NaOH/尿素低温溶解法测定烟梗木质素含量的研究

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，采用优化的酸处理条件（硫酸浓度17.5 %、液固比80 mL?g-1、酸解温度100 ℃、酸解时间30 min）打断烟梗中木质素与纤维素等组份之间的化学键，残渣用低温NaOH/尿素水溶液进一步溶解纤维素、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。 

Study on NaOH/urea dissolving method for determining lignin content in the tobacco stems in low temperature

A novel method to determine the lignin content in the tobacco stems was developed in this paper. The method to determine acid-insoluble lignin is based on the NaOH/urea aqueous solution’s strong ability to dissolve natural polymer at low temperature, such as cellulose, hemicellulose, etc., followed by breaking the bonds between lignin and cellulose/hemicellulose with dilute acid treatment. The optimum conditions for acid treatment was carried out at 100℃ for 30 min with sulfuric acid of 17.5% and liquid-to-solid of 80mL/g. UV absorbance in 325nm was selected to quantify the content of acid-soluble lignin, aiming at avoiding the interference of protein, etc. The content of sugar in acid-insoluble lignin is less 2% and the relative standard deviation for lignin determination is below 2%, which indicate that this method is provided with good accuracy and precision. Moreover, it reduces the organic solvent and concentrated sulfuric acid pretreatment and improves the security of the test.