Diffusion of Organic Solute in Nanometer-sized Pores

Kinetic analysis of intraparticle mass transfer of a solute is generally performed for a arge number of particles. However, since the intraparticle mass transfer depends on the particle size, particle-particle distance, and so forth, measurements for single microparticles are indispensable for the quantitative analysis. Thus, microspectroscopy combined with microcapillary injection and manipulation technique has been developed, and the intraparticle mass transfer has been investigated on the basis of the direct measurements of extraction and release rates of a solute for single porous microparticles. In this review, the principles of the microcapillary manipulation-microspectroscopy technique and the diffusion of an organic solute in nanometer-sized pores of single ODS-silica gel and silica gel microparticles are described. The diffusion in the nanometer-sized pores is discussed in terms of pore and surface diffusion, slow desorption from the pore walls, and so on.