Development of a simple, low-cost and rapid thin-layer chromatography method for the determination of individual volatile fatty acids

Abstract

In this paper, a new thin-layer chromatography (TLC) method for the determination of individual volatile fatty acids (VFAs) is presented. The experimental procedure is based on the derivatization of VFAs with activating agents and a naphthalene-based amine to form an amide derivative, followed by fast TLC separation of these VFA derivatives and visualization with phosphomolybdic acid at room temperature. Quantification is then performed by densitometric measurements using free software after taking TLC pictures in a home-made black box for homogeneous and reproducible lighting of the plates. Optimization of the experimental conditions enables fast determination (20 minutes for 3 samples) of VFAs with detection limits (1.5–2.5 mg L⁻¹) and relative standard deviations (4.6–6.7%) satisfactory enough for our analytical purpose using low-cost instruments with easy to find materials and software. The protocol was then applied to real samples (aqueous extracts of sewage sludge composts) and the results were compared with gas chromatography analysis with good agreement between the two methods.