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Technical Note 208 1

Methods Optimization in Accelerated
Solvent Extraction (ASE®)

Technical Note 208

INTRODUCTION
Accelerated solvent extraction is an innovative sample

preparation technique that combines elevated temperature
and pressures with liquid solvents to achieve fast and
efficient removal of analytes from various matrices.
ASE has been demonstrated to be equivalent to existing
extraction methodologies such as Soxhlet and automated
Soxhlet for most RCRA (Resource Conservation and
Recovery Act) analytes from solid and semisolid matrices.
It meets the requirements of U.S. EPA Method 3545,
Pressurized Fluid Extraction.

ASE is a more efficient form of liquid solvent
extraction, so all of the principles inherent to that technique
apply. To achieve efficient extraction, proper sample
preparation techniques and operational parameters must
be selected. It is normally very easy to transfer an existing
solvent-based extraction method to ASE technology.
This technical note is a guide to optimize ASE
extraction methods.

SAMPLE PREPARATION
Sample preparation is an essential part of every

solvent-based extraction procedure. While many sample
types can be efficiently extracted without any pretreatment,
other samples will require some manipulation for an
efficient extraction to occur. As with Soxhlet, the ideal
sample for extraction is a dry, finely divided solid.
Unfortunately, many samples do not fit this description.
Whatever can be done to make the sample approach this
definition will have a positive impact on the extraction. In
general, the same sample preparation that is done prior to
Soxhlet or sonication extraction should be done prior to
extraction by ASE.

Grinding
For an efficient extraction to occur, the solvent must

make contact with the target analytes. The more surface
area that can be exposed in a sample, the faster this will
occur. Samples with large particle sizes should be ground
prior to extraction. Efficient extraction requires a minimum
particle size, generally smaller than 0.5 mm. Grinding can
be accomplished with a conventional mortar and pestle or
with electric grinders and mills. Because quantitative
transfer of ground material can be difficult, it is recom-
mended that a large, representative sample be ground,
and weighed portions of the ground sample be used for
extraction. Polymer samples must be in a ground state for
an efficient extraction of additive compounds. Compliant

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