tissues. The different cleanup techniques of the extracts will also be addressed, while
the last section will be dedicated to separation and detection techniques. Given the
lack of analytical methods in the literature, the determination of drugs in earthworms
will be only partially treated at the end of the chapter.
2 Most Common Extraction Techniques
2.1 Assisted Solvent Extraction (ASE)
Assisted solvent extraction (ASE) is also known as pressurized liquid extraction,
(PLE), pressurized fluid extraction (PFE), enhanced solvent extraction (ESE), or
high-pressure solvent extraction (HPSE). ASE and PLE are the most popular names.
It is considered as an advanced, reasonably uncomplicated extraction technique,
time saver, and easy to learn. Briefly, the samples are mixed with a proper cell matrix
and filled in the cell. Then the cell is placed in a carousel; the latter rotates
automatically in a way to put the cell in the oven chamber. After preheating the
oven chamber, the cell is filled with the extraction solvent and kept for an optimized
static time, under the desired temperature and pressure. Finally, a solvent containing
the extracted analytes is obtained and collected in a vial, while the cell is then
washed and purged with a nitrogen flow [8]. All of those steps constitute one cycle
and can be repeated several times. The number of cycles is also optimized during
method development.
It is usually employed at temperature above the boiling point of the used
extraction solvent, along with high pressure to keep the solvent in liquid state during
the extraction process. Further, solvent’s viscosity decreases as the temperature
increases, which enhances its ability to wet the matrix and solubilize the target
analytes [9]. Therefore, besides its rapid extraction process, ASE has the advantage
of less solvent consumption, less toxicity, more environmentally friendly, and
possibility automation. All of these criteria have made ASE popular in pharmaceutical extraction field. It has been successfully applied to a wide range of analytes and
pharmaceuticals since polar and non-polar solvents, or a mixture of solvents, may be
used [10], though many parameters need to be optimized in order to obtain the
highest analyte recoveries, such as solvent selection, temperature, pressure, extraction time, and other parameters such as extraction mode, extraction time, number of
cycles, cell matrix, and flush volume.
2.2 Ultrasound Solvent Extraction (USE)
Ultrasound solvent extraction is based on cavitation effect generated by ultrasound
radiations in a water bath. Usually solid samples and the extractant are mixed in a
centrifuge tube and placed into tube rack in the ultrasonic water bath. The ultrasound
Development of Methods for the Determination of PhACs in Soil/Earthworm/Crop. . .
421
the last section will be dedicated to separation and detection techniques. Given the
lack of analytical methods in the literature, the determination of drugs in earthworms
will be only partially treated at the end of the chapter.
2 Most Common Extraction Techniques
2.1 Assisted Solvent Extraction (ASE)
Assisted solvent extraction (ASE) is also known as pressurized liquid extraction,
(PLE), pressurized fluid extraction (PFE), enhanced solvent extraction (ESE), or
high-pressure solvent extraction (HPSE). ASE and PLE are the most popular names.
It is considered as an advanced, reasonably uncomplicated extraction technique,
time saver, and easy to learn. Briefly, the samples are mixed with a proper cell matrix
and filled in the cell. Then the cell is placed in a carousel; the latter rotates
automatically in a way to put the cell in the oven chamber. After preheating the
oven chamber, the cell is filled with the extraction solvent and kept for an optimized
static time, under the desired temperature and pressure. Finally, a solvent containing
the extracted analytes is obtained and collected in a vial, while the cell is then
washed and purged with a nitrogen flow [8]. All of those steps constitute one cycle
and can be repeated several times. The number of cycles is also optimized during
method development.
It is usually employed at temperature above the boiling point of the used
extraction solvent, along with high pressure to keep the solvent in liquid state during
the extraction process. Further, solvent’s viscosity decreases as the temperature
increases, which enhances its ability to wet the matrix and solubilize the target
analytes [9]. Therefore, besides its rapid extraction process, ASE has the advantage
of less solvent consumption, less toxicity, more environmentally friendly, and
possibility automation. All of these criteria have made ASE popular in pharmaceutical extraction field. It has been successfully applied to a wide range of analytes and
pharmaceuticals since polar and non-polar solvents, or a mixture of solvents, may be
used [10], though many parameters need to be optimized in order to obtain the
highest analyte recoveries, such as solvent selection, temperature, pressure, extraction time, and other parameters such as extraction mode, extraction time, number of
cycles, cell matrix, and flush volume.
2.2 Ultrasound Solvent Extraction (USE)
Ultrasound solvent extraction is based on cavitation effect generated by ultrasound
radiations in a water bath. Usually solid samples and the extractant are mixed in a
centrifuge tube and placed into tube rack in the ultrasonic water bath. The ultrasound
Development of Methods for the Determination of PhACs in Soil/Earthworm/Crop. . .
421