A quasi steady-model of the dissolution of a single prolate or oblate
spheroidal particle has been developed based on the exact solution of
the steady-state diffusion equation for mass transfer in an unconfined
media. With appropriate treatment of bulk concentration, the model can
predict the detailed dissolution process of a single particle in a
container of finite size. The dimensionless governing equations suggest
that the dissolution process is determined by three dimensionless
control parameters, initial solid particle concentration, particle
aspect ratio, and the product of specific volume of solid particles and
saturation concentration of the dissolved species. Using this model, the
dissolution process of felodipine particles in a broad range of space of
the three control parameters are analyzed and some characteristics are
identified. The effects of material properties indicated by the product
of specific volume and saturation concentration are also analyzed.