Quantification of Ag(I) and kinetic analysis using ion-pair extraction across a liquid/liquid interface in a laminar flow by fluorescence microscopy

Abstract

To analyze the kinetics of complicate ion-pair extraction, we have utilized a microfluidic approach and fluorescence detection. We have already developed a Ag(I)-specific thia-crown ether as an ion-association reagent. Furthermore, a fluorescent anion was added to detect the generated complex of Ag(I), ion-association reagent, and the counteranion in the ion-pair extraction system. A two-phase laminar flow consisting of an aqueous liquid and an organic liquid in a microchannel was formed, and the relationship between the initial conditions and reaction rate was examined. The microfluidic device could realize a spatiotemporal approach to solvent extraction, because the traveling length along the interface corresponded to the reaction time. The rate-determining step was estimated according to ion-pair formation behavior. Furthermore, due to the miniaturized reaction volume in the microchannel, rapid extraction of Ag(I) was achieved. The microchannel width was optimized to carry out the rapid extraction of Ag(I). In the application of the microfluidic device, the quantification of Ag(I) was examined and exhibited good linearity in the range of 6.1×10−7–4×10−6M. The lower limit of detection was almost the same as for an atomic absorption spectrometer.