Jiangsu Province Biomass Energy and Materials Laboratory , Institute of Chemical Industry of Forest Products, CAF , Nanjing 210042 , China.
J Agric Food Chem. 2018 Oct 24;66(42):11000-11007. doi: 10.1021/acs.jafc.8b03653. Epub 2018 Oct 16.
Complex formation and precipitation of germanium by a well-characterized hydrolyzable tannin, 1,2,3,4,6-penta- O-galloyl-β-d-glucose (PGG), was studied in this work. Two simple phenolic compounds, methyl gallate and gallic acid, were also used for comparison purposes. The influence of pH on the stoichiometry and conditional association constants (log K) of the germanium complexes was investigated. UV-visible spectroscopy showed the successive formation of GePGG and GePGG at pH 6.0 and of GePGG at pH 4.0. The results of the precipitation experiments indicated that germanium precipitation was influenced by organic solvents, pH values, the germanium/PGG ratio, and the presence of zinc. Acetone had the biggest effect on the solubility of these complexes, and lower pH values favored the precipitation of the complex. The results showed that a germanium/PGG ratio of more than 3:1 was essential for precipitation. Furthermore, the presence of zinc ions in the solution decreased the precipitation.
在这项工作中，研究了一种具有良好水解性能的单宁酸（1,2,3,4,6-五-O-没食子酰基-β-d-葡萄糖（PGG））与锗形成配合物和沉淀的情况。同时，还使用了两种简单的酚类化合物（没食子酸甲酯和没食子酸）进行比较。考察了 pH 值对锗配合物的化学计量比和条件缔合常数（log K）的影响。紫外-可见光谱显示，在 pH 6.0 下形成了 GePGG 和 GePGG，在 pH 4.0 下形成了 GePGG。沉淀实验的结果表明，锗的沉淀受有机溶剂、pH 值、锗/PGG 比以及锌的存在的影响。丙酮对这些配合物的溶解度影响最大，较低的 pH 值有利于配合物的沉淀。结果表明，沉淀的必要条件是锗/PGG 比大于 3:1。此外，溶液中锌离子的存在会降低沉淀的形成。
