title: Ionophore-based ion-exchange emulsions as novel class of complexometric titration reagents.
abstract: Complexometric titrations rely on a drastic change of the pM value at the equivalence point with a water soluble chelator forming typically 1 : 1 complexes of high stability. The available chemical toolbox of suitable chelating compounds is unfortunately limited because many promising complexing agents are not water soluble. We introduce here a novel class of complexometric titration reagents, a suspension of polymeric nanospheres whose hydrophobic core is doped with lipophilic ion-exchanger and a selective complexing agent (ionophore). The emulsified nanospheres behave on the basis of heterogeneous ion exchange equilibria where the initial counter ion of the ion-exchanger is readily displaced from the emulsion for the target ion that forms a stable complex in the nanosphere core. Two different examples are shown with Ca(2+) and Pb(2+) as target ions. The lack of protonatable groups on the calcium receptor allows one to perform Ca(2+) titration without pH control.
authors.affiliation: University of Geneva, 30 Quai Ernest Ansermet, 1211 Geneva 4, Switzerland. eric.backker@unige.ch.
authors.forename: Jingying
authors.initials: J
authors.lastname: Zhai
authors.forename: Xiaojiang
authors.initials: X
authors.lastname: Xie
authors.forename: Eric
authors.initials: E
authors.lastname: Bakker