Abstract:

A method to measure the contents of soluble lignin and furfural in the lingocellulosic pre-hydrolysis liquid was developed based on UV spectroscopy in the present work. The UV spectrograms of the low molecular organic acids, furfural and the pre-hydrolysis liquid were discussed. Formic acid and acetic acid had significant absorption at 205 nm, and furfural had absorption maxima close to 280 nm. The traditional methods for quantification of lignin based on lignin characteristic peak location of 205 nm and 280 nm was not suitable for the determination of soluble lignin in the pre-hydrolysis liquid. The study presented elimination of the interference of furanic compounds by reduction with alkaline sodium borohydride. The results showed that sodium borohydride significantly decreased absorbance close to 280 nm, and the higher the pre-hydrolysis conditions, the more decreased the absorbance after reduction, indicating high level of furfural. With lignin extracted from Acacia wood and reeds as standard sample, the relationship between absorbance at 280 nm and concentration of lignin was linear and pertinent coefficient reached 0.999, which met the needs of quantitative determination. The difference of absorbance between the samples before and after full reduction could be used for quantification of furfural. The pertinent coefficient of absorbance at 280 nm and concentration of furfural reached 0.998. The results of reproductive experiment showed that recovery was 98.14%—99.88% and relative standard deviation was 0.17%-0.35%.

Key words: UV spectral, biomass, hydrolysis, lignin, degradation, furfural

摘要：

采用紫外光谱探讨了低分子有机酸、糠醛和木质纤维高温预水解液(PHL)的紫外吸收谱图特征。甲酸和乙酸在近205 nm处有显著吸收, 而糠醛在近280 nm处有显著吸收, 以205 nm或280 nm为木素特征吸收位置的传统木素测定方法不适于高温预水解液的溶解性木素测定。研究提出碱性硼氢化钠还原处理预水解液, 消除糠醛的紫外吸收, 进而定量测定溶解性木素含量的方法。结果表明, 硼氢化钠可显著降低近280 nm处吸收值, 预水解条件越高, 还原前后吸收差值降低越多, 说明糠醛类物质含量高。以提取相思木和芦苇木素为标样, 280 nm处吸光度与浓度线性相关系数均达到0.999, 满足定量测定的需要。充分还原前后280 nm吸收差值可用于糠醛的定量, 糠醛标样280 nm处吸光度与浓度线性相关性为0.998, 糠醛测定回收率为98.14%~99.88%, 相对标准偏差为0.17%~0.35%。

关键词: 紫外光谱, 生物质, 水解, 木素, 降解, 糠醛