Takeda Yasuyuki, Yasui Aiko, Morita Megumi, Katsuta Shoichi
Department of Chemistry, Faculty of Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan.
Talanta. 2002 Mar 4;56(3):505-13. doi: 10.1016/s0039-9140(01)00581-1.
To investigate quantitatively the anion effect on the extraction-ability and -selectivity of benzo-18-crown-6 (B18C6) for alkali metal ions, the constants for overall extraction into various diluents having low dielectric constants (K(ex)) and aqueous ion-pair formation (K(MLA)) of B18C6-sodium and potassium perchlorate 1:1:1 complexes (MLA) were determined at 25 degrees C. The K(ex) value was analyzed by the four fundamental equilibrium constants. The K(MLA) values were determined by applying our established method to this perchlorate extraction system. The K(M(B18C6)A) value of the perchlorate is much larger for K(+) than for Na(+), and is much smaller than that of the picrate. The K(M(B18C6)A) value makes a minor contribution to the magnitude of K(ex) for the perchlorate system, but a major contribution to that for the picrate one. The distribution behavior of the B18C6 1:1:1 complexes with the alkali metal perchlorates follows the regular solution theory. For the diluent with a high dipole moment, however, the 1:1:1 complexes somewhat undergo the dipole-dipole interaction. B18C6 always shows very high extraction selectivity for KClO(4) over NaClO(4), which is determined mostly by the much greater log/(log K(MLA)) value for K(+) than for Na(+). The extraction-ability and -selectivity of B18C6 for Na(+) and K(+) ions with a perchlorate ion were compared with those with a picrate ion in terms of the fundamental equilibrium constants. The K(+) extraction-selectivity of B18C6 over Na(+) for the perchlorate system is superior to that for the picrate one, which is caused largely by the greater log/(log K(K(B18C6)A))-log/(log K(Na(B18C6)A)) value for the perchlorate than for the picrate. The perchlorate system is recommended for extraction separation of K(+) from Na(+).
为了定量研究阴离子对苯并 -18-冠 -6（B18C6）萃取碱金属离子的能力和选择性的影响，在25℃下测定了B18C6 - 高氯酸钠和高氯酸钾1:1:1配合物（MLA）在各种低介电常数稀释剂中的总萃取常数（K(ex)）以及在水相中形成离子对的常数（K(MLA)）。通过四个基本平衡常数对K(ex)值进行了分析。将我们已建立的方法应用于该高氯酸盐萃取体系来测定K(MLA)值。高氯酸盐的K(M(B18C6)A)值对于K⁺ 比对Na⁺ 大得多，并且比苦味酸盐的K(M(B18C6)A)值小得多。K(M(B18C6)A)值对高氯酸盐体系的K(ex)大小贡献较小，但对苦味酸盐体系的K(ex)贡献较大。B18C6与碱金属高氯酸盐的1:1:1配合物的分配行为遵循正规溶液理论。然而，对于具有高偶极矩的稀释剂，1:1:1配合物会发生一定程度的偶极 - 偶极相互作用。B18C6对KClO₄ 相对于NaClO₄ 始终表现出非常高的萃取选择性，这主要由K⁺ 的log/(log K(MLA))值比对Na⁺ 的大得多所决定。从基本平衡常数的角度比较了B18C6对高氯酸根离子存在下的Na⁺ 和K⁺ 离子的萃取能力和选择性与苦味酸根离子存在下的情况。B18C6在高氯酸盐体系中对K⁺ 相对于Na⁺ 的萃取选择性优于苦味酸盐体系，这主要是因为高氯酸盐的log/(log K(K(B18C6)A)) - log/(log K(Na(B18C6)A))值比苦味酸盐的大。推荐使用高氯酸盐体系从Na⁺ 中萃取分离K⁺ 。
