Extraction of organic compounds from soil 5
accelerated solvent extraction gave essentially equivalent recoveries of chlorinated
dibenzo-p-dioxins and dibenzofurans from soil to Soxhlet extraction, but in less time
and using much less solvent.
1.3 PRESSURISED LIQUID EXTRACTION
Pressurised hot water extraction has been used in isolate polycyclic aromatic hydrocarbons from soil [49, 50]. Ramos et al [51] reported a rapid (ten minutes) miniaturised
pressurised liquid extraction method using only 100 µl solvent for extracting polycyclic
aromatic hydrocarbons from soil.
1.4 MICROWAVE-ASSISTED EXTRACTION
Lopez-Avila et al [52] showed that microwave-assisted extraction of pesticides and
polycyclic aromatic hydrocarbons from soil is a viable alternative to Soxhlet extraction
and needs a smaller sample volume and extraction time [54, 55]. These techniques
have also been compared in the case of chlorophenols. Lopez-Avila et al [53] compared
microwave-assisted extraction with electron capture gas chromatography to ELISA for
the determination of polychlorinated biphenyls in soils. Both techniques are applicable
to field screening and monitoring applications. Microwave-assisted extraction [56, 57]
and solid-phase microextraction [58] have been applied to the extraction of pesticides
from soil. It was observed by these and other workers [59] that the selectivity of
microwave-assisted extraction is highly dependent on the soil composition.
Micro-wave assisted extraction [60, 65–67] has been compared with ultrasonic
extraction [61] in the context of soil extraction. Microwave-assisted extraction [62]
and supercritical fluid extraction coupled with on-line infrared spectroscopy detection
[63, 64] have been compared as methods for the extraction of hydrocarbons from soil.
Dinaitoiu et al [68] developed a new method for volatile organic compounds
(VOCs) extraction from low-permeability media, such as clay, using trichloroethylene
(TCE) as a model compound. The method is based on microwave-assisted extraction
(MAE), which uses microwave energy to heat the extracting solvent and the sample,
MAE allows the extraction process to be carried out at elevated temperatures and
pressures, which dramatically reduces the time required to complete the process. A
PTFE vessel was used for extraction investigations. TCE analysis was performed using
gas chromatography with electron capture detection. Three different solvents were
tested: methanol, 1:1 hexane: acetone mixture, and 10:1 hexane: acetone mixture. A
comparison of TCE recoveries from clay samples using this method and the standard
methanol extraction method was carried out. The newly developed method and the
method currently in use were found to recover similar amounts of TCE. The major
advantage of the MAE technique the very short time needed to obtain complete analyte recovery (6–10 min), which makes it possible to analyse a large number of samples
without the need for sample preservation or prolonged storage. Thus, the new method
is much more efficient than the existing methods and has good potential for field
application.
accelerated solvent extraction gave essentially equivalent recoveries of chlorinated
dibenzo-p-dioxins and dibenzofurans from soil to Soxhlet extraction, but in less time
and using much less solvent.
1.3 PRESSURISED LIQUID EXTRACTION
Pressurised hot water extraction has been used in isolate polycyclic aromatic hydrocarbons from soil [49, 50]. Ramos et al [51] reported a rapid (ten minutes) miniaturised
pressurised liquid extraction method using only 100 µl solvent for extracting polycyclic
aromatic hydrocarbons from soil.
1.4 MICROWAVE-ASSISTED EXTRACTION
Lopez-Avila et al [52] showed that microwave-assisted extraction of pesticides and
polycyclic aromatic hydrocarbons from soil is a viable alternative to Soxhlet extraction
and needs a smaller sample volume and extraction time [54, 55]. These techniques
have also been compared in the case of chlorophenols. Lopez-Avila et al [53] compared
microwave-assisted extraction with electron capture gas chromatography to ELISA for
the determination of polychlorinated biphenyls in soils. Both techniques are applicable
to field screening and monitoring applications. Microwave-assisted extraction [56, 57]
and solid-phase microextraction [58] have been applied to the extraction of pesticides
from soil. It was observed by these and other workers [59] that the selectivity of
microwave-assisted extraction is highly dependent on the soil composition.
Micro-wave assisted extraction [60, 65–67] has been compared with ultrasonic
extraction [61] in the context of soil extraction. Microwave-assisted extraction [62]
and supercritical fluid extraction coupled with on-line infrared spectroscopy detection
[63, 64] have been compared as methods for the extraction of hydrocarbons from soil.
Dinaitoiu et al [68] developed a new method for volatile organic compounds
(VOCs) extraction from low-permeability media, such as clay, using trichloroethylene
(TCE) as a model compound. The method is based on microwave-assisted extraction
(MAE), which uses microwave energy to heat the extracting solvent and the sample,
MAE allows the extraction process to be carried out at elevated temperatures and
pressures, which dramatically reduces the time required to complete the process. A
PTFE vessel was used for extraction investigations. TCE analysis was performed using
gas chromatography with electron capture detection. Three different solvents were
tested: methanol, 1:1 hexane: acetone mixture, and 10:1 hexane: acetone mixture. A
comparison of TCE recoveries from clay samples using this method and the standard
methanol extraction method was carried out. The newly developed method and the
method currently in use were found to recover similar amounts of TCE. The major
advantage of the MAE technique the very short time needed to obtain complete analyte recovery (6–10 min), which makes it possible to analyse a large number of samples
without the need for sample preservation or prolonged storage. Thus, the new method
is much more efficient than the existing methods and has good potential for field
application.