The manner in which the presence of a solute can affect the mixing behavior of a solute, solvent and antisolvent in a supercritical antisolvent (SAS) micronization process is demonstrated. The mixing behavior was analyzed by applying a two-dimensional (2D) Raman scattering technique. Mole fraction and partial density distributions were measured for the CO2 antisolvent. The results originating from the optical investigations were correlated with the particle results. The experiments cover the variation of the solute concentration at fixed operating conditions of 10 MPa and 40 degrees C.