Short chain fatty acids (SCFA's) play an important role in diagnosing gastrointestinal abnormalities. Due to complexities of biological matrices, current methods require several tedious steps for SCFA measurement by gas chromatography (GC) analysis. We propose aqueous extraction (AE) may minimize extraction processing and increase sensitivity when using GC with flame ionization detection (FID) to detect nine SCFAs: acetic, propionic, iso-butyric, butyric, iso-valeric, valeric, 4-methyl valeric, hexanoic and heptanoic acids. Fecal samples were suspended in bicarbonate buffer, vortexed, centrifuged and acidified with a 1.0 M HCl solution then filtered through a 0.45 µm syringe filter directly into a GC vial (AE). AE samples were further extracted via liquid-liquid extraction with tert-butyl methyl ether (TBME) and separated into a GC vial (liquid-liquid extraction, LLE). Both methods (AE and AE + LLE) produced excellent linearity with correlation coefficients ranging from 0.997-0.99999. However, AE improved sensitivity 13-24-fold compared to AE + LLE as measured by signal-to-noise ratios. The use of AE also reduces analysis time and associated errors of sample preparation. The proposed method has been optimized for SCFA analysis in human fecal samples but can likely be applied to a variety of biological matrices. The method is being validated for precision and recovery.

Improved GC method for the determination of short chain fatty acids in human fecal samples

ACS Spring 2022

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