CAPILLARY-ELECTROPHORESIS STUDIES OF PECTINS

Capillary electrophoresis (CE) has been used to study a variety of pec tins that originate from different sources (citrus, apple and beet) an d have different anhydrogalacturonic acid (AGU) contents (86.2-63.2%). This CE method can be used for the quantitative detection of aqueous solutions of pectins in the concentration range 0.5-5 mg mL(-1) using a 50 mM pH 7.0 phosphate background electrolyte and UV detection at 19 2 nm. Using lemon pectin calibration standards in the degree of esteri fication (DE) range 31.1-75.8%, the technique was used to determine th e DE of a further 11 pectin samples. Results are shown to be in excell ent agreement with those obtained by titration, irrespective of the pe ctin type and neutral sugar content. The method also allows determinat ion of the intermolecular DE distribution (variation in DE between mol ecules), from the CE peak shape. Results for the DE distribution are c ompared with those obtained by ion-exchange chromatography in combinat ion with size-exclusion chromatography (IEC-SEC). Both DE and DE distr ibution are obtained from CE in approximately 2 h, inclusive of sample preparation and calibration, in contrast to 2 days for the IEC-SEC me thod. (C) 1998 Elsevier Science Ltd. All rights reserved.