偏最小二乘辅助紫外可见光谱法同时测定烟草中的葡萄糖与木糖含量

Simultaneous Detection of Glucose and Xylose in Tobacco by Using Partial Least Squares Assisted UV-Vis Spectroscopy

烟草中含有葡萄糖、果糖、麦芽糖、蔗糖、木糖等多种糖类物质,占据烟草干重的25%~50%,是烟草的重要组成部分,也是评估烟草内在品质的重要指标。不同的糖类物质在卷烟燃烧过程中会生成不同产物,从而直接或间接地影响卷烟的香气和口感。建立烟草中各种单糖的测定方法,对烟草制品的质量控制具有现实意义。传统的检测方法如费林试剂法、连续流动分析法只能对烟草中的水溶性糖或总糖含量进行测定,无法对单一糖组分进行定量检测;气相色谱、液相色谱等方法虽能检测出不同单项,但是存在样品前处理过程麻烦、检测耗时较长等局限性。该工作在传统间苯三酚显色法测定木糖的基础上,以显色机理对该方法进行改进,解决了该检测体系下葡萄糖显色效果不佳的技术问题,可通过紫外可见光谱技术简单、高效地实现对烟草及卷烟制品中葡萄糖和木糖含量的精准测定。当同时测定上述两种糖组分时,由于二者的紫外可见光谱出峰位置相近,会相互影响彼此的测量准确性。为消除这一干扰,采用偏最小二乘回归法(PLS)建立光谱分析的多元校正模型,辅助改进后的间苯三酚法对烟草及其制品中葡萄糖和木糖含量进行同时检测。研究结果表明:改进后的间苯三酚法对于葡萄糖和木糖的单糖溶液,浓度分别在0.05~0.4和0.10~0.80 mmol·L^(-1)范围内时线性关系良好,该方法的检出限和定量限分别为0.001 7、 0.005 7 mmol·L^(-1)和0.007 2、 0.024 mmol·L^(-1),批内变异系数的范围为0.69%~3.03%,加标回收率范围为96.72%~102.85%,提取液中木素含量对测定结果没有显著干扰。对于葡萄糖和木糖组成的混糖溶液,采用外部检验对模型效果进行评价,外部检验集的预测值与理论值的相关系数R^(2)=0.994 7,相对偏差小于10%。该方法能够快速准确的测定烟草及烟草制品中葡萄糖和木糖含量,为烟草行业提供一种有效的单糖分析方法。

Tobacco contains a variety of sugars,including glucose,fructose,maltose,sucrose,xylose,etc.These sugars account for 25%to 50%of the dry weight of tobacco and are an important component and a crucial criterion for measuring the intrinsic quality of tobacco.Different sugars produce different products during the combustion process of cigarettes,which directly or indirectly affect the aroma and taste of cigarettes.Therefore,establishing methods for determining various monosaccharides in tobacco is relevant for the quality control of tobacco products.Traditional detection methods such as Ferring's reagent method and continuous flow analysis can only determine the content of water-soluble sugars or total sugars in tobacco,and cannot quantify single sugar components.However,gas chromatography and liquid chromatography can detect different monosaccharides,they have limitations such as troublesome sample pre-treatment process and long detection time.In this work,based on the traditional phloroglucinol chromogenic method for determination of xylose,the method was improved based on the color development mechanism to solve the technical problem of poor color development of glucose under this detection system,and the precise determination of glucose and xylose content in tobacco and cigarette products can be achieved and efficiently by UV-visible spectroscopy.When the above two sugar fractions are measured simultaneously,the UV spectra can affect each other's measurement accuracy due to their similar peak positions.A multivariate correction model for spectral analysis was developed using partial least squares regression(PLS),aided by a modified phloroglucinol chromogenic method to simultaneously determine glucose and xylose contents in tobacco and its products.The results showed that the linearity of the modified phloroglucinol method was satisfactory for glucose and xylose solution at concentrations in the range of 0.05~0.4 and 0.10~0.80 mmol·L^(-1),respectively,and the limits of detection and limits of quantification of the method were 0.0017,0.0057 mmol·L^(-1)and 0.0072,0.024 mmol·L^(-1),respectively.The intra-batch coefficients of variation were in the range of 0.69%~3.03%,and the spiked recoveries were in the range of 96.72%~102.85%.The lignin content in the extracts did not interfere significantly with the determination results.For the mixed sugar solution composed of glucose and xylose,the external test was used to evaluate the model effect,and the correlation coefficient R^(2)=0.9947 between the predicted and theoretical values of the external test set was within 10%relative deviation.It can be seen that this method can quickly and accurately determine the content of glucose and xylose in tobacco and tobacco products and provide an effective method for monosaccharide analysis in the tobacco industry.