NaOH/尿素低温溶解法测定烟梗木质素含量的研究

摘要

A novel method to determine lignin content in tobacco leaf stems was developed. Leaf stems were extracted by NaOH/urea aqueous solution at low temperature to remove saccharides and other impurities. Acid treatment was carried out to break chemical bonds between lignin and cellulose/hemicellulose and obtain acid-soluble lignin under optimized conditions, i.e. 100℃ for 30min with sulfuric acid of 17.5 % and liquid-to-solid ratio of 80 mL·g-1. Residual was further treated by NaOH/urea aqueous solution to resolve high-molecular compound such as cellulose/hemicelluloses, and acid-insoluble lignin was thus obtained. Acid-soluble lignin was determined by UV absorbance at 325 nm,and acid-insoluble lignin was determined by combustion method. The RSD of lignin determination was below 3%. Organic solvent and concentrated sulfuric acid pretreatment was avoided, which improved the security of operations.%建立了一种准确测定烟梗木质素含量的新方法。用低温NaOH/尿素水溶液抽提烟梗，除去糖类等杂质，然后在优化条件（硫酸浓度17.5%、液固比80 mL·g-1、酸解温度100℃、酸解时间30 min）下采用酸处理打断烟梗中木质素与纤维素等组份之间的化学键，并得到酸溶木质素，残渣进一步用低温NaOH/尿素水溶液处理，溶解纤维素、半纤维素等天然高分子物质，得到酸不溶木质素。酸溶木质素采用分光光度法在325 nm处测定，酸不溶木质素采用灼烧法测定。本方法RSD小于3%，准确度良好，且减少了有机溶剂预处理和浓硫酸处理，提高了测试的安全性。