one-dimensional GC-TOF. The compounds identified include many of the compounds previously reported in NMR studies and other methods on mammalian tissues. Spleen samples of several obese NZO mice and lean C57BL/6 control strains were analyzed in order to demonstrate the applicability of GC x GC-TOF for biomarker identification.