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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 4.

Figure 4.

Comparison of absolute concentrations for four metabolites derived from NMR-guided MS and targeted MS using 13C,15N-isotope-labeled (uniformly) internal standards. Here, the NMR-guided-MS concentration for each metabolite was determined separately using each of the eight serum samples as references, and slight variation in concentration values due to different references is shown with an error bar. The median CV between the values from the NMR-guided-MS method and isotope-labeled-internal-standard MS was 6.2%.