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. Author manuscript; available in PMC: 2018 Nov 28.
Published in final edited form as: Anal Chem. 2018 Jan 9;90(3):2001–2009. doi: 10.1021/acs.analchem.7b04089

Figure 2.

Figure 2.

Comparison of the absolute concentrations of 28 metabolites derived from NMR and NMR-guided MS for the same blood-serum sample (average CV = 4.1%). MS concentrations were derived on the basis of one of the serum samples that was used as the reference sample. Similar results were obtained irrespective of the serum sample that was used as the reference (see text). Glutamine and pyroglutamic acid were omitted because of errors arising from glutamine cyclization.15,25,26 Unless otherwise noted, the MS data were obtained using an AB Sciex QTrap 5500 mass spectrometer.