(190e) Laser Induced Fluorescnce Studies of Concentration Fields in Supercritical Antisolvent Precipitation Process Spray

The supercritical antisolvent (SAS) precipitation process has received significant attention as a means of producing micro- and nano- particles for a variety of applications, such as pharmaceutical compounds, polymers and superconductor precursors. Despite wide variations in operating conditions and spray characteristics in SAS systems, resulting particles are generally found to be quite similar in size and size distribution. To better control this precipitation process and the size of resulting particles, a clearer understanding of the mass transfer and concentration fields in this process is required. To this end, we have employed planar laser induced fluorescence (PLIF) studies within the SAS precipitation process using a fluorescent molecule, Poly[methylmethacrylate-co-(7-(4-trifluoromethyl)coumarin methacrylamide)], as the solute in a solvent acetone with compressed carbon dioxide as the antisolvent. A laser plane (wavelength~337.1nm) through a sapphire window on the side of the precipitation vessel causes the solute to fluoresce thereby allowing visualization of its location and concentration within the SAS spray. A high magnification imaging technique is used to record the LIF for various regions of interest in the spray. In our previous work, a high magnification visualization system was used to study the spray characteristics and the micro particles formed in the SAS precipitation process for a solution of polymethyl methacrylate in acetone processed via SAS using compressed carbon dioxide. The spray characteristics and fluorescence fields were determined for several process conditions by visualizing the spray at various distances from the nozzle outlet through the transparent windows on the front and back of the precipitation vessel. The precipitated particles from both of these studies were collected and analyzed with a scanning electron microscope and a particle size distribution analysis was performed. The results from PLIF studies are coupled with the PMMA in acetone studies to relate process conditions and particle properties.