Fig. 1.

Development of the SCFA extraction protocol for fecal and plasma samples. (A) Overlaid GC-MS chromatograms of SCFAs in the standard solution, pooled fecal samples, and pooled plasma samples. (B) The mass spectrum showing the quantifier mass and qualifier mass. (C) Overview of SCFA extraction and analysis procedure. (D) Recoveries from SCFA extraction optimization (* denotes the final optimized conditions that were used to extract fecal SCFAs and plasma SCFAs). Abbreviations: DE, an extraction protocol that used diethyl ether solvent; FC, an extraction protocol using pooled fecal samples; PM, an extraction protocol using plasma sample; FC9r and PM3r, repeated conditions of FC9 and PM3, respectively. The different conditions are indicated in more detail in Supplementary table S2.