Phenytoin crystal growth rates in the presence of phosphate and chloride ions

Phenytoin crystal growth kinetics have been measured as a function of supersaturation in pH 2.2 phosphoric acid and pH 2.2 hydrochloric acid solutions. Two different methods were used for the kinetic analysis. The first involved a zone-sensing device which provided an analysis of the distribution of crystals in a batch crystallizer. Crystal growth rates were calculated from the increase in the size of the distribution with time. In the second method, growth rates were evaluated from the change in size with time of individual crystals observed under an inverted microscope. The results from each method compare favorably. The use of both techniques provides an excellent opportunity to exploit the strengths of each: an average growth rate from a population of crystals from batch crystallization and insight into the effect of growth on the morphology of the crystals from the individual crystal measurements.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29867/1/0000215.pd

The mechanism of phenytoin crystal growth

Phenytoin crystal growth kinetics have been measured as a function of pH, supersaturation and temperature in phosphate buffer. Incorporation of growth units into the crystal lattice was not influenced by diffusion from the bulk to the solid surface. Thus, the rate limiting step for phenytoin growth is surface integration. Phenytoin crystal growth is via a screw-dislocation mechanism; this mechanism explains the observed dependence of growth rate on supersaturation and the increase in growth rate with pH.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30628/1/0000269.pd