N-octadecylpectinamide, a hydrophobic sorbent based on modification of highly methoxylated citrus pectin

N-octadecylpectinamides with degrees of substitution (DA) of 5–32% were prepared by heterogeneous amino-de-alkoxylation of HM citrus pectin (DM=73%) with n-octadecylamine. FT-Raman, FT-IR, FT-NIR and 13C CP/MAS NMR spectroscopic studies indicated both secondary amide and n-octadecyl groups in the modified pectin samples. Comparing laser diffraction, image analysis and electronic microscopy of the initial HM citrus pectin and the final product of aminolysis confirmed that the size distribution and the shape of solid pectin particles significantly changed on substitution. The sorption properties of the water-insoluble modified pectin (DA=32%) were tested by reverse phase (RP) chromatography using this product as the stationary phase. According to RP chromatography, N-octadecylpectinamide is able to absorb selectively non-polar molecules and polar molecules with non-polar parts. However, it still has some residual hydrophilicity due to the presence of polar groups in the pectin framework.