Application of fractal geometry to dissolution kinetic study of a sweetener excipient

In the context of relationship study between dissolution kinetic and particle morphology using the fractal geometry tool, we use a commercially available quality of saccharin powder. The characterization of molecular feature and image analysis study allows us to conclude to the statistic self-similarity of particles of four sieved particles size fractions, permitting the fractal approach. Calculation of reactive fractal dimension is performed using two forms of mass transfer equation: -dQ/dt=kQ(D(R)/3)DeltaC and -dQ/dt=k'R(D(R)-3)DeltaC, with DeltaC=(C(f)/[lnC(s)/(C(s)-C(f))]). Based on comparison of the surface fractal dimension D(S) on the two values of reactive fractal dimension D(R), a dissolution mechanism can be drawn: the dissolution starts at the whole surface of particles and is further governed by digging into holes that involve inner mass of particles. S.E.M. observations confirm this hypothesis. The confrontation between the D(R) values provided by the two ways of determination is essential for a good prediction of the mechanism.