¹³C CP/MAS NMR Spectroscopy in the Analysis of Pectins

Abstract

¹³C CP/MAS NMR spectra of powder commercial pectins were recorded and interpreted. NMR spectral results were applied for the calculation of galacturonic acid content (GalA), degrees of methylation (DM) and acetylation (DA). In most cases NMR values from GalA and DM agreed with values obtained by conventional methods (photometry and HPLC). The determination of DA using NMR data was successful only in the case of sugar beet pectin with high acetyl content. The C-6 carbon region was studied in detail and the chemical shift and the shape of peaks in this region were strongly influenced by the ratio of uronic carboxyl forms. Correlation between C-6 carbon chemical shift and DM values for pectins in their protonated form was evaluated.