Liquid collection efficiencies after supercritical fluid extraction

Abstract

The design of any supercritical fluid extraction (SFE) experiment should break down into two parts: 1) removal of the analytes of interest from the bulk matrix and 2) deposition of those analytes in a user friendly manner for further studies (spectroscopy or chromatography). While great attention has been paid to the extraction of analytes, less attention has been paid for their efficient collection after extraction. Currently solid phase trapping and liquid trapping are available for off-line collection of analytes after SFE.

A polarity test mix consisting of acetophenone, <i>N,N</i>-dimethylaniline, naphthalene, <i>n</i>-decanoic acid, 2-naphthol, and <i>n</i>-tetracosane was spiked onto sand and extracted with supercritical carbon dioxide to evaluate the collection efficiency of various solvents and solvent mixtures. Nine single collection solvents and four mixed collection solvent systems were studied. When one-component collection solvents were employed, quantitative (above 90%) recovery of all analytes was not possible. With mixed collection solvents, recoveries of 90% or better with all analytes were possible.

Additional studies were performed with carbon dioxide modified with 1, or 4% acetonitrile or 1, 4, or 8% methanol or toluene. With these extraction fluids, quantitative collection of the analytes with a mixed collection solvent was not possible, but excellent collection efficiencies were observed for hexane and methanol collection.