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.%引言木质素是自然界中仅次于纤维素的第二大可再生资源,是人类未来的主要资源来源[1].以木质素为原料制备新材料和化工原料,逐步替代化石等日趋枯竭的不可再生资源,正成为一种新的发展趋势.木质素主要是由苯丙烷单元(C6～C3)经碳碳键和醚键相互连接和无规则偶合而成的三维网状无定形高聚物[2],其分子结构中含有羟基(酚羟基和醇羟基)、双键、大π键、羧酸等基团[3],其中酚羟基和羧酸基能够在碱性溶液中电离,其含量决定了木质素在水溶液中的溶解性.由于有关木质素的化学改性反应基本都在水介质中进行,因此准确测定木质素的水溶性基团——酚羟基和羧酸基的含量对于木质素的化学改性和基础研究非常重要.
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