V. Lopezavila et al., MICROWAVE-ASSISTED EXTRACTION OF ORGANIC-COMPOUNDS FROM STANDARD REFERENCE SOILS AND SEDIMENTS, Analytical chemistry, 66(7), 1994, pp. 1097-1106
As part of an ongoing evaluation of new sample preparation techniques
by the U.S. Environmental Protection Agency (EPA), especially those th
at minimize waste solvents, microwave-assisted extraction (MAE) of org
anic compounds from solid materials (or ''matrices'') was evaluated. S
ix certified reference materials containing polynuclear aromatic hydro
carbons (PAHs) and a few base/neutral/acidic compounds all of which ar
e 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-degrees-C) and for different periods of
time (5, 10, and 20 min). For comparison, the same samples were subje
cted 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 a
verage recovery at room temperature was approximately 52%, the MAE rec
overies for the 17 PAHs (3 of which were deuterated PAHs that were spi
ked into these matrices) from the six matrices were 70% at 80-degrees-
C, 75% at 115-degrees-C, and 75% at 145-degrees-C. Although the averag
e recoveries increased slightly with extraction time, the increase was
not statistically significant. The performance of the technique varie
d 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 approximately 50%. The spiked-compou
nd 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 alternativ
e to the conventional Soxhlet/Soxtec and sonication techniques. The MA
E technique requires smaller amounts of organic solvents, and sample t
hroughput is increased by shorter extraction times (10 min) and by sim
ultaneous extraction of up to 12 samples.