小波变换漫反射红外光谱法测定剑麻果胶的酯化度

Determination of Degree of Esterification of Agave sisalana Pectin by Diffuse Reflectance Fourier Transform Infrared Spectroscopy with Wavelet Transform

采用小波变换,基于漫反射红外光谱(DR IFTS)技术建立了一种快速测定剑麻果胶酯化度(DE)的分析方法。小波变换作为信号处理工具可有效消除信号失真,信噪比(SNR)由84∶1增至96∶1,信号基线比(SBR)由7.7∶1升至8.3∶1,同时提高了果胶样品测定的精确度。以不同酯化度的果胶为标准,通过傅立叶变换红外光谱仪(FTIR)采用漫反射法建立DE与KM1740/(KM1740+KM1630)间的标准曲线,线性相关系数r=0.988。3种不同工艺提取的剑麻果胶ASP-w、ASP-h、ASP-u的酯化度分别为72.09%、62.98%和35.31%。F检验、t检验及配对t检验显示,DR IFTS法的测定结果与酸碱滴定法无显著差异。该方法具有样品用量少、操作简单、快速、灵敏度高等优点。

A rapid and sensitive method was developed for the determination of the degree of esterification（DE） of Agave sisalana pectin（ASP） by diffuse reflectance Fourier transform infrared spectrotroscopy（DRIFTS）. By processing the pectin spectrum obtained by DRIFTS with wavelet transform, the distortion of the original spectral signal caused by light scattering was effectively eliminated, for example, the signal-to-noise ratio（SNR） increased from 84 to 96, while the signal-to-baseline ratio （SBR） increased from 7.7 to 8.3. The precision （ expressed as RMSE） of the wavelet transform for ten replicates of ASP-h was 0. 011 62. The pectin spectra showed that the intensities of the absorption peak and peak area（KM） of the esterified group at 1 740 cm-1 and the carboxyl group at 1 630 cm-l were closely related with the DE. A linear relationship existed between DE and KM1740/（ KM174o ＋ KM1630 ） with a correlation coefficient of 0. 988. For three pectin samples extracted from Agave sisala- na with different＇technologies, the DE obtained for ASP-w, ASP-h and ASP-u by DRIFTS were 72.09% , 62.98% and 35.31% , respectively. The results of Student t-test indicated that no signif- icant difference existed between the results obtained by acid-base titration and DRIFTS methods.