氢氧化钠/尿素法和硫酸法测定烟草木质素的对比分析

摘要

In order to compare the difference of NaOH/Urea (NU) method and sulfuric acid method in determining the lignin content in tobacco, the lignin content in the tobacco stems and leaves sampled from Guangdong, Sichuan, Hunan, Yunnan and Guizhou were determined by both methods, and the removal rate of interfering substances in pretreatment process and the changes of content and structure of lignin in acid hydrolysis process were compared. The results showed that: 1)The pretreatment of NU method was more efficient in removal of interfering substances. 2) Diluted sulfuric acid solution was applied for hydrolysis in NU method, it reduced the degradation of lignin in tobacco. Moreover, the UV absorbance at 325 nm was selected for the quantification of acid soluble lignin (ASL), it avoided the interference of protein and furfural and improved the accuracy and reproducibility of the determination result. 3)The acid insoluble lignin isolated by NU method featured lower oxidation degree and less structural change, hence better represented the true structural characteristics of lignin in tobacco. NU method is more suitable for determining the lignin content in tobacco than is sulfuric acid method.%为了对比氢氧化钠/尿素法（NU法）和硫酸法在测定烟草中木质素含量（质量分数，下同）的差异性，采用NU法和硫酸法测定广东、四川、湖南、云南和贵州5个产区烟梗和烟叶的木质素含量，分析了两种方法在预处理过程的干扰物质去除率及酸解过程木质素含量和结构变化。结果表明：①与硫酸法相比，NU法预处理对干扰物质的去除率更高。②NU法采用稀酸酸解，减少了烟草中木质素的降解；选择在325 nm处测定酸溶木质素（ASL）的紫外吸光度，避免了蛋白质和糠醛对ASL的干扰，提高了烟草木质素测定结果的准确度和重现性。③与硫酸法相比，NU法分离得到的酸不溶木质素（AIL）的氧化程度低、结构变化小，因而更能反映烟草木质素的结构特征。NU法比硫酸法更加适用于烟草木质素的含量测定。