An overview of Pressurized Liquid Extraction
Pressurized Fluid Extraction (PFE) or Pressurized Liquid Extraction (PLE) is a new sample extraction method that employs liquid solvents at elevated temperatures and pressures to prepare samples for analysis by either gas chromatography or liquid chromatography. Pressurized liquid extraction is similar to Soxhlet extraction, except that during the extraction process the solvent condition inside the PLE cell approaches the supercritical region which results in more efficient extractions. The elevated temperature allows the sample to become more soluble and achieve a higher diffusion rate while the elevated pressure keeps the solvent below its boiling point. At elevated pressures and temperatures solvents can penetrate solid samples more efficiently which reduces solvent usage.
A pressurized liquid extraction when compared to a traditional Soxhlet extraction shows a reduction in extraction time to 22 minutes from 18 hours and a decrease of total organic solvent consumption to 80 mL or less of organic solvent from 300 mL.
To perform a pressurized liquid extraction, between 5 grams and 100 grams of sample is mixed with sodium sulfate, loaded in the extraction cell and capped with two filtration end fittings. The PLE™ system then automatically starts pressurizing and heating the samples. The pressure is maintained at 1500-3000 PSI, at a temperature of 70-200 ºC. The extracted solvent containing the target analytes is then automatically transferred to a concentration/evaporation vessel where it is brought to final volume directly in a gas chromatography (GC) or liquid chromatography (LC) vial. The vial can then be transferred to the analytical instrument for final analysis.