Evaluation of Hydrophobicity for Fatty Acids Using Reversed-phase Thin Layer Chromatography

Hydrophobicity of ingredients is important for designing food, pharmaceuticals, and cosmetics. Here, we evaluated the hydrophobicity of fatty acids and showed the effect of the alkyl length and the unsaturation degree using reversed-phase thin layer chromatography (RP-TLC). A linear relation was obtained between the methanol concentration in a mobile phase and the R_m value. The linear regression analysis was achieved and the hydrophobicity value R_mw was obtained using the robust regression (MM-estimator). The hydrophobicity of fatty acids depends on the structure of alkyl chain as follows: a longer alkyl chain in fatty acid increased the hydrophobicity. Additionally, the hydrophobicity increased as the number of unsaturated parts increased. Fatty acid with branched structures were less hydrophobic than that with straight chained structures.