Selective recognition of calcium ion through liquid membrane

The mole transport rate of alkaline earth metal ions through a bulk liquid membrane and a supported liquid membrane using a series of proton diionizab le acyclic polyethers was measured. Among alkaline earth metal ions, the ca lcium ion was observed to be selectively transported in both single and com petitive transport experiments. Potentiometric titration and solution calor imetric titration also gave calcium selectivity over other alkaline earth m etal ions. Acyclic polyether bearing a diethylene glycol unit and n-tetrade cyl lipophilic chain at the a position of carboxylic acid affords the best selectivity for the calcium ion in bulk and supported liquid membranes. (C) 1998 Academic Press.