The intrinsic dissolution rate (IDR) is an important
parameter
in pharmaceutical science that measures the rate at which a pure crystalline
active pharmaceutical ingredient dissolves in the absence of diffusion
limitations. Traditional IDR measurement techniques do not capture
the complex interplay between particle morphology, fluid flow, and
dissolution dynamics. The dissolution rate of individual particles
can differ from the population average because of factors such as
particle size, surface roughness, or exposure of individual crystal
facets to the dissolution medium. The aim of this work was to apply
time-resolved X-ray microtomography imaging and simultaneously measure
the individual dissolution characteristics of a large population of
crystalline particles placed in a packed bed perfused by the dissolution
medium. Using NaCl crystals in three different size fractions as a
model, time-resolved microtomography made it possible to visualize
the dissolution process in a custom-built flow cell. Subsequent 3D
image analysis was used to evaluate changes in the shape, size, and
surface area of individual particles by tracking them as they are
dissolved. Information about the particle population statistics and
intrabatch variability provided a deeper insight into the dissolution
process that can complement established IDR measurements.