Extraction of surfactants from aqueous media by supercritical fluid extraction

Two methods for the supercritical fluid extraction (SFE) of analytes from aqueous media were evaluated: direct extraction and solid-phase extraction (SPE) discs. SPE discs were used to isolate an alcohol phenol ethoxylate (APE) non-ionic surfactant from an aqueous matrix prior to extraction using supercritical CO2. This method was compared with the direct SFE of surfactant from the aqueous matrix. The second method allowed the continuous extraction of analyte from water using a modified extraction cell. The extraction cell was designed to maximize the exposure of the analyte to supercritical CO2 interactions and thereby allow the continuous extraction of the analyte from an aqueous sample. The results suggest that there is a difference in the effects of diffusion and equilibrium on the extraction process for the two methods of extraction studied.