Improved solvent trapping of volatiles in supercritical fluid extraction by pressurizing the collection vial
The high flow rates that result after decompression make the trapping of analytes one of the more difficult aspects of a supercritical extraction. By elevation of the pressure on the collection vial, the flow may be reduced and trapping efficiency improved, considerably. The effects of different collection vial pressures were evaluated. The best results were obtained at 25 atm. With the collection vial at 25 atm, the trapping efficiencies of different solvents were then investigated. Also considered were the effects of solvent volume, extraction flow rate, collection solvent geometry, and restrictor temperature. For a 30 min extraction--with the restrictor line at 200 degrees C--quantitative recoveries were obtained with analytes as volatile as chlorobenzene (approximately 90%) in 1 mL of solvent. Mild precooling of the collection vessel allowed quantitative recoveries to be obtained down to benzene (94.2%).
Stone
MA
Department of Chemistry, Virginia Polytechnic Institute and State University, Blacksburg 24061-0212, USA.
Taylor
LT