Cryogenically Cooled Adsorbent Trap for Off-Line Supercritical Fluid Extraction

The off-line collection of extracted analytes after supercritical fluid extraction (SFE) is an important step for successful extraction. Percent recoveries of various analytes using three different methods of off-line collection are reported. Poor collection efficiency is shown when the sample was collected in an empty vial. High collection efficiency (> 90%) of standards in a vial with the solvent is obtained only when a low flow rate of liquid CO2 (< 1 mL/min) is passed through the extraction vessel. Collection of the same analytes in a cryogenically cooled vessel filled with adsorbent shows an efficiency of greater than 90%. The flow rate of liquid CO2 through an extraction vessel does not have any effect on the collection efficiency. Collection of volatile analytes in a cryogenically cooled adsorbent trap requires low temperature trapping (< −40°C). Also, the type of liquid solvent used to wash the extracted analytes in a cryogenically cooled adsorbent trap is of importance.