Effect of solvent type on preparation of ethyl cellulose microparticles by solvent evaporation method with double emulsion system using focused beam reflectance measurement

Abstract

The purpose of this study was to investigate effect of solvent type on solidification rate of ethyl cellulose (EC) microparticles and particle size/distribution of the emulsion droplets/hardened microparticles during solvent evaporation process using focused beam reflectance measurement (FBRM). EC microparticles were prepared by a W/O/W-solvent evaporation method using various solvents, including dichloromethane, dichloromethane:methanol (1:1), ethyl acetate and chloroform. The particle size/distribution of the emulsion droplets/hardened microparticles was monitored by FBRM. The morphology of EC microparticles was characterized by scanning electron microscopy (SEM). The transformation of the emulsion droplets into solid microparticles for all solvents occured within the first 10-90 min. The square weighted mean chord length of EC microparticles which were prepared using chloroform was smallest, but the chord counts was no the highest. The chord length distribution (CLD) measured by FBRM showed that a larger particle size mean gave longer CLD and a lower peak of particle number. SEM data revealed that the morphology of microparticles was influenced by type of solvent. FBRM can be employed for online monitoring of the shift in the microparticle CLD and detect transformation of the emulsion droplets into solid microparticles during the solvent evaporation process. The microparticle CLD and transformation process was strongly influenced by solvent type.