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The emulsion non-solvent addition method ( ENSA ) is a
techology of controlled release. The microspheres of controlled
releasewas prepared by polymer solution (Ethly Cellulose,EC )
containing drug (Aspirin solid particle) in this report. There
were six variables , including the viscosity of Ethyl
Cellulose ; the kinds of non-solvent ; the ratio of drug to
Cellulose concentration ; the agitation speed ; the dispersion
phase volume ; the concentration of active agent to be studied.
For quantitative analysis , we chose the orthogonal method to
get the important parameters: the yield, drug content ,
particle size distribution , the release of microspheres in
different PH value solutions andthe release kinetics model
would be discussed. The results presented that the most
important factor for yield was viscosity of EC. High viscosity
make the yield increase . Using higher agitation speed and
hexane for non-solvent caused the small particle size of
microsphere. The drug content was almost near the ideal value
if the particle size range was between 1 and 0.590 (mm). But
the big size particle (>1 mm) could keep the stable unit
release rate in both acid and basic sol- utions because of the
more thicker EC shell. We found that only the big size
particles matched the First Order Kintics Model.
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