Quantitative data on the speciation of chitosan (310 kDa) with low and high molecular weight carboxylates in aqueous solution are reported. The following carboxylic ligands were considered: monocarboxylate (butyrate); dicarboxylates (malonate, succinate, azelate); tricarboxylate (1,2,3-propanetricarboxylate); tetracarboxylate (1,2,3,4-butanetetracarboxylate); polyacrylates (2.0 and 20 kDa); polymethacrylate (5.4 kDa). The investigation was performed by potentiometry at t ¼ 25C, at low ionic strength (without addition of supporting electrolyte) and at I ¼ 0:15mol L1 (NaCl). For all the systems the formation of (chitosan)LHi species was found (L¼carboxylic ligand; i¼1 to 4 depending on the carboxylic ligand considered). The stability of proton– chitosan–carboxylate species depends on the number of carboxylic groups involved in the complexation, and it was possible to calculate a rough free energy value per bond DGn ¼152kJ mol1. By using the stability data, the quantitative sequestering capacity of chitosan towards the carboxylates here considered [expressed as the– log(total chitosan concentration) necessary to bind 50% of carboxylate, i.e., pL50] was calculated for different pH values, at low ionic strength and at I ¼ 0:15 mol L1. The pL50 values, ranging from 3 to 7, show that chitosan is quite a strong sequestering agent towards carboxylates. Evidences were also obtained for the different behaviour between low and high molecular weight carboxylates.

Speciation of Chitosan with low-and high-molecular -weight carboxylates in aqueous solution

DE STEFANO, Concetta;SAMMARTANO, Silvio
2009-01-01

Abstract

Quantitative data on the speciation of chitosan (310 kDa) with low and high molecular weight carboxylates in aqueous solution are reported. The following carboxylic ligands were considered: monocarboxylate (butyrate); dicarboxylates (malonate, succinate, azelate); tricarboxylate (1,2,3-propanetricarboxylate); tetracarboxylate (1,2,3,4-butanetetracarboxylate); polyacrylates (2.0 and 20 kDa); polymethacrylate (5.4 kDa). The investigation was performed by potentiometry at t ¼ 25C, at low ionic strength (without addition of supporting electrolyte) and at I ¼ 0:15mol L1 (NaCl). For all the systems the formation of (chitosan)LHi species was found (L¼carboxylic ligand; i¼1 to 4 depending on the carboxylic ligand considered). The stability of proton– chitosan–carboxylate species depends on the number of carboxylic groups involved in the complexation, and it was possible to calculate a rough free energy value per bond DGn ¼152kJ mol1. By using the stability data, the quantitative sequestering capacity of chitosan towards the carboxylates here considered [expressed as the– log(total chitosan concentration) necessary to bind 50% of carboxylate, i.e., pL50] was calculated for different pH values, at low ionic strength and at I ¼ 0:15 mol L1. The pL50 values, ranging from 3 to 7, show that chitosan is quite a strong sequestering agent towards carboxylates. Evidences were also obtained for the different behaviour between low and high molecular weight carboxylates.
2009
File in questo prodotto:
Non ci sono file associati a questo prodotto.
Pubblicazioni consigliate

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11570/1894752
 Attenzione

Attenzione! I dati visualizzati non sono stati sottoposti a validazione da parte dell'ateneo

Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 8
  • ???jsp.display-item.citation.isi??? 7
social impact