In this work, a new modification of the supercritical carbon dioxide antisolvent precipitation (SAS) process has been used to allow the processing of hydrosoluble compounds; carbon dioxide mixtures with ethanol, used at expanded liquid conditions, allowed to produce micro and nanoparticles of two model water-soluble materials: yttrium acetate (YAc) and bovine serum albumin (BSA). The effect of the process parameters, such as composition of the antisolvent, concentration of the aqueous solution, washing time and injector diameter on the morphology and on the dimensions of the precipitates was investigated. Selecting the appropriate operating conditions, spherical non-coalescing particles were produced. In particular, BSA microparticles with narrow particle size distributions and the mean diameter in the range 0.5-2 mu m and BSA nanoparticles with a mean diameter down to 0.19 mu m were produced. (C) 2012 Elsevier E.V. All rights reserved.