title: Characterisation of Ca- and Al-pectate gels by thermal analysis and FT-IR spectroscopy.
abstract: Thermal analysis (TG-DTA) and FT-IR spectroscopy have been performed on calcium-pectate membranes to investigate their structure and the consequent variation caused by aluminium sorption. Calcium-polygalacturonate (Ca-PG) membranes, model systems of the soil-root interface, were exposed to aluminium solutions at different concentrations (25-800 microM). Three different pHs (3.50, 4.00 and 4.50) were chosen to study the influence of different aluminium species, such as [Al(H2O)6]3+, [Al(OH)(H2O)5]2+ and [Al(OH)2(H2O)(4)]+, on the structure of the Ca-PG membrane. The DTA profiles and FT-IR spectra showed how aluminium sorption induces structural modifications leading to a reorganisation of the chain aggregates and a weakening of the structure. Higher pH, that is, 4.00 and 4.50, and thus hydrolytic aluminium species and related higher calcium content maintain a more regular structure than at pH 3.50. At pH 3.50, both the effect of [Al(H2O)6]3+ and a major calcium release had a greater impact and thus induced a greater weakening of the structure.
authors.affiliation: Department of Agroenvironmental Sciences and Technologies-Alma Mater Studiorum, University of Bologna, Viale Fanin 40, 40127 Bologna, Italy. tmimmo@agrsci.unibo.it
authors.forename: Tanja
authors.initials: T
authors.lastname: Mimmo
authors.forename: Claudio
authors.initials: C
authors.lastname: Marzadori
authors.forename: Daniela
authors.initials: D
authors.lastname: Montecchio
authors.forename: Carlo
authors.initials: C
authors.lastname: Gessa
mesh_terms: D000535:Aluminum / Q000737:chemistry* / Q000494:pharmacology; D002152:Calorimetry, Differential Scanning; D006863:Hydrogen-Ion Concentration; D008567:Membranes, Artificial; D010368:Pectins / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D008567:Membranes, Artificial; D010368:Pectins; D000535:Aluminum; C003181:polygalacturonic acid