単一オクタデシルシリルシリカゲル微粒子/水系における界面活性剤の移動過程の顕微蛍光分析単一オクタデシルシリルシリカゲル微粒子/水系における界面活性剤の移動過程の顕微蛍光分析AN00222633 Fluorescence Microspectroscopic Analysis of Surfactant Transfer in the Single Octadecylsilyl Silica Gel Microparticle/Water System
The mass transfer of 4-(1,1,3,3-tetramethylbutyl)phenyl polyethylene glycol (Triton X-100, TX-100) as a nonionic surfactant in the octadecylsilyl (ODS) silica gel/water system was investigated using coumarin 102, known as a solvatochromic dye, by the single microparticle manipulation-fluorescence microspectroscopy technique. A spherical ODS silica gel microparticle (particle radius (r) of 10–30 μm, pore diameter of 12 nm) including coumarin 102 was injected into an aqueous TX-100 solution, and the release rate of the dye from the microparticle into the aqueous phase was measured by a confocal fluorescence microscope. The intraparticle diffusion rates of the dye and TX-100 were much faster than the release rate of the dye. The release rate of the dye was discussed using the time dependence of the total fluorescence intensity (IF). An induction period for IF was observed in the short time region. After the induction period, IF could be analyzed on the basis of the first-order reaction-type equation, and the rate-constant values agreed with those for the release of the dye at the sorption equilibrium of TX-100. In the induction period, the fluorescence maximum of the dye depended on time. Therefore, we consider that the sorption of TX-100 proceeds in the induction period. Because the inverse of the time of the induction period was directly proportional to r−2, we conclude that the rate-determining step of the sorption rate of TX-100 is the diffusion between the bulk water phase and the spherical surface of the microparticle.