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Supercritical Fluid Extraction of Organics in Environmental Analysis

Environment: Water and Waste

  1. Bruce A. Benner Jr

Published Online: 15 SEP 2006

DOI: 10.1002/9780470027318.a0871

Encyclopedia of Analytical Chemistry

Encyclopedia of Analytical Chemistry

How to Cite

Benner, B. A. 2006. Supercritical Fluid Extraction of Organics in Environmental Analysis. Encyclopedia of Analytical Chemistry. .

Author Information

  1. National Institute of Standards and Technology, Gaithersburg, USA

Publication History

  1. Published Online: 15 SEP 2006

Abstract

Supercritical fluids (SFs) possess several physical properties that make them attractive substitutes for conventional liquid solvents in analytical-scale extractions. Molecular diffusivities of SFs are typically a factor of 10 greater (10−4 vs 10−5 cm2 s−1) and their viscosities are a factor of 10 lower (10−4 vs 10−3 N s m−2) than liquid solvents. These properties improve the rate of mass transfer of a solute from the matrix surface to the bulk extractions fluid – a transfer believed to be the rate-limiting step of most extractions. Under optimized conditions, the improvements in mass transfer can enable a supercritical fluid extraction (SFE) to be completed in less than 1 h compared to ≥12 h for extractions involving conventional solvent techniques. The typical SFE also generates little solvent waste, compared to traditional extraction methods, but limitations have also emerged with respect to the efficiency of SFE as related to the sample composition (matrix effect). This review will discuss the progress made over the last 20 years in SFE as an alternative technique to liquid solvent extractions of environmental samples for the subsequent measurement of organic constituents.