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【讨论】环糊精相溶解度法测定包合比和包合常数 已有4人参与
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最近看到1篇文献是用相溶解度法测定包合比和包合常数的，我们常用的是AL型的，也就是包合比是1:1的，这篇文献可以用相溶解度法测定包合比和分别确定1:1和1:2的稳定常数，但是文献中的方法我还是没有看懂： 相溶解度图如下：   方法为 methods： 2.1. PHASE SOLUBILITY STUDIES The solubility studies were carried out according to the method reported by Higuchi and Connors [3]. Excess of 2,4-D (50 and 20 mg for the - and -CD assays, respectively) were accurately weighed into 50 mL Erlenmeyer flasks, adding 10 mL of unbuffered water containing increasing concentrations of -CD (0.01–0.1 M range) and -CD (0.002–0.030 M range). In the -CD system, with the purpose of making the curve asymptotic, it was necessary to add an excess of -CD much greater than the solubility limit (0.016 M). These flasks were sealed and shaken at 25 C for one week. After equilibrium, the samples were filtered with a syringe through a 0.22 mMillipore cellulose nitrate membrane filter, properly diluted and analysed spectrophotometrically at 284 nm (Hitachi U-2000). results： 3.1. PHASE SOLUBILITY STUDIES The phase solubility diagrams obtained for 2,4-D with 1- and 2-CD are shown in Figure 1. According to Higuchi and Connors, both diagrams can be classified as BS type. An insoluble microcrystalline complex was formed from the solution at 0.020 M for the 1-CD system and 0.009 M for the 2-CD one. Therefore, the 2,4-D content of the precipitated complex (Sc) is equal to the difference between the total amount of 2,4-D added to the system (ST) and the pesticide in solution when the plateau region is reached (SM). The CD content in the complex (Lc), corresponds to the CD concentration during the plateau region. So, the precipitated complex stoichiometry could be expressed as follows: R D Sc=Lc: (1) Table I reports the different calculated values from the solubility assay for both systems. The precipitates have the stoichiometries SL2 for the 1-CD complex (two 1- CD molecules are involved for the inclusion of one 2,4-D molecule) and SL for the 2-CD complex. 其中1-CD代表阿尔法环糊精，2-CD代表贝塔环糊精，因为是从文献直接粘过来的所以这里不识别。我就是看不明白表里面（Table1）的ST是怎么得到的，如果是原来的20mg和50mg也不对啊，换算出来的浓度也对不上，请大家帮我看看这个包合比是怎么算出来的呢？ 文献出处：Journal of Inclusion Phenomena and Macrocyclic Chemistry 37: 171–178, 2000. |
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2楼2010-10-28 13:03:49
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