Heinemann Matthias, Meinberg Holger, Büchs Jochen, Koss Hans-Jürgen, Ansorge-Schumacher Marion B
RWTH Aachen University, Biochemical Engineering, 52056 Aachen, Germany.
Appl Spectrosc. 2005 Mar;59(3):280-5. doi: 10.1366/0003702053585363.
A new method based on Raman spectroscopy is presented for non-invasive, quantitative determination of the spatial polymer distribution in alginate beads of approximately 4 mm diameter. With the experimental setup, a two-dimensional image is created along a thin measuring line through the bead comprising one spatial and one spectral dimension. For quantitative analysis of the Raman spectra, the method of indirect hard modeling was applied to make use of the information contained in the entire recorded spectra. For quantification of the alginate signals from within the beads, a calibration curve acquired from sodium alginate solutions was used after it was shown that only negligible differences occur between signals from alginate solutions and alginate gels. The distribution of alginate over the bead gel matrix was acquired with high spatial (51 microm) and time (12 s) resolution. The inhomogeneous distribution obtained using the new measuring technique is qualitatively in excellent agreement with data from the literature. In contrast to known measuring techniques, correct quantitative information about the spatial polymer distribution within the matrix was derived. It gave an alginate mass fraction of approximately 0.045 g/g at the edges and 0.02 g/g in the center of the beads. Next to the determination of mere polymer concentrations, the excellent time resolution of the presented method will enable investigation of the dynamic process of gel formation and it will also serve as a basis for investigation of mass transfer of small diffusing molecules in alginate matrices.
本文提出了一种基于拉曼光谱的新方法，用于对直径约4毫米的藻酸盐微珠中的聚合物空间分布进行非侵入式定量测定。利用该实验装置，沿着穿过微珠的一条细测量线创建二维图像，该图像包含一个空间维度和一个光谱维度。为了对拉曼光谱进行定量分析，应用间接硬建模方法来利用整个记录光谱中包含的信息。为了对微珠内的藻酸盐信号进行定量，在表明藻酸盐溶液和藻酸盐凝胶的信号之间仅存在可忽略不计的差异之后，使用从海藻酸钠溶液获得的校准曲线。以高空间分辨率（51微米）和时间分辨率（12秒）获取了藻酸盐在微珠凝胶基质上的分布。使用新测量技术获得的不均匀分布在定性上与文献数据非常吻合。与已知测量技术相比，得出了关于基质内聚合物空间分布的正确定量信息。在微珠边缘处得到的藻酸盐质量分数约为0.045克/克，在微珠中心处为0.02克/克。除了测定聚合物浓度外，所提出方法的出色时间分辨率将能够研究凝胶形成的动态过程，并且还将作为研究小扩散分子在藻酸盐基质中传质的基础。
