Dry-spraying of ascorbic acid or acetaminophen solutions with supercritical carbon dioxide

Carbon dioxide is a very poor solvent for many organic compounds, which makes it a good anti-solvent. When a solution is sprayed into carbon dioxide vapour the anti-solvent reduces the solubility within several tens of milliseconds and the solute precipitates. Two distinct regions can be identified, below and above the mixture critical pressure. Below this critical pressure the yield remains relatively low and the process is not well controlled. Above the critical pressure small crystals are obtained of about 2 mu m with a yield of 90%. (C) 1999 Elsevier Science B.V. All rights reserved.