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A New Method for the Study of Processes at the Liquid–Liquid Interface Using an Array of Microdroplets on a Au Electrode
Author(s) -
Simm Andrew O.,
Chevallier François G.,
Ordeig Olga,
del Campo F. Javier,
Munoz Francesc X.,
Compton Richard G.
Publication year - 2006
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.200600394
Subject(s) - partition coefficient , chemistry , diffusion , aqueous solution , electrode , analytical chemistry (journal) , phase (matter) , aqueous two phase system , inert , liquid liquid , partition (number theory) , coating , thermodynamics , chromatography , organic chemistry , physics , mathematics , combinatorics
Abstract We report the fabrication of partially blocked gold electrodes, with regularly and hexagonally spaced inert hydrophobic blocks on their surface. The hydrophobic blocks, with diameters of 5 μm, are used to support liquid 5‐nonyl‐salicylaldoxime (Acorga‐P50) droplets on the surface. By voltametrically monitoring the transport‐controlled reduction rate of Cu II (in pH 5 solution) at the unblocked part of the gold surface it is possible to deduce, via simulation, the parameters controlling the rate of uptake of Cu II at the droplet–aqueous solution interface as the droplet “fills up” with Cu II . Experimentally, it is recorded that the reduction current increases until the droplet is filled completely; after this, there is no further noticeable effect of the droplet coating. A rigorous theoretical analysis of the transients permits the deduction of partition coefficients between the aqueous solution and the organic‐droplet phase and of diffusion coefficients within the droplet. The partition coefficient for Cu II between water and 5‐nonyl‐salicylaldoxime was found to be 200 at 25 °C and the diffusion coefficient of Cu II inside the organic phase was determined to be 5×10 −11 cm 2 s −1 .