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MICROWAVE-ASSISTED EXTRACTION OF ORGANIC COMPOUNDS FROM STANDARD REFERENCE SOILS AND SEDIMENTS
Citation:
Lopez-Avila, V., R. Young, AND W. Beckert. MICROWAVE-ASSISTED EXTRACTION OF ORGANIC COMPOUNDS FROM STANDARD REFERENCE SOILS AND SEDIMENTS. Analytical Chemistry 66(7):1097-1106, (1994).
Description:
As part of an ongoing evaluation of new sample preparation techniques by the U.S. Environmental Protection Agency (EPA), especially those that minimize waste solvents, microwave-assisted extraction (MAE) of organic compounds from solid materials (or "matrices") was evaluated. Six certified reference materials containing polynuclear aromatic hydrocarbons (PAHs) and a few base/neutral/acidic compounds, all of which are common pollutants of interest to the EPA, were subjected to MAE in a closed-vessel microwave system with hexane/acetone (1:1) at different temperatures (80,115, and 145 C) and for different periods of time (5,10, and 20 min.) For comparison, the same samples were subjected to room-temperature extraction by allowing the solvent mixture to stay in contact with the solid matrix the same amount of time as the microwave-extracted sample (including any cooling time). Whereas the average recovery at room temperature was~52%, the MAE recoveries for the 17 PAHs (3 of which were deuterated PAHs that were spiked into these matrices) from the six matrices were 70% at 80 C, 75% at 115 C, and 75% at 145 C. Although the average recoveries increased slightly with extraction time, the increase was not statistically significant. The performance of the tecnique varied with the matrix and the analyte. Eleven PAHs had average recoveries in the 65-85% range, and three compounds (acenaphthene, benzo[a]pyrene, and fluorene) had recoveries of ~ 50%. The spiked-compound recoveries were 77% for acenaphthene-d10, 105% for fluoranthene-d10, and 85% for benzo[a]anthracene-d12. Experiments with 14 phenols and 20 organochlorine pesticides indicated that MAE is a viable alternative to the coventional Soxhlet/Soxtec and sonication techniques. The MAE technique requires smaller amounts of organic solvents, and sample throughput is increased by shorter extraction times (10 min) and by simultaneous extraction of up to 12 samples.