Fig 1. Analytical characterization of derivatized SCFA standards.

(A) Reaction scheme for the aniline derivatization of SCFAs. (B) Overlaid extracted ion chromatograms (EIC) corresponding to a ¹²C-and ¹³C-derivatized SCFA mix standard solution detected in selected reaction monitoring mode. Red HPLC traces correspond to the ¹³C-labeled analytes. (Inset) A single reporter MS/MS fragment was used for analyzing all SCFA: m/z [M+H]⁺ → 94.1. (C) Relative MS signal intensities of a derivatized mixed solution of ¹²C- and ¹³C- SCFA analytes at a concentration of 10 μM and 5 μM, respectively. Data were acquired in full scan mode. EDC, N-(3-Dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride; CE, collision energy in eV.