关键词: 木质素, 酚羟基, 羧酸基, 水相, 电位滴定

Abstract: The potentiometric titration in aqueous phase is used for determination content of phenolic hydroxyl and carboxyl on alkali lignin(AL) and sodium lignosulphonate(SL).The results show that the content of phenolic hydroxyl and carboxyl are 2.81 mmol·g^-1 and 1.72 mmol·g^-1 for AL,and 1.32 mmol·g^-1 and 0.86 mmol·g^-1 for SL,respectively.A comparison with classical non-aqueous potentiometric titration indicates that the stability is more excellent for the measurement in aqueous phase.The dynamic light scattering(DLS) method is used for the study of hydrodynamic diameter distributions of AL and SL in DMF and water solvents.The results show that they have stronger aggregation in DMF than in alkaline water,indicating that there is better dissolubility in alkaline aqueous solution than in DMF solvent.Therefore,it can be considered that the aqueous potentiometric titration is more suitable for the quantitative determination of phenolic hydroxyl and carboxyl contents on lignin-based compounds and can be an option for quantitative determination of the functional groups on lignin.

Key words: lignin, phenolic hydroxyl, carboxyl, aqueous phase, potentiometric titration