Voltammetry of ion transfer across a polarized room-temperature ionic liquid membrane facilitated by valinomycin: theoretical aspects and application.
Cyclic voltammetry is used to investigate the transfer of alkali-metal cations, protons, and ammonium ions facilitated by the complex formation with valinomycin at the interface between an aqueous electrolyte solution and a room-temperature ionic liquid (RTIL) membrane. The membrane is made of a thin (approximately 112 microm) microporous filter impregnated with an RTIL that is composed of tridodecylmethylammonium cations and tetrakis[3,5-bis(trifluoromethyl)phenyl]borate anions. An extension of the existing theory of voltammetry of ion transfer across polarized liquid membranes makes it possible to evaluate the standard ion-transfer potentials for the hydrophilic cations studied, as well as the stability constants (K(i)) of their 1:1 complexes with valinomycin, as log K(i) = 9.0 (H(+)), 11.1 (Li(+)), 12.8 (Na(+)), 17.2 (K(+)), 15.7 (Rb(+)), 15.1 (Cs(+)), and 14.7 (NH(4)(+)). These data point to the remarkably enhanced stability of the valinomycin complexes within RTIL, and to the enhanced selectivity of valinomycin for K(+) over all other univalent ions studied, compared to the conventional K(+) ion-selective liquid-membrane electrodes. Selective complex formation allows one to resolve voltammetric responses of K(+) and Na(+) in the presence of an excess of Mg(2+) or Ca(2+), which is demonstrated by determination of K(+) and Na(+) in the table and tap water samples.
Langmaier
Jan
J
J. Heyrovský Institute of Physical Chemistry of ASCR, v.v.i, Dolejskova 3, 182 23 Prague 8, Czech Republic.
Samec
Zdenek
Z
D052578:Ionic Liquids / Q000737:chemistry*; D007476:Ionophores / Q000494:pharmacology*; D007477:Ions / Q000737:chemistry*; D008566:Membranes / Q000737:chemistry* / Q000187:drug effects*; D013054:Spectrophotometry, Atomic; D013696:Temperature; D014634:Valinomycin / Q000494:pharmacology*
D052578:Ionic Liquids; D007476:Ionophores; D007477:Ions; D014634:Valinomycin