A new method for the study of processes at the liquid-liquid interface using an array of microdroplets on a au electrode.
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 mum, 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 degrees C and the diffusion coefficient of Cu(II) inside the organic phase was determined to be 5 x 10(-11) cm2 s(-1).
Simm
Andrew O
AO
Physical and Theoretical Chemistry Laboratory, Oxford University, South Parks Road, Oxford OX1 3QZ, UK.
Chevallier
François G
FG
Ordeig
Olga
O
del Campo
F Javier
FJ
Munoz
Francesc X
FX
Compton
Richard G
RG
D003300:Copper / Q000737:chemistry*; D004566:Electrodes; D006046:Gold / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D010091:Oximes / Q000737:chemistry*; D010316:Particle Size; D013499:Surface Properties; D013696:Temperature
D010091:Oximes; C493612:5-nonylsalicylaldoxime; D006046:Gold; D003300:Copper