Homogeneous oligo(oxyethylene)
n-dodecyl ethers(C
12E
m,
m=28)and higher alkanoic acids(C
8C
18)were examined as carriers for the competitive passive transport of alkali(Li
+, Na
+, and K
+)and alkaline earth metal(Mg
2+, Ca
2+, and Ba
2+)cations through a chloroform membrane.
1) The linear polyethers, combined with an alkanoic acid, effectively mediated cation-transport similarly to cooperative carriers composed of crown ether and alkanoic acid as reported previously
l4)16).
2) 2-Bromoalkanoic acids (BAA) were superior to those unsubstituted as co-carriers in both transport efficiency and cation-selectivity for two competitive systems (Table-1 and -2).
3) For a monovalent cations system, the polyethers combined with BAA (C
12E
m-BAA) had essentially the same selectivity (K
+>Na
+>>Li
+). Their transport efficiency increased with
m (Fig.-3).
4) The selectivity of divalent cations except Mg
2+ was found to depended on
m of C
12E
m-BAA, and plots of efficiency
vs. m for Ca
2+ and Ba
2+ gave maxima at
m=5 and
m=6, respectively (Fig.-5).
5) The effect of the acyl chain length of BAA on the transport ability of these cooperative carriers was also examined (Fig.-4 and -6).
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